Amphetamines are a class of stimulant drugs that includes both prescription medications and illegal substances. The most commonly prescribed amphetamines are Adderall, Dexedrine, and Vyvanse, all used primarily to treat ADHD. Methamphetamine, MDMA (ecstasy), and synthetic cathinones (“bath salts”) also belong to the broader amphetamine family, though they differ significantly in their effects and legal status.
Prescription Amphetamines
Several FDA-approved medications are built on the amphetamine molecule. They are all classified as Schedule II controlled substances, meaning they have recognized medical uses but carry a high potential for abuse. Prescriptions for these drugs cannot be refilled and require a new prescription each time.
The most widely prescribed amphetamine medications include:
- Adderall and Adderall XR: A combination of four amphetamine salts, mixing both dextroamphetamine and levoamphetamine. Available in immediate-release and extended-release formulations. The recommended starting dose for adults with ADHD is 20 mg per day.
- Dexedrine (dextroamphetamine): Contains only the dextro form of amphetamine, which is the more potent isomer for stimulant effects.
- Vyvanse (lisdexamfetamine): A prodrug, meaning it’s therapeutically inactive when swallowed. Red blood cells in your body break it down into active dextroamphetamine over time, which creates a smoother, more consistent effect than traditional extended-release formulations that rely on slow tablet dissolution.
- Desoxyn (methamphetamine hydrochloride): A prescription form of methamphetamine approved for treating ADHD in children 6 and older. Rarely prescribed but still legally available.
These medications are prescribed primarily for ADHD and, in some cases, narcolepsy. They work by flooding the gaps between brain cells with dopamine and norepinephrine, two chemical messengers that regulate attention, motivation, and alertness. Amphetamines do this in multiple ways at once: they push these chemicals out of storage inside nerve cells, slow down their breakdown, and block the recycling process that normally clears them away.
Dextroamphetamine vs. Levoamphetamine
Amphetamine exists as two mirror-image molecules, called the dextro (d) and levo (l) isomers. This distinction matters because the two forms hit the brain differently. Dextroamphetamine is roughly three to five times more potent as a stimulant than levoamphetamine. The reason comes down to dopamine: the d-isomer is about four times more powerful at releasing dopamine, the chemical most responsible for amphetamine’s stimulant and mood-elevating effects.
Levoamphetamine, on the other hand, is roughly equal to dextroamphetamine at releasing norepinephrine, which influences alertness and physical energy. This gives it a more balanced profile. Adderall uses a 3:1 ratio of dextro to levo amphetamine, blending the stronger dopamine effects of the d-isomer with the norepinephrine activity of the l-isomer. Dexedrine and Vyvanse contain only the d-isomer.
Illegal and Recreational Amphetamines
The amphetamine molecule serves as the chemical backbone for a range of illicit drugs. These substances share the same core structure but have been modified in ways that dramatically change their effects, potency, and danger.
Methamphetamine is the most well-known illegal amphetamine. While a prescription form exists (Desoxyn), street methamphetamine is manufactured in unregulated labs and used at far higher doses. The addition of a methyl group to the basic amphetamine structure makes it cross into the brain more rapidly, producing a more intense and longer-lasting high.
MDMA (ecstasy or molly) is a chemical analog of amphetamine with an extra structural modification that shifts its effects toward serotonin release. This is what produces the feelings of emotional warmth and empathy that distinguish MDMA from traditional stimulant amphetamines. It still acts on dopamine and norepinephrine, but its serotonin effects dominate the experience.
Synthetic cathinones, often marketed as “bath salts,” are also part of the extended amphetamine family. They share the same core chemical framework (called the phenethylamine pharmacophore) as amphetamine and MDMA but have a carbonyl group added at one position. Despite the seemingly small structural change, these modifications can profoundly alter which brain chemicals are affected and how strongly, making their effects unpredictable and their abuse potential high.
How Amphetamines Affect the Body
At prescribed doses, amphetamines typically cause appetite suppression, increased heart rate, elevated blood pressure, and difficulty sleeping. Irritability and mood changes are also common. These effects are generally manageable under medical supervision and tend to stabilize over time.
At higher doses or with chronic misuse, the picture changes significantly. A study of 230 patients hospitalized for acute amphetamine abuse found an average heart rate of about 109 beats per minute (normal resting rate is 60 to 100). Sinus tachycardia, a persistently fast heart rhythm, appeared in 43% of those patients. Another 34% showed both a fast heart rate and a prolonged QT interval, an electrical pattern that raises the risk of dangerous heart rhythms. More serious complications included arrhythmias, dangerously high blood pressure, overheating, and in rare cases, heart attack or brain hemorrhage.
Long-term misuse can lead to psychological dependence, depression, aggressive behavior, and problems with memory and mood. These effects are dose-dependent and far more common with illicit use than with prescribed therapeutic doses.
Why Prodrug Formulations Exist
Vyvanse was specifically designed to reduce abuse potential. Because the drug is inactive until red blood cells chemically split it into active dextroamphetamine, crushing or injecting it doesn’t produce a faster or more intense high the way it would with traditional amphetamine tablets. The conversion process also creates a more predictable blood level of the active drug, with less variation from person to person and from dose to dose. This makes the therapeutic effect more consistent throughout the day compared to extended-release capsules that depend on slow physical dissolution in the gut.