stimulante

Stimulante, in pharmacology, describes a class of substances that increase activity in the central nervous system and often in the autonomic nervous system. Typical effects include heightened alertness, improved attention and wakefulness, increased energy, faster speech, and, in many cases, reduced appetite. On a neurochemical level, stimulants often raise extracellular levels of monoamines such as dopamine and norepinephrine; exact mechanisms vary and can include promoting transmitter release, blocking reuptake, or inhibiting metabolism. Caffeine, the most widely consumed stimulant, mainly acts as an adenosine receptor antagonist; other stimulants such as amphetamine-like drugs promote dopamine and norepinephrine release; methylphenidate blocks reuptake; modafinil has a distinct but wakefulness-promoting action.

Common examples range from caffeine and nicotine to prescription medicines such as methylphenidate, dextroamphetamine, lisdexamfetamine, and modafinil, as well as illicit drugs like cocaine and methamphetamine. Medically, stimulants are used to treat ADHD and narcolepsy; they may also be prescribed for obesity under specific guidelines or for fatigue associated with certain disorders. Some stimulants have off-label or nonmedical uses, including cognitive enhancement, though such use carries risk and is often discouraged.

Regulatory status varies by country. Caffeine and nicotine are legal and widely available; many other stimulants are controlled substances requiring prescription or are illegal to possess. Potential adverse effects include insomnia, anxiety, increased heart rate and blood pressure, and decreased appetite. There is a risk of dependence and withdrawal upon cessation. Overuse or high doses can lead to cardiovascular complications, mood disturbances, and, in some cases, stimulant-induced psychosis or arrhythmias.