Stimulant
drugs excite the central nervous system, increasing alertness, decreasing fatigue, and delaying sleep. Some also impair appetite and may be prescribed to promote weight loss. Most users of these drugs experience a sense of well-being (euphoria), but this reaction depends greatly on the drug taken and the dose. Signs of overstimulation by these drugs, such as muscle tremors or irregular heart rate, are common.
Almost all societies have discovered some indigenous plant that produces
Stimulant effects. Coca leaves, for instance, are chewed by South American Indians and are the source of the drug cocaine; khat leaves, whose active ingredient is norpseudoephedrine, are chewed by Middle Eastern peoples; betel nuts, containing arecoline, are chewed by Asians and South Pacific Islanders.
cocaine and
caffeine are the most familiar natural stimulants, and the amphetamines the best-known synthetic ones. Other drugs that have been used as emergency
stimulants include strychnine, pentylenetetrazol, and ammonia.
Caffeine
The beverages coffee, tea, cocoa, and many soft drinks contain caffeine, the most widely used stimulant drug in the world. Cola drinks derive their caffeine content (50-75 mg per can) from the kola nut. A moderately strong cup of coffee may contain about 75 to 125 mg of caffeine, a dose that is just above the threshold for recognition in most persons. People differ greatly in their susceptibility to the stimulant effects of this drug, a difference thought to be based on genetic factors. Even over the course of an individual's lifetime, the response to caffeine may change: the effects become more pronounced with increasing age. Heavy users often become nervous, irritable, apprehensive, restless, and unable to sleep; such symptoms may be construed as a psychiatric disorder unless the history of caffeine misuse is known. Recognition of the drug effects of these beverages has led to the increased use of decaffeinated coffee, tea, and colas.
Cocaine
Sigmund Freud was among the first to describe the effect of cocaine, an alkaloid drug, on the central nervous system. He confirmed the euphoric effects and the increased energy and alertness noted by coca leaf chewers for centuries. Once cocaine was isolated (1855), it came into medical use as a local anesthetic and as a nasal decongestant, because it shrinks mucous membranes. Its role in medicine has declined, but it has since become a major drug of abuse.
The usual extraction of cocaine from coca paste results in the acidic cocaine hydrochloride. When neutralized by alkali, crystals of the pure alkaloid, cocaine, are formed. This form, known as "free-base" or more commonly "crack," can be smoked. When used this way, the drug enters the circulation promptly, reaching the brain in seconds. Such rapidity of reward accounts for the highly addicting potential of crack. Absorption of the hydrochloride through the mucous membrane of the nose (sniffing) is slower. Intravenous use is considered too dangerous by most users. No matter how taken, cocaine produces a short-term sense of intense euphoria and alertness, which accounts for its widespread abuse.
Immediate complications of cocaine use include strokes or myocardial infarcts (due to the vasoconstrictive action) and seizures or ventricular arrhythmias (due to local anesthetic action). Long-term complications may include a paranoid state and declining cognition.
Amphetamines
Amphetamines, widely used in medical practice until recently, are sympathomimetic stimulants, acting physiologically in ways similar to the sympathetic nervous system. Although synthetic, they are chemically related to ephedrineÑa mild stimulant derived from Chinese shrubs of the genus EphedraÑwhich is used to alleviate respiratory ailments.
Amphetamine (phenylisopropylamine) was first introduced into medical practice in the 1930s. It was widely used as an appetite suppressant, as a treatment for narcolepsy (uncontrollable attacks of slepiness), and as a treatment for hyperactivity. It was also inhaled as a nasal decongestant. Other drugs with similar actions were also synthesized, including methamphetamine, methylphenidate, and pipradol.
abuse of these stimulants remained a relatively minor problem in the United States until the enormous upsurge of drug abuse in the 1960s. The drug methamphetamine, for example, known in street terminology as "speed," became a favored drug of abuse because it could be manufactured more easily by illicit means than other, related drugs. Crystals of
methamphetamine ("crystal" ) were usually dissolved and injected intravenously. This form of the drug can also be smoked and has enjoyed a new popularity in the form of "ice." The effects are not only as intense as those of crack, but much longer lasting.
Other amphetamine-related drugs used for weight loss include diethylproprion, chlorphentermine, and phenmetrazine. All amphetaminelike drugs have abuse potential, although abuse cannot be sustained because of the drugs' effects on sleep and appetite. When forced to stop, a user has withdrawal symptoms such as excessive sleepiness, ravenous appetite, and mental depression. Long-term psychological changes may follow.
Some methamphetamine homologues such as 3, 4-methylenedioxy methamphetamine, have been abused under the names of "Ecstasy," "Adam," and "Eve." Although they can cause mild hallucinations, they seem largely to be stimulants.
More abstracts about the STIMULANTS