An amphetamine is a central nervous system stimulant that works by flooding the brain with chemical messengers responsible for focus, alertness, and motivation. It is one of the most widely prescribed stimulant medications in the world, used primarily to treat ADHD and narcolepsy, and it is classified as a Schedule II controlled substance by the DEA due to its high potential for abuse.
How Amphetamines Work in the Brain
Your brain cells communicate by releasing tiny chemical signals called neurotransmitters into the gaps between them. Amphetamine primarily increases levels of two of these signals: dopamine, which drives feelings of reward and motivation, and norepinephrine, which sharpens alertness and attention. It also raises serotonin levels to a lesser degree.
What makes amphetamine unusual is that it doesn’t just block these chemicals from being recycled back into the cell the way many other drugs do. It actually enters the nerve cell, forces stored neurotransmitters out of their holding compartments, and then reverses the cell’s recycling pumps so they push dopamine and norepinephrine outward into the gap between cells instead of pulling them back in. At the same time, it slows the breakdown of these chemicals inside the cell. The net effect is a dramatic increase in the amount of dopamine and norepinephrine available to activate neighboring brain cells.
This surge in signaling is why amphetamines produce their characteristic effects: improved concentration, increased energy, reduced impulsivity, and, at higher doses, euphoria.
Medical Uses
Amphetamine was first synthesized in 1927 by the chemist G. A. Alles, who was looking for a cheaper alternative to ephedrine. By 1935, the pharmaceutical company Smith, Kline and French had introduced it as Benzedrine for treating narcolepsy and mild depression. Today, its approved uses have narrowed to two main conditions.
ADHD: Amphetamine-based medications are a first-line treatment for attention-deficit/hyperactivity disorder in children, adolescents, and adults. In people with ADHD, the boost in dopamine and norepinephrine helps compensate for underactivity in the brain’s attention and impulse-control circuits. The most well-known brand is Adderall, which contains a mix of amphetamine salts.
Narcolepsy: For people who experience excessive daytime sleepiness or sudden sleep attacks, amphetamines promote wakefulness. This was actually the original medical use dating back to the 1930s.
Immediate-Release vs. Extended-Release
Prescription amphetamines come in two main forms. Immediate-release tablets reach peak levels in the blood in about 3 hours and last 4 to 6 hours, so they’re typically taken two or three times a day. Extended-release capsules peak around 7 hours and last 8 to 12 hours, allowing a single morning dose to cover most of the day. For adults with ADHD, extended-release prescriptions usually start at 20 mg once daily, with a ceiling of about 60 mg per day. Immediate-release tablets start lower, at 5 mg once or twice daily, and are adjusted upward gradually.
Common Side Effects
Because amphetamines activate the body’s “fight or flight” nervous system, they cause the heart to beat faster and with more force. This raises blood pressure, which is the most common cardiovascular effect. Many people also experience decreased appetite, dry mouth, and difficulty sleeping, especially if a dose is taken too late in the day.
Research from Harvard Health suggests stimulants may cause a short-term spike in the risk of heart attacks, strokes, and abnormal heart rhythms. For most healthy people at therapeutic doses, these risks are small, but they become significant for anyone with pre-existing heart conditions. Psychological side effects can include anxiety, irritability, and restlessness.
Who Should Not Take Amphetamines
The FDA label lists several conditions that rule out amphetamine use entirely:
- Heart disease or moderate to severe high blood pressure, because the drug’s cardiovascular stimulation can worsen these conditions
- Overactive thyroid, which already puts the body in a stimulated state
- Glaucoma, since amphetamines can increase eye pressure
- History of drug abuse, given the medication’s potential for dependence
- Use of MAOI antidepressants within the past 14 days, because MAOIs slow the breakdown of amphetamine in the body, potentially causing a dangerous spike in blood pressure, severe headaches, or in rare cases, fatal reactions
Risks of Chronic Misuse
At prescribed doses for a diagnosed condition, amphetamines have a well-established safety profile. The picture changes significantly with chronic misuse or abuse. Over time, excessive use can lead to psychological dependence, meaning the person feels unable to function normally without the drug. Other consequences of long-term misuse include loss of appetite leading to malnutrition, depression, aggressive behavior, memory problems, mood instability, and disrupted sleep.
The cardiovascular toll is particularly serious. Chronic overstimulation of the sympathetic nervous system can lead to sustained high blood pressure, dangerous heart rhythms, heart muscle damage that may be irreversible, and in extreme cases, stroke or heart attack. Hyperthermia, a dangerous rise in body temperature, is another risk during acute overdose.
Amphetamine vs. Methamphetamine
Methamphetamine is a close chemical relative of amphetamine with one key difference: an extra methyl group attached to its structure. This small change makes methamphetamine more fat-soluble, which means it crosses from the bloodstream into the brain more easily and more rapidly. The result is a faster, more intense effect on dopamine release. Prescription methamphetamine does exist for limited medical uses, but the illicit form is far more commonly encountered and carries substantially higher risks of addiction and neurotoxicity than pharmaceutical amphetamine.
Legal Status
Amphetamine is classified as a Schedule II controlled substance in the United States, the same category as oxycodone, fentanyl, and cocaine. This means it has recognized medical value but carries a high potential for abuse and severe dependence. Prescriptions cannot be called in by phone in most states, require a new written prescription for each refill, and are tracked through prescription drug monitoring programs.