Stimulants are a type of drug that alters activity within the central and peripheral nervous systems. Most stimulants have an effect on blood pressure, heart rate, and alertness. Some drugs within this category have immense therapeutic value, while some have no clinical application.

Types of Stimulants

Central nervous system stimulants can be divided into three groups:

  1. Convulsants and Respiratory Stimulants: Bicuculline, Picrotoxin, Pentylenetetrazol, and Doxapram are the drugs of this group. These drugs have no clinical application and are often used in poisons, in intensive care settings, and for research. Their mechanism of action is unknown.
  2. Psychotomimetic Drugs/ Hallucinogens: These drugs produce hallucinations by altering the perception of the surrounding environment. Drugs in this group include lysergic acid, psilocybin, and mescaline.
  3. Psychomotor Stimulants: These psychotropic medications stimulate the central nervous system (CNS) by boosting the release of certain chemicals in the brain. They include:
    1. Adderall (amphetamine and dextroamphetamine)
    2. Dexedrine (dextroamphetamine)
    3. Ritalin (methylphenidate)

Other stimulant drugs include cocaine, methylxanthines (theophylline and caffeine), nicotine, and vareniciline.

It should be noted that nearly all psychotropic prescription medications produce better results for people in treatment if they are paired with a type of psychotherapy. Psychotherapy can help a person address the emotions, triggers, and behaviors associated with mental health conditions, in addition to helping them develop positive coping strategies that can dramatically improve a person’s quality of life.

Mechanism of Action

These drugs achieve their beneficial effects by increasing the levels of dopamine, serotonin, and norepinephrine in the brain. Dopamine, one of the most important neurotransmitters, is related to concentration, attention, and feelings of reward and pleasure. Norepinephrine plays an important role in alertness. Some stimulant drugs also increase the level of glutamate, a neurotransmitter associated with behavioral control and inhibition. People experiencing attention deficit hyperactivity (ADHD) often have low levels of glutamate.

Methyxanthines inhibit the phosphodiesterase enzymes. This increases intracellular cyclic adenosine monophosphate. Moreover, they also block adenosine receptors and increase the movement of extracellular calcium. Nicotine, at high doses, produces ganglionic stimulation. It binds with all nicotinic receptors. Varenicline has a similar action to nicotine.
 

Amphetamine exerts effects by promoting the release of monoamines (serotonin, dopamine, and norepinephrine). Amphetamine may also inhibit the function of monoamine oxidase. Cocaine inhibits the activity of transporters that promote the reuptake of monoamines.

Therapeutic Uses

There are a variety of reasons a person may be prescribed a stimulant by their doctor, such as:

  • ADHD: In both children and adults, ADHD is the most common reason for a stimulant prescription. By one estimate, 8% of children experience ADHD, while 2% to 5% of adults are diagnosed. While it may seem odd to prescribe a stimulant drug to someone with hyperactivity, these drugs actually increase a person's ability to control their urges and behaviors. Overall, the effect is calming and leads to improved focus in school and at work.

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  • Narcolepsy: Stimulant drugs are also prescribed for the treatment of narcolepsy. People with narcolepsy have sudden attacks of extreme sleepiness, impairing basic functioning and preventing them from doing simple tasks such as driving or working a regular job. Stimulants help the person maintain alertness throughout the day.
  • Exogenous Obesity: Amphetamines are used for exogenous obesity (obesity from consuming too many calories).
  • Headache: Caffeine is sometime used to treat headaches. It may used in combination with various analgesics to relieve pain, stress, tension, and fatigue.

Side Effects

People taking stimulants should monitor their health for potential side effects. Unintended side effects can impact various parts of a person's health and functioning, such as:

  • Cardiovascular System: Amphetamines have several undesirable effects on the cardiovascular system. Hypertension is very common. Valculopathy (a disorder of the heart valves), syncope, arrhythmias, hypertension, angina pain, and circulator collapse are all possible side effects. Chills, sweating, and headache may occur as well. Cardiomyopathy and myocardial infarction with sudden death, although rare, are dangerous side effects that have been reported with large doses.
  • Central Nervous System: Amphetamines may cause insomnia, weakness, dizziness, tremors, hyperactive reflex, and confusion. The risk of suicidal thoughts, depression, and anxiety occur rarely at therapeutic doses. Seizure and coma are sometimes seen with high doses of amphetamines.
  • Pregnancy and Lactation: Amphetamines produce severe teratogenic effects (birth or developmental effects). Their metabolites are distributed in breast milk. Their use is contraindicated during pregnancy and lactation.
  • Other Effects: Nausea, vomiting, abdominal cramps, constipation, and diarrhea are other potential effects. Anorexia is also very common. Blurred vision, glaucoma, rashes, urticaria, and hypersensitivity may occur as well. 

Drug Interactions

It is important to disclose any other drugs or medications that you ingest with your doctor before taking a stimulant, as adverse drug interactions can occur. Certain substances may lose their effectiveness or negatively interact if taken with stimulants:

  • Antidepressants should be avoided since their use with psychomotor stimulants produces exaggerated cardiovascular effects.
  • Anticoagulants interfere with the metabolism of psychomotor stimulants.
  • Amphetamines increase the effects of the neurotransmitter norepinephrine, which aids in the body’s stress response.
  • Phenothiazine (chlorpromazine), an antipsychotic, counteracts the effects of psychomotor stimulants.
  • Amphetamines may antagonize the outcomes of antihypertensives (blood pressure medication).
  • Amphetamines may decrease the rate absorption of phenytoin (an anticonvulsant).
  • Insulin requirements may decrease while using amphetamines.

Dependency, Tolerance, and Withdrawal

Doctors will typically start a person on a low dose of stimulant drugs, gradually working up to a dosage that is a good balance between effectiveness and adverse effects. Dependency can become an issue with stimulants such as amphetamines. Amphetamine psychosis, a condition that can present like schizophrenia, may occur if a person is receiving an incorrect dose or abusing stimulants. A high euphoric state exists in this condition and it is possible for the person experiencing it to become violent. Tolerance to stimulants will increase gradually as time passes.

Recently, nonstimulant alternatives to Ritalin and Adderall have made inroads in the treatment of ADHD. Strattera (atomoxetine) is an example of the next generation of ADHD medications. There are many advantages to a nonstimulant treatment solution such as less potential for abuse or addiction. Nonprescription use of drugs like Adderall and Dexedrine presents a serious problem, especially in academic and other performance-oriented environments. In addition, nonstimulant medications typically have fewer side effects than their stimulant counterparts.

If a person discontinues a stimulant drug, the body must make up for the neurotransmitters that were produced while in treatment. Without these neurotransmitters, a person may feel exhausted or sick and his or her mood will likely be affected. He or she may also have trouble sleeping. In general, dosages are tapered off between you and your doctor in order to avoid unpleasant withdrawal symptoms and to readjust your body to function without the drug.

References:

  1. American Academy of Pediatrics: Subcommittee on Attention Deficit/Hyperactivity Disorder and Committee on Quality Improvement. (2001). Clinical Practice Guideline: Treatment of the School-Aged Child with Attention-Deficit/Hyperactivity Disorder. Pediatrics, 108, 1033–1044.
  2. Fredholm, B. B., Battig, K., Holmes, J. et al. (1999). Actions of Caffeine in the Brain with Special Reference to Factors that Contribute to its Widespread Use. Pharmacol Rev, 51, 83–133. (Comprehensive review article covering pharmacological, behavioral, and social aspects)
  3. National Institute on Drug Abuse. (n.d.). InfoFacts: Stimulant ADHD Medications — Methylphenidate and Amphetamines. Retrieved from http://www.drugabuse.gov/publications/infofacts/stimulant-adhd-medications-methylphenidate-amphetamines
  4. National Institute of Mental Health. (n.d.). Mental Health Medications. Retrieved from http://www.nimh.nih.gov/health/publications/mental-health-medications/complete-index.shtml#pub8
  5. Voeller, K.K.S. (2004). Attention-Deficit Hyperactivity Disorder (ADHD). J Child Neurol, 19, 798–814.