Agents of Abuse: Cocaine and Marijuana PDF

Agents of Abuse: Cocaine and Marijuana Shamonia Francis Drug Abuse Drug abuse is the use of illegal drugs or the use of prescription or over the counter drugs for purposes other than those for which they are meant to be used, or in excessive amounts. Drug abuse may lead to social, physical, emotiona...

Agents of Abuse: Cocaine and Marijuana Shamonia Francis Drug Abuse Drug abuse is the use of illegal drugs or the use of prescription or over the counter drugs for purposes other than those for which they are meant to be used, or in excessive amounts. Drug abuse may lead to social, physical, emotional, and job-related problems. Drug addiction is a non-medical term that refers to a drug abuser’s overwhelming preoccupation with the procurement and use of a drug. Drug Abuse Drugs of abuse usually act on the CNS to modify the user’s mental state, although some are used to enhance physical performance. Long-term use may lead to development of tolerance and to the development of psychologic or physical dependence or both. Complications related to parenteral drug administration under unsterile conditions are extremely common. Drug Abuse Classes of drugs which are frequently abused include: CNS Depressants Ethanol Barbiturates CNS Stimulants Cocaine Amphetamines Marijuana Drug Abuse Ø Drugs that act as CNS stimulants or depressants enhance the release of corresponding neurotransmitters. Ø Neurotransmitters are chemical mediators which facilitate communication between cells. Ø They can be either “Excitatory” or “Inhibitory” Drug Abuse Excitatory neurotransmitters Glutamate Nor-epinephrine Catecholamines Dopamine Serotonin (5HT) Inhibitory neurotransmitters GABA Glycine COCAINE Cocaine An inhibitor of the CNS transporters of dopamine, norepinephrine and serotonin. Circulating catecholamine concentrations can be elevated as much as 5-fold in cocaine users. Available in the form of “crack” which can be smoked. Cocaine Mechanism of Action Cocaine blocks the dopamine transporter (also norepinephrine and serotonin transporters at higher doses) in the CNS to inhibit uptake of dopamine into nerve terminals in the mesolimbic pathway that includes the ‘‘brain reward’’ centre. This leads to an elevation of mood (euphoria), agitation, increased heart rate and blood pressure, increased self-confidence and mental alertness. Cocaine Overdose Commonly result in fatalities from arrhythmias, seizures, or respiratory depression. Cardiac toxicity is partly due to blockade of norepinephrine reuptake by cocaine; its local anesthetic action contributes to the production of seizures. In addition, the powerful vasoconstrictive action of cocaine may lead to severe hypertensive episodes, resulting in myocardial infarcts and strokes Cocaine Withdrawal With the withdrawal of cocaine there is; Severe depression of mood is common and strongly reinforces the compulsion to use the drug. Apathy, irritability, increased sleep time, disorientation, depression Cocaine Pharmacologic Properties Cocaine is inhaled (snorted) or smoked (free-base form, ‘‘crack cocaine’’) Short-term, repeated IV administration or smoking (referred to as a ‘‘spree’’ or ‘‘run’’) Results in intense euphoria (‘‘rush’’) as well as increased wakefulness, alertness, self-confidence, and ability to concentrate. Use also increases motor activity and sexual urge and decreases appetite. Marijuana Marijuana Marijuana (“cannabis,” “grass”) is a collective term for the psychoactive constituents in crude extracts of the plant Cannabis sativa. Active constituents include; Delta-9-tetrahydrocannabinol Cannabinol Cannabidiol Marijuana Delta-9-tetrahydrocannabinol: it acts as an agonist to inhibit adenylyl cyclase through G-protein–linked cannabinoid receptors, whose normal CNS function is unknown. Cannabinol: account for most CNS effects, are localized to cognitive and motor areas of the brain. Cannabinol CB2-receptors are found in the immune system among other peripheral organs Cannabidiol: no reported psychoactive effects. Marijuana Marijuana is mostly smoked, but can be taken orally. It is very lipid soluble. The effects of smoking are immediate and last up to 2–3 hours. Marijuana CNS effects of marijuana include a feeling of being “high,” with euphoria, disinhibition, uncontrollable laughter, changes in perception, and achievement of a dream-like state. Mental concentration may be difficult. Vasodilation occurs, and the pulse rate is increased. Habitual users show a reddened conjunctiva. Marijuana The initial phase of marijuana use (the ‘‘high’’) consists of euphoria, uncontrolled laughter, loss of sense of time, and increased introspection. The second phase includes relaxation, a dreamlike state, sleepiness, and difficulty in concentration. At extremely high doses, acute psychosis with depersonalization has been observed. Marijuana The physiologic effects of marijuana include increased pulse rate and a characteristic reddening of the conjunctiva. Marijuana, and its analogue dronabinol, is used therapeutically to decrease intraocular pressure for the treatment of glaucoma, as an antiemetic in cancer chemotherapy, and to stimulate appetite in patients with AIDS Marijuana Adverse effects of marijuana, some of which are controversial, include the following: Long-term effects similar to those of cigarette smoking, including periodontal disease. Exacerbation of preexisting paranoia or psychosis ‘‘Amotivational syndrome,’’ may be more related to user’s personality type Impairment of short-term memory and disturbances of the immune, reproductive, and thermoregulatory systems