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Effects of Stimulants and the Brain on the Central Nervous System Back to Course Index




Introducing the Human Brain

The human brain is the most complex organ in the body. This three-pound mass of gray and white matter sits at the center of all human activity – you need it to drive a car, to enjoy a meal, to breathe, to create an artistic masterpiece, and to enjoy everyday activities. In brief, the brain regulates your basic body functions; enables you to interpret and respond to everything you experience; and shapes your thoughts, emotions, and behavior.

The brain is made up of many parts that all work together as a team. Different parts of the brain are responsible for coordinating and performing specific functions. Drugs can alter important brain areas that are necessary for life-sustaining functions and can drive the compulsive drug abuse that marks addiction. Brain areas affected by drug abuse:

      The brain stem controls basic functions critical to life, such as heart rate, breathing, and sleeping.

      The limbic system contains the brain’s reward circuit – it links together a number of brain structures that control and regulate our ability to feel pleasure. Feeling pleasure motivates us to repeat behaviors such as eating – actions that are critical to our existence. The limbic system is activated when we perform these activities – and also by drugs of abuse. In addition, the limbic system is responsible for our perception of other emotions, both positive and negative, which explains the mood-altering properties of many drugs.

The cerebral cortex is divided into areas that control specific functions. Different areas process information from our senses, enabling us to see, feel, hear, and taste. The front part of the cortex, the frontal cortex or forebrain, is the thinking center of the brain; it powers our ability to think, plan, solve problems, and make decisions.


The Central Nervous System (CNS)

The central nervous system (CNS) coordinates the functions of all parts of the body and consists of the brain and the spinal cord, as well as the retina. Together with the peripheral nervous system, it has a fundamental role in the control of behavior. The CNS is contained within the dorsal cavity, with the brain in the cranial cavity and the spinal cord in the spinal cavity.  The brain is protected by the skull, while the spinal cord is protected by the vertebrae, and both are enclosed in the meninges.

The brain receives sensory input from the spinal cord as well as from its own nerves (e.g., olfactory and optic nerves) and devotes most of its volume to processing its various sensory inputs and initiating appropriate and coordinated motor outputs.  Whereas, the spinal cord conducts sensory information from the peripheral nervous system (both somatic and autonomic) to the brain and transmits motor information from the brain to our various effectors such as skeletal muscles, cardiac muscle, and various glands.

The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions and transmit signals between different parts of the body.  The peripheral nervous system consists of sensory neurons, clusters of neurons called ganglia, and nerves connecting them to each other and to the central nervous system. These regions are all interconnected by means of complex neural pathways.

Neurons send signals to other cells as electrochemical waves traveling along thin fibers called axons, which cause chemicals called neurotransmitters to be released at junctions called synapses. A cell that receives a synaptic signal may be excited, inhibited, or otherwise modulated. Sensory neurons are activated by physical stimuli impinging on them, and send signals that inform the central nervous system of the state of the body and the external environment. Motor neurons situated either in the central nervous system or in peripheral ganglia, connect the nervous system to muscles or other effecter organs. Central neurons, which in vertebrates greatly outnumber the other types, make all of their input and output connections with other neurons. The interactions of all these types of neurons form neural circuits that generate an organism’s perception of the world and determine its behavior.

The brain and nervous system are made of billions of nerve cells, called neurons. Neurons have three main parts: cell body, dendrites, and axon. The axon is covered by the myelin sheath. The transfer of information between neurons is called neurotransmission. This is how neurotransmission works:

1. A message travels from the dendrites through the cell body and to the end of the axon.

2. The message causes the chemicals, called neurotransmitters, to be released from the end of the axon into the synapse. The neurotransmitters carry the message with them into the synapse. The synapse is the space between the axon of one neuron and the dendrites of another neuron.

3. The neurotransmitters then travel across the synapse to special places on the dendrites of the next neuron, called receptors. The neurotransmitters fit into the receptors like keys in locks.

4. Once the neurotransmitter has attached to the receptors of the second neuron, the message is passed on.

5. The neurotransmitters are released from the receptors and are either broken down or go back into the axon of the first neuron.

At the most basic level, the CNS sends signals from one cell to another or from one part of the body to another part. There are multiple ways that a cell can send signals to other cells. One is by releasing chemicals called hormones into the internal circulation, so that they can diffuse to distant sites. In contrast to this “broadcast” mode of signaling, the nervous system provides “point-to-point” signals neurons project their axons to specific target areas and make synaptic connections with specific target cells. Thus, neural signaling is capable of a much higher level of specificity than hormonal signaling. It is also much faster: the fastest nerve signals travel at speeds that exceed 100 meters per second.

At a more integrative level, the primary function of the nervous system is to control the body.  It does this by extracting information from the environment using sensory receptors, sending signals that encode this information into the central nervous system, processing the information to determine an appropriate response, and sending output signals to muscles or glands to activate the response. The evolution of a complex nervous system has made it possible for various animal species to have advanced perception abilities such as vision, complex social interactions, rapid coordination of organ systems, and integrated processing of concurrent signals. In humans, the sophistication of the nervous system makes it possible to have language, abstract representation of concepts, transmission of culture, and many other features of human society that would not exist without the human brain.

This continuing education course will focus on the area of psychoactive chemicals and the central nervous system.  The term psychoactive chemical simply means that a chemical has the capability to increase or decrease the speed of electrical impulses along the nervous system.  This is accomplished simply by altering the various bio-chemicals or neurotransmitters at the neuronal gaps or synapses.  For example, alcohol slows down this electrical activity while cocaine speeds up this electrical activity.

This is the second in a series of courses on the central nervous system and drugs.  The first course explored depressants; this course will discuss stimulants.



Psychoactive chemicals may be distinguished by their overall effects on the CNS.  The classifications of depressants, stimulants, psychedelics and others (inhalants, prescription drugs, etc.) are commonly used.  Psychoactive chemicals act on the brain by affecting various neurotransmitters (neurotransmitters are brain chemicals that facilitate communication between brain cells).  For example, CNS stimulants generally act on or increase the level of the neurotransmitter dopamine which affects the part of the brain that controls pleasure. It works by increasing the amount of dopamine in the brain.  Other classifications act on different neurotransmitters that are identified and discussed in other sections of this Continuing Education Course. 

CNS STIMULANTS (Excerpts were taken from the NIDA website)

CNS stimulants accelerate selected brain functions and alter others.  They can results in over-stimulation of the CNS that causes increased heart rate and respiration, increased blood pressure, insomnia, decreased appetite, and energized muscles.  Strong stimulants can also cause restlessness, anger, aggression behaviors and dilated pupils.  In small doses they also make the user more alert, active, anxious, restless, and in general more stimulated than normal. In large doses heart, blood vessel, and seizure problems may occur. 

Continued use over a few days will deplete the body’s energy chemicals and exhaust the user.  Caffeine and Nicotine are weak stimulants; however, their long-term use can be dangerous, causing such diseases as cancer, emphysema, and heart disease (nicotine causes the most severe long term health problem). The major categories of stimulants are:

        Cocaine:  Cocaine is a powerfully addictive stimulant that directly affects the brain. Cocaine was labeled the drug of the 1980s and 1990s because of its extensive popularity and use during that period.

        Amphetamines/methamphetamines: Amphetamines/methamphetamines are powerful, synthetic stimulants with effects similar to cocaine but much longer lasting and cheaper to use.  They can be taken orally but shooting and snorting are the most commune routes of administration.

        Caffeine:  Caffeine is the most popular stimulant in the world.  It is a very mild stimulant and is found in coffee, tea, soft drinks, chocolate, and in hundreds of over-the-counter and prescription medications.

        Nicotine:  Through the use of tobacco, nicotine is one of the most heavily used addictive drugs and the leading preventable cause of disease, disability, and death in the U.S. Cigarette smoking accounts for 90% of lung cancer cases in the U.S., and about 38,000 deaths per year can be attributed to secondhand smoke. Cigarettes and chew tobacco are illegal substances in most U.S. states for those under 18.

        OTC/Prescription/Miscellaneous:  Hundreds of cold and allergy medications contain Pseudoephedrine and phenylpropanolamine, which have decongestant, mild anorexic and stimulant effects.  They are often used in combination with antihistamines, such as Benadryl and diet medications.  Individuals who ingest these mediations and drink coffee or other caffeinated beverages often experience anxiety attacks and rapid heartbeats.




        Cocaine (Excerpts taken from NIDA Research report series)

Cocaine is a highly addictive stimulant and is one of the oldest psychoactive substances.  Coca leaves, the source of cocaine, have been chewed and ingested for thousands of years, and purified chemical, cocaine hydrochloride, has been an abused substance for more than 100 years.  Today cocaine is a schedule II drug, which means that it has a high potential for abuse but can be administered by a doctor for legitimate medical uses, such as local anesthesia for some eye, ear and throat surgeries.  In the early 1900s purified cocaine was the main active ingredient in most of the tonics and elixirs that were developed to treat a wide variety of illnesses.

Pure cocaine was originally extracted from the leaf of the Erythroxylon coca bush, which grew primarily in South America. Currently, Colombia is the largest grower of the coca bush.  Street dealers generally dilute the pure cocaine with inert substances such as cornstarch, talcum powder, or sugar or with active drugs such as procaine (a chemically related local anesthetic) or amphetamine (another stimulant). Some users combine cocaine with heroin in what is termed a speedball.

There are two forms of cocaine that are abused: the water-soluble hydrochloride salt and the water-insoluble cocaine base (or freebase). When abused, the hydrochloride salt, or powdered form of cocaine, can be injected or snorted. The base form of cocaine has been processed with ammonia or sodium bicarbonate (baking soda) and water, and then heated to remove the hydrochloride to produce a chemical that can be smoked. The term crack, which is the street name given to freebase cocaine, refers to the crackling sound heard when the mixture is smoked.

Cocaine use ranges from recreational (occasional) to compulsive. There is no safe way to use cocaine except under the supervision of a physician for medical purposes. Any route of administration can lead to absorption of toxic amounts of cocaine, possible acute cardiovascular or cerebral-vascular emergencies, and seizures all of which can result in sudden death.

Cocaine Abuse

The principal routes of cocaine administration are oral, intranasal, intravenous, and inhalation. Snorting or intranasal administration is the process of inhaling cocaine powder through the nostrils, where it is absorbed into the bloodstream through the nasal tissues.  Injecting or intravenous use releases the drug directly into the bloodstream and heightens the intensity of its effects. Smoking involves inhaling cocaine vapor or smoke into the lungs, where absorption into the bloodstream is as rapid as by injection. This rather immediate and euphoric effect is one of the reasons that crack became enormously popular in the mid-1980s.

Cocaine Effects

Cocaine is a strong central nervous system stimulant that increases levels of dopamine, a brain chemical (or neurotransmitter) associated with pleasure and movement, in the brains reward circuit. Certain brain cells, or neurons, use dopamine to communicate. Normally, dopamine is released by a neuron in response to a pleasurable signal (e.g., the smell of good food), and then recycled back into the cell that released it, thus shutting off the signal between neurons. Cocaine acts by preventing the dopamine from being recycled, causing excessive amounts of the neurotransmitter to build up, amplifying the message to and response of the receiving neuron, and ultimately disrupting normal communication. It is this excess of dopamine that is responsible for cocaine’s euphoric effects. With repeated use, cocaine can cause long-term changes in the brains reward system and in other brain systems as well, which may eventually lead to addiction. With repeated use, tolerance to the cocaine high also often develops. Many cocaine abusers report that they seek but fail to achieve as much pleasure as they did from their first exposure. Some users will increase their dose in an attempt to intensify and prolong the euphoria, but this can also increase the risk of adverse psychological or physiological effects.

Short-Term Effects of Cocaine Use

Cocaine’s effects appear almost immediately after a single dose and disappear within a few minutes to an hour. Taken in small amounts, cocaine usually makes the user feel euphoric, energetic, talkative, and mentally alert, especially to the sensations of sight, sound, and touch. It can also temporarily decrease the need for food and sleep. Some users find that the drug helps them perform simple physical and intellectual tasks more quickly, although others experience the opposite effect.

The duration of cocaine’s euphoric effects depend upon the route of administration. The faster the drug is absorbed, the more intense the resulting high, but also the shorter the duration. The high from snorting is relatively slow to arrive, but it may last from 15 to 30 minutes; in contrast, the effects from smoking are more immediate but may last only 5 to 10 minutes.

The short-term physiological effects of cocaine use include constricted blood vessels; dilated pupils; and increased body temperature, heart rate, and blood pressure. Large amounts of cocaine may intensify the users high but can also lead to bizarre, erratic, and violent behavior. Some cocaine users report feelings of restlessness, irritability, anxiety, panic, and paranoia. Users may also experience tremors, vertigo and muscle twitches.

There also can be severe medical complications associated with cocaine abuse. Some of the most frequent are cardiovascular effects, including disturbances in heart rhythm and heart attacks; neurological effects, including strokes, seizures, headaches, and coma; and gastrointestinal complications, including abdominal pain and nausea. In rare instances, sudden death can occur on the first use of cocaine or unexpectedly thereafter. Cocaine related deaths are often a result of cardiac arrest or seizures followed by respiratory arrest.

Long-Term Effects of Cocaine Use

With long term use of cocaine, the brain will adapt to an altered state and the reward pathway becomes less sensitive to natural stimuli and to the drug itself. Tolerance may develop this means that higher doses and/or more frequent use is needed to acquire the same level of pleasure experienced during initial use. At the same time, users can also become more sensitive (sensitization) to cocaine’s anxiety-producing and other toxic effects.

Users take cocaine in binges, during which the cocaine is used repeatedly and at increasingly higher doses. This can lead to increased irritability, restlessness, panic attacks, and paranoia even a full-blown psychosis, in which the individual loses touch with reality and experiences auditory hallucinations.

Different routes of administration can produce different adverse effects. Regularly snorting cocaine, for example, can lead to loss of sense of smell; nosebleeds; problems with swallowing; hoarseness; and an overall irritation of the nasal septum, which could result in a chronically inflamed, runny nose. Ingested cocaine can cause severe bowel gangrene due to reduced blood flow. Persons who inject cocaine have puncture marks called tracks, most commonly in their forearms, and may experience allergic reactions, either to the drug or to some additive in street cocaine, which in severe cases can result in death. Many chronic cocaine users lose their appetite and experience significant weight loss and malnourishment.

Polydrug use of more than one drug is common among substance abusers. When people consume two or more psychoactive drugs together, such as cocaine and alcohol, they compound the danger each drug poses and unknowingly perform a complex chemical experiment within their bodies. Researchers have found that the human liver combines cocaine and alcohol to produce a third substance, coca-ethylene, which intensifies cocaine’s euphoric effects. Coca-ethylene is associated with a greater risk of sudden death than cocaine alone.

Risk for Contracting HIV/AIDS and Hepatitis

Cocaine abusers are at increased risk for contracting such infectious diseases as human immunodeficiency virus/acquired immune deficiency syndrome (HIV/AIDS) and viral hepatitis. This risk stems not only from sharing contaminated needles and drug paraphernalia but also from engaging in risky behaviors as a result of intoxication. Research has shown that drug abuse can compromise judgment and decision making, and lead to risky sexual encounters, needle sharing, and trading sex for drugs by both men and women. In fact, some studies are showing that among drug abusers, those who do not inject drugs are contracting HIV at rates equal to those who do inject drugs, further highlighting the role of sexual transmission of HIV in this population.

Additionally, hepatitis C (HCV) has spread rapidly among injecting drug users. Risk begins with the first injection, and within 2 years, nearly 40 percent of injection drug users (IDUs) are exposed to HCV. By the time IDUs have been injecting for 5 years, their chances of being infected with HCV are between 50 and 80 percent. Although treatment for HCV is not effective for everyone and can have significant side effects, medical follow-up is essential for all those who are infected. There is no vaccine for the hepatitis C virus, and it is highly transmissible via injection; thus, HCV testing is recommended for any individual who has ever injected drugs.

Treatment Options

Behavioral interventions particularly, cognitive-behavioral therapy, have been shown to be effective for decreasing cocaine use and preventing relapse. Treatment must be tailored to the individual patients needs in order to optimize outcomes this often involves a combination of treatment, social supports, and other services.

Currently, there are no FDA-approved medications for treating cocaine addiction; thus, developing a medication to treat cocaine and other forms of addiction remains a top research priority. Researchers are seeking to develop medications that help alleviate the severe craving associated with cocaine addiction, as well as medications that counteract cocaine-related relapse triggers, such as stress. Several compounds are currently being investigated for their safety and efficacy, including a vaccine that would sequester cocaine in the bloodstream and prevent it from reaching the brain. Current research suggests that while medications are effective in treating addiction, combining them with a comprehensive behavioral therapy program is the most effective method to reduce drug use in the long term.



Amphetamines are a class of powerful, synthetic stimulants with effects similar to cocaine but much longer lasting and cheaper to use.  The street names include speed, meth, crank, crystal, ice, glass, and a multitude of others.  Amphetamines can be taken orally but shooting and snorting are the most commune routes of administration. Amphetamines often come in pill form and are sometimes prescribed by doctors for medical problems, most commonly attention deficit hyperactivity disorder (ADHD). Amphetamines can also be abused, that is, used in a way other than as prescribed (e.g., crushed and snorted) or used by someone without a prescription. 

Methamphetamine is also a powerful stimulant, originally derived from amphetamine. It comes in clear crystals or powder and easily dissolves in water or alcohol. Although most of the methamphetamine used in the United States comes from super labs, it is also made in small laboratories using inexpensive over-the-counter and often toxic ingredients (such as drain cleaner, battery acid, and antifreeze). Amphetamine congers (by products) are stimulant drugs which produce many of the same effects as amphetamines but are not as strong.  They are also chemically related to amphetamines.

Stimulant medications (e.g., methylphenidate and amphetamines) are often prescribed to treat individuals diagnosed with attention-deficit hyperactivity disorder (ADHD). ADHD is characterized by a persistent pattern of inattention and/or hyperactivity-impulsivity that is more frequently displayed and more severe than is typically observed in individuals at a comparable level of development. This pattern of behavior usually becomes evident in the preschool or early elementary years, and the median age of onset of ADHD symptoms is 7 years. For many individuals, ADHD symptoms improve during adolescence or as age increases, but the disorder can persist into adulthood. In the United States, ADHD is diagnosed in an estimated 8 percent of children ages 417 and about 3 percent of adults.

Affects on the Brain

All stimulants work by increasing dopamine levels in the brain dopamine is a brain chemical (or neurotransmitter) associated with pleasure, movement, and attention. The therapeutic effect of stimulants is achieved by slow and steady increases of dopamine, which are similar to the natural production of the chemical by the brain. The doses prescribed by physicians start low and increase gradually until a therapeutic effect is reached. However, when taken in doses and routes other than those prescribed, stimulants can increase brain dopamine in a rapid and highly amplified manner as do most other drugs of abuse disrupting normal communication between brain cells, producing euphoria, and increasing the risk of addiction.

Treatment of ADHD

Treatment of ADHD with stimulants, often in conjunction with psychotherapy, helps to improve the symptoms of ADHD, as well as the self-esteem, cognition, and social and family interactions of the patient. The most commonly prescribed medications include amphetamines (e.g., Adderall, a mix of amphetamine salts) and methylphenidate (e.g., Ritalin and Concertaa formulation that releases medication in the body over a period of time). These medications have a paradoxically calming and focusing effect on individuals with ADHD. Researchers speculate that because methylphenidate amplifies the release of dopamine, it can improve attention and focus in individuals who have dopamine signals that are weak.

One of the most controversial issues in child psychiatry is whether the use of stimulant medications to treat ADHD increases the risk of substance abuse in adulthood. Research thus far suggests that individuals with ADHD do not become addicted to their stimulant medications when taken in the form and dosage prescribed by their doctors. Furthermore, several studies report that stimulant therapy in childhood does not increase the risk for subsequent drug and alcohol abuse disorders later in life. More research is needed, however, particularly in adolescents treated with stimulant medications.

Prescription Stimulants Abuse

Stimulants have been abused for both performance enhancement and recreational purposes (i.e., to get high). For the former, they suppress appetite (to facilitate weight loss), increase wakefulness, and increase focus and attention. The euphoric effects of stimulants usually occur when they are crushed and then snorted or injected. Some abusers dissolve the tablets in water and inject the mixture. Complications from this method of use can arise because insoluble fillers in the tablets can block small blood vessels.

Adverse Effects on Health

Stimulants can increase blood pressure, heart rate, body temperature, and decrease sleep and appetite, which can lead to malnutrition and its consequences. Repeated use of stimulants can lead to feelings of hostility and paranoia. At high doses, they can lead to serious cardiovascular complications, including stroke. Addiction to stimulants is also a very real consideration for anyone taking them without medical supervision. This most likely occurs because stimulants, when taken in doses and routes other than those prescribed by a doctor, can induce a rapid rise in dopamine in the brain. Furthermore, if stimulants are used chronically, withdrawal symptoms including fatigue, depression, and disturbed sleep patterns can emerge when the drugs are discontinued.


How Widespread Is Prescription Stimulant Abuse

Monitoring the Future (MTF) survey assesses the extent of drug use among 8th-, 10th-, and 12th-graders nationwide. For amphetamines and methylphenidate, the survey measures only past-year use, which refers to use at least once during the year preceding an individuals response to the survey. Use outside of medical supervision was first measured in the study in 2001; nonmedical use of stimulants has been falling since then, with total declines between 25 percent and 42 percent at each grade level surveyed. MTF data for 2008 indicate past-year nonmedical use of Ritalin by 1.6 percent of 8th-graders, 2.9 percent of 10th-graders, and 3.4 percent of 12th-graders. Since its peak in the mid-1990s, annual prevalence of amphetamine use fell by one-half among 8th-graders to 4.5 percent and by nearly one-half among 10th-graders to 6.4 percent in 2008. Amphetamine use peaked somewhat later among 12th-graders and has fallen by more than one-third to 6.8 percent by 2008. Although general nonmedical use of prescription stimulants is declining in this group, when asked, What amphetamines have you taken during the last year without a doctors orders? 2.8 percent of all 12th-graders surveyed in 2007 reported they had used Adderall. Amphetamines rank third among 12th-graders for past-year illicit drug use.



Caffeine is a mild CNS stimulant and is found in coffee, tea, soft drinks, chocolate, kola nuts, certain medicines and over-the-counter products. It is most commonly consumed by drinking coffee, tea or soft drinks and is used to temporarily ward off drowsiness and to restore alertness. Caffeine is the world’s most widely consumed psychoactive substance, but, unlike many other psychoactive substances, is legal and unregulated in nearly all jurisdictions. Beverages containing caffeine are enjoying great popularity; in North America, over 80% adults consume caffeine daily. The U.S. Food and Drug Administration (FDA) list caffeine as a “multiple purpose generally recognized as safe food substance”. It has many effects on the body’s metabolism, including stimulating the central nervous system. This can make you more alert and give you a boost of energy.

For most people, the amount of caffeine in two to four cups of coffee a day is not harmful. However, too much caffeine can make you restless, anxious, and irritable. It may also keep you from sleeping well and cause headaches, abnormal heart rhythms, or other problems. If you stop using caffeine, you could get withdrawal symptoms (includes headaches, nausea, sleep disorder, fatigue, anxiety, irritability, and general restlessness).  The withdrawal symptoms will subside in one to three months.

Some people are more sensitive to the effects of caffeine than others. They should limit their use of caffeine. So should pregnant and nursing women. Certain drugs and supplements may interact with caffeine. If you have questions about whether caffeine is safe for you, talk with your health care provider.


Cigarettes and other forms of tobacco including cigars, pipe tobacco, snuff, and chewing tobacco contain the addictive drug nicotine. Nicotine is readily absorbed into the bloodstream when a tobacco product is chewed, inhaled, or smoked. A typical smoker will take 10 puffs on a cigarette over a period of 5 minutes that the cigarette is lit. Thus, a person who smokes about 1 1/2 pack daily gets 300 hits of nicotine each day. Upon entering the bloodstream, nicotine immediately stimulates the adrenal glands to release the hormone epinephrine (adrenaline). Epinephrine stimulates the central nervous system and increases blood pressure, respiration, heart rate and elevated blood sugar levels (nicotine suppresses insulin output from the pancreas).

Like cocaine and other stimulants, nicotine increases levels of the neurotransmitter dopamine, which affects the brain pathways that control reward and pleasure. Long time use of tobacco can result in addiction, a condition of compulsive drug seeking and use, even in the face of negative consequences. When an addicted user tries to quit, he or she experiences withdrawal symptoms including irritability, attention difficulties, sleep disturbances, increased appetite, and powerful cravings for tobacco. Treatments can help smokers manage these symptoms and improve the likelihood of successfully quitting.

Tobacco use is the leading preventable cause of disease, disability, and death in the United States. Between 1964 and 2004, smoking caused over 11 million deaths, including over 4 million cancer deaths, over 5 million deaths from cardiovascular diseases, over 1 million deaths from respiratory diseases, and approximately 100K infant deaths related to mothers smoking during pregnancy.


OTC and prescription medications are highly beneficial treatments for a variety of health conditions. Pain relievers enable individuals with chronic pain to lead productive lives; tranquilizers can reduce anxiety and help patients with sleep disorders; and stimulants help people with attention-deficit hyperactivity disorder (ADHD) focus their attention. Most people who take prescription medications use them responsibly. But when abused that is, taken by someone other than the patient for whom the medication was prescribed, or taken in a manner or dosage other than what was prescribed prescription medications can produce serious adverse health effects, including addiction.

Patients, health care professionals, and pharmacists all have roles in preventing the abuse1 of and addiction to prescription medications. For example, patients should follow the directions for use carefully; learn what effects and side effects the medication could have; and inform their doctor/pharmacist whether they are taking other medications [including over-the-counter (OTC) medications or health supplements], since these could potentially interact with the prescribed medication. The patient should read all information provided by the pharmacist. Physicians and other health care providers should screen for past or current substance abuse in the patient during routine examination, including asking questions about what other medications the patient is taking and why. Providers should note any rapid increases in the amount of a medication needed or frequent requests for refills before the quantity prescribed should have been finished, as these may be indicators of abuse.1

Similarly, some OTC medications, such as cough and cold medicines containing dextromethorphan, have beneficial effects when taken as recommended; but they can also be abused and lead to serious adverse health consequences. Parents should be aware of the potential for abuse of these medications, especially when consumed in large quantities, which should signal concern and the possible need for intervention.

Although many prescription medications can be abused, the following three classes are most commonly abused:

        Opioids usually prescribed to treat pain.

        CNS depressants used to treat anxiety and sleep disorders.

         Stimulants prescribed to treat ADHD and narcolepsy.

These medications are only safe to use with other substances under a physicians supervision. Typically, they should not be used with alcohol, antihistamines, barbiturates, or benzodiazepines. Because these other substances slow breathing, their effects in combination with opioids could lead to life-threatening respiratory depression.  Stimulants are the only classification addressed in this Continuing Education Course.

As mentioned previously, stimulants (amphetamines [Adderall, Dexedrine] and methylphenidate [Concerta, Ritalin]) increase alertness, attention, and energy. They also increase blood pressure and heart rate, constrict blood vessels, increase blood glucose, and open up the pathways of the respiratory system. Historically, stimulants were prescribed to treat asthma and other respiratory problems, obesity, neurological disorders, and a variety of other ailments. As their potential for abuse and addiction became apparent, the prescribing of stimulants by physicians began to wane. Now, stimulants are prescribed for treating only a few health conditions, most notably ADHD, narcolepsy, and, in some instances, depression that has not responded to other treatments.

Stimulants may be taken orally, but some abusers crush the tablets, dissolve them in water, and then inject the mixture; complications can arise from this because insoluble fillers in the tablets can block small blood vessels. Stimulants have been abused for both performance enhancement and recreational purposes (i.e., to get high).

Stimulants have chemical structures that are similar to key brain neurotransmitters called monoamines, including dopamine and norepinephrine. Their therapeutic effect is achieved by slow and steady increases of dopamine that are similar to the natural production of this chemical by the brain. The doses prescribed by physicians start low and increase gradually until a therapeutic effect is reached. However, when taken in doses and routes other than those prescribed, stimulants can increase the brains dopamine levels in a rapid and highly amplified manneras do most other drugs of abuse disrupting normal communication between brain cells, producing euphoria, and increasing the risk of addiction.

Taking high doses of a stimulant can result in an irregular heartbeat, dangerously high body temperatures, and/or the potential for cardiovascular failure or seizures. Taking some stimulants in high doses or repeatedly can lead to hostility or feelings of paranoia in some individuals.

Stimulants should not be mixed with antidepressants, which may enhance the effects of a stimulant; or with OTC cold medicines containing decongestants, which may cause blood pressure to become dangerously high or may lead to irregular heart rhythms.

Treatment of addiction to prescription stimulants is based on behavioral therapies proven effective for treating cocaine or methamphetamine addiction. At this time, there are no proven medications for the treatment of stimulant addiction. Depending on the patients situation, the first step in treating prescription stimulant addiction may be to decrease the drugs dose slowly and attempt to treat withdrawal symptoms (mood changes, sleep and appetite disturbances). This process of detoxification could then be followed with one of many behavioral therapies: contingency management, for example, improves treatment outcomes by enabling patients to earn vouchers for drug-free urine tests; the vouchers can be exchanged for items that promote healthy living. Cognitive-behavioral therapies which teach patients skills to recognize risky situations, avoid drug use, and cope more effectively with problems are proving beneficial. Recovery support groups may also be effective in conjunction with a behavioral therapy.

Dextromethorphan (DXM) is the active ingredient found in OTC cough and cold medications. When taken in recommended doses, these medications are safe and effective. DXM is taken orally. In order to experience the mind-altering effects of DXM, excessive amounts of liquid or gelcaps must be consumed. The availability and accessibility of these products make them a serious concern, particularly for youth, who tend to be their primary abusers. In very large quantities, DXM can cause effects similar to those of ketamine and PCP because these drugs affect similar sites in the brain. These effects can include impaired motor function, numbness, nausea/vomiting, and increased heart rate and blood pressure. On rare occasions, hypoxic brain damage caused by severe respiratory depression and a lack of oxygen to the brain has occurred due to the combination of DXM with decongestants often found in the medication.

Monitoring the Future (MTF) surveys assesses the extent of drug use among 8th-, 10th-, and 12th-graders nationwide. Nonmedical use of any prescription drug is reported only for 12th-graders, and in 2008, 15.4 percent reported past-year use. Prescription and OTC medications were the most commonly abused drugs by high school students after marijuana. In addition, they represent 6 of the top 10 illicit drugs reported by 12th-graders.

Qs and As (Note: Qs are general and they are not directed specifically at Stimulant drugs)

Q-1: How Do drugs Produce Euphoria?

Drugs change the way the brain works by changing the way nerve cells communicate. Nerve cells, called neurons, send messages to each other by releasing chemicals called neurotransmitters. Neurotransmitters work by attaching to key sites on neurons called receptors. Learn more about how neurotransmitters work in the section How Does Your Brain Communicate?

There are many neurotransmitters, but dopamine is one that is directly affected by most stimulants. Dopamine makes people feel good when they do something they enjoy, like eating a piece of chocolate cake or riding a roller coaster. Stimulants cause a buildup of dopamine in the brain, which can make people who abuse stimulants feel intense pleasure and increased energy. They can also make people feel anxious and paranoid. And with repeated use, stimulants can disrupt the functioning of the brains dopamine system, dampening users ability to feel any pleasure at all. Users may try to compensate by taking more and more of the drug to experience the same pleasure.

Q 2: What Are the Short-Term Effects?

In the short term, some drugs especially stimulants can produce joyful feelings, increase wakefulness, and decreases appetite. Users can become more talkative, energetic, or anxious and irritable. Other short-term effects of stimulants can include increased body temperature, heart rate, and blood pressure; dilated pupils; nausea; blurred vision; muscle spasms; and confusion.  Stimulants can also cause the bodys blood vessels to narrow, constricting the flow of blood, which forces the heart to work harder to pump blood through the body. The heart may work so hard that it temporarily loses its natural rhythm. This is called fibrillation and can be very dangerous because it stops the flow of blood through the body.

Q 3: What Are the Long-Term Effects?

As with many types of drugs, repeated abuse can cause addiction. That means that someone repeatedly seeks out and uses the drug despite its harmful effects. Repeated drug use changes the brain in ways that contribute to the drug craving and continued drug seeking and use that characterizes addiction. Other effects of long-term stimulant abuse can include paranoia, aggressiveness, extreme anorexia, thinking problems, visual and auditory hallucinations, delusions, and severe dental problems.

For example, repeated use of cocaine can lead to tolerance of its euphoric effects, causing the user to take higher doses or to use the drug more frequently (e.g., binge use) to get the same effects. Such use can lead to bizarre, erratic behavior. Some cocaine users experience panic attacks or episodes of full-blown paranoid psychosis, in which the individual loses touch with reality and hears sounds that aren’t there (auditory hallucinations). Different ways of using cocaine can produce different adverse effects. For example, regularly snorting cocaine can lead to hoarseness, loss of the sense of smell, nosebleeds, and a chronically runny nose. Cocaine taken orally can cause reduced blood flow, leading to bowel problems.

Repeated use of methamphetamine can cause violent behavior, mood disturbances, and psychosis, which can include paranoia, auditory hallucinations, and delusions (e.g., the sensation of insects creeping on the skin. The paranoia can result in homicidal and suicidal thoughts. Methamphetamine can increase a persons sex drive and is linked to risky sexual behaviors and the transmission of infectious diseases, such as HIV. However, research also indicates that long-term methamphetamine use may be associated with decreased sexual function, at least in men.

Q 4: Can These Drugs Be Lethal?

Yes, in rare instances, sudden death can occur on the first use of cocaine or unexpectedly thereafter. And, like most drugs, stimulants can be lethal when taken in large doses or mixed with other substances. Stimulant overdoses can lead to heart problems, strokes, hyperthermia (elevated body temperature), and convulsions, which if not treated immediately can result in death. Abuse of both cocaine and alcohol compounds the danger, increasing the risk of overdose.

Q 5: What Are the Differences Between Cocaine and Methamphetamine?

They act in different ways to increase dopamine in the brain. Cocaine works by blocking the dopamine transporter; that is, it doesn’t allow dopamine to be recycled back into the neuron after it has done its work. Methamphetamine interferes with this recycling process as well, but it also causes too much dopamine to be released. Another difference is that cocaine disappears from the brain quickly, while methamphetamine has a much longer duration of action. The longer presence in the brain ultimately makes methamphetamine more harmful to brain cells.

Q 6: If a Pregnant Woman Uses Stimulants, Will the Baby Be Hurt?

In the United States between 2006 and 2007, 22.6 percent (or 20,000) of teens ages 15 to 17 used an illicit drug during their pregnancy. Scientists have found that exposure to cocaine during fetal development may lead to subtle but significant deficits later in life, including problems with attention and information processing abilities that are important for success in school. Research is also underway on the effects of methamphetamine use during pregnancy. So far, the data suggest that it may affect fetal growth and contribute to poor quality of movement in infants.

Research in this area is particularly difficult to interpret because it is often hard to single out a drugs specific effects among the multiple factors that can all interact to affect maternal, fetal, and child outcomes. These factors include exposure to all drugs of abuse, including nicotine and alcohol; extent of prenatal care; possible neglect or abuse of the child; exposure to violence in the environment; socioeconomic conditions; maternal nutrition; other health conditions; and exposure to sexually transmitted diseases.

Q 7: What Treatments Are Available for Stimulant Abuse?

Several behavioral therapies are effective in treating addiction to stimulants. These approaches are designed to help the person think differently, change their expectations and behaviors, and increase their skills in coping with various stresses in life. One form that is showing positive results in people addicted to either cocaine or methamphetamine is called contingency management, or motivational incentives (MI). These programs reward patients who refrain from using drugs by offering vouchers or prizes. MI may be particularly useful for helping patients to initially stop taking the drug and for helping them to stay in treatment.

Currently, there are no medications approved by the U.S. Food and Drug Administration to treat people who are addicted to stimulants, although that is an active area of research for NIDA.

As with other drugs of abuse, it is possible for individuals to become dependent upon or addicted too many stimulants. Withdrawal symptoms associated with discontinuing stimulant use include fatigue, depression, and disturbance of sleep patterns. Repeated use of some stimulants over a short period can lead to feelings of hostility or paranoia. Further, taking high doses of a stimulant may result in dangerously high body temperature and an irregular heartbeat. There is also the potential for cardiovascular failure or lethal seizures.

Stimulants should be used in combination with other medications only under a physician’s supervision. Patients also should be aware of the dangers associated with mixing stimulants and OTC cold medicines that contain decongestants; combining these substances may cause blood pressure to become dangerously high or lead to irregular heart rhythms.

Q 8: How does the brain communicate?

The brain is a communications center consisting of billions of neurons, or nerve cells. Networks of neurons pass messages back and forth to different structures within the brain, the spinal column, and the peripheral nervous system. These nerve networks coordinate and regulate everything we feel, think, and do.  The brain communicates via:

Neuron to Neuron: Each nerve cell in the brain sends and receives messages in the form of electrical impulses. Once a cell receives and processes a message, it sends it on to other neurons.

Neurotransmitters:  The messages are carried between neurons by chemicals called neurotransmitters.

Receptors: The neurotransmitter attaches to a specialized site on the receiving cell called a receptor. A neurotransmitter and its receptor operate like a “key and lock,” an exquisitely specific mechanism that ensures that each receptor will forward the appropriate message only after interacting with the right kind of neurotransmitter.

Transporters: Located on the cell that releases the neurotransmitter, transporters recycle these neurotransmitters (i.e., bringing them back into the cell that released them), thereby shutting off the signal between neurons.

To send a message a brain cell releases a chemical (neurotransmitter) into the space separating two cells called the synapse. The neurotransmitter crosses the synapse and attaches to proteins (receptors) on the receiving brain cell. This causes changes in the receiving brain cell and the message is delivered.  

Q 9: How do drugs work in the brain?

Drugs are chemicals. They work in the brain by tapping into the brain’s communication system and interfering with the way nerve cells normally send, receive, and process information. Some drugs, such as marijuana and heroin, can activate neurons because their chemical structure mimics that of a natural neurotransmitter. This similarity in structure “fools” receptors and allows the drugs to lock onto and activate the nerve cells. Although these drugs mimic brain chemicals, they don’t activate nerve cells in the same way as a natural neurotransmitter, and they lead to abnormal messages being transmitted through the network.

Other drugs, such as amphetamine or cocaine, can cause the nerve cells to release abnormally large amounts of natural neurotransmitters or prevent the normal recycling of these brain chemicals. This disruption produces a greatly amplified message, ultimately disrupting communication channels. The difference in effect can be described as the difference between someone whispering into your ear and someone shouting into a microphone.

Q 10: How do drugs work in the brain to produce pleasure?

All drugs of abuse directly or indirectly target the brain’s reward system by flooding the circuit with dopamine. Dopamine is a neurotransmitter present in regions of the brain that regulate movement, emotion, cognition, motivation, and feelings of pleasure. The overstimulation of this system, which rewards our natural behaviors, produces the euphoric effects sought by people who abuse drugs and teaches them to repeat the behavior.

Q 11: How does stimulation of the brain’s pleasure circuit teach us to keep taking drugs?

Our brains are wired to ensure that we will repeat life-sustaining activities by associating those activities with pleasure or reward. Whenever this reward circuit is activated, the brain notes that something important is happening that needs to be remembered, and teaches us to do it again and again, without thinking about it. Because drugs of abuse stimulate the same circuit, we learn to abuse drugs in the same way.

Q 12: Why are drugs more addictive than natural rewards?

When some drugs of abuse are taken, they can release 2 to 10 times the amount of dopamine that natural rewards do. In some cases, this occurs almost immediately (as when drugs are smoked or injected), and the effects can last much longer than those produced by natural rewards. The resulting effects on the brain’s pleasure circuit dwarfs those produced by naturally rewarding behaviors such as eating and sex.16,17 The effect of such a powerful reward strongly motivates people to take drugs again and again. This is why scientists sometimes say that drug abuse is something we learn to do very, very well. 

Q 13: What happens to your brain if you keep taking drugs?

Just as we turn down the volume on a radio that is too loud, the brain adjusts to the overwhelming surges in dopamine (and other neurotransmitters) by producing less dopamine or by reducing the number of receptors that can receive and transmit signals. As a result, dopamine becomes abnormally low, and the ability to experience any pleasure is reduced. This is why the abuser eventually feels flat, lifeless, and depressed, and is unable to enjoy things that previously brought them pleasure. Now, they need to take drugs just to bring their dopamine function back up to normal. And, they must take larger amounts of the drug than they first did to create the dopamine high – an effect known as tolerance.

Q 14: How does long-term drug taking affect brain circuits?

We know that the same sort of mechanisms involved in the development of tolerance can eventually lead to profound changes in neurons and brain circuits, with the potential to severely compromise the long-term health of the brain. For example, glutamate is another neurotransmitter that influences the reward circuit and the ability to learn. When the optimal concentration of glutamate is altered by drug abuse, the brain attempts to compensate for this change, which can cause impairment in cognitive function. Similarly, long-term drug abuse can trigger adaptations in habit or non-conscious memory systems. Conditioning is one example of this type of learning, whereby environmental cues become associated with the drug experience and can trigger uncontrollable cravings if the individual is later exposed to these cues, even without the drug itself being available. This learned “reflex” is extremely robust and can emerge even after many years of abstinence.

Q 15:  What other brain changes occur with abuse?

Chronic exposure to drugs of abuse disrupts the way critical brain structures interact to control behavior – behavior specifically related to drug abuse. Just as continued abuse may lead to tolerance or the need for higher drug dosages to produce an effect, it may also lead to addiction, which can drive an abuser to seek out and take drugs compulsively. Drug addiction erodes a person’s self-control and ability to make sound decisions, while sending intense impulses to take drugs.


Various web sites; specifically the NIDA web site