Cocaine and Amphetamines

Cocaine is derived from the coca plant, native to South America, and is typically insufflated nasally ("snorted"), smoked (in the form of "freebase" or "crack"), or injected intravenously. Amphetamines are analogues of naturally occurring ephedrine and have been abused in various forms since their original synthesis in 1887. Currently, ¿-methamphetamine ("crystal meth," "meth") is the most popular form of amphetamine abused, and in some areas of the country, such as the West Coast, abuse of meth-amphetamine is more prevalent than cocaine abuse. Cocaine acts as a competitive blocker of dopamine reuptake in the synaptic cleft, which increases the concentration in the cleft, with resultant activation of dopamine type 1 and 2 receptors. In addition, cocaine increases norepinephrine and serotonin neurotransmission via reuptake inhibition, but these monoamines do not play the dominant role in its CNS effects (Jaffe 1999b). By contrast, amphetamine increases the availability of all synaptic monoamines by stimulating the release of catecholamines, particularly dopamine, from the presynaptic terminals. This effect is especially potent for dopaminergic neurons projecting from the ventral tegmental area to the cerebral cortex and limbic areas, known as the "reward pathway."

Patients with schizophrenia who abuse stimulants experience significant increases in the extent of positive symptoms of their psychosis. In comparison to schizophrenia patients, cocaine-abusing patients without underlying psychotic disorders tend to seek treatment more often for depression and anxiety than for psychosis (Serper et al. 1999). Withdrawal following heavy stimulant use may be associated with significant lethargy and depression and an increased risk for suicide (Gawin and Kleber 1986).

Cocaine and amphetamines have similar health effects based on their similar pharmacological activities that result in increased synaptic dopa-mine and other monoamines. The resultant sympathomimetic and vaso-constrictive properties of these agents are responsible for many of the acute (e.g., myocardial infarction, cardiac arrhythmias, cerebrovascular accidents, seizures) and chronic (e.g., hypertension) effects of ingestion (Jaffe

1999a). The nasal route of administration can lead to general sinus congestion and septal perforation due to chronic ischemia. The intravenous route of administration not only increases the transmission risk of HIV and hepatitis B and C viruses, but intravenous and subcutaneous ("skin popping") use may also result in significant cellulitis, bone and joint infections, endocarditis, and renal failure (usually as a result of adulterants to the drug). Smoking cocaine can exacerbate preexisting asthma or chronic obstructive pulmonary disease, and can produce specific, fibrotic lung changes known as "crack lung" (Tashkin 2001). Chronic use of stimulants often results in significant weight loss due to the anorexic effects of these agents.

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