The abuse of cocaine and other psychostimulants reflects a complex interaction between the pharmacology of the drug, the personality and expectations of the user, and the environmental context in which the drug is used1. Polydrug abuse involving the concurrent use of several drugs with different pharmacologic effects is increasingly common. Sometimes one drug is used to enhance the effects of another, as with the combined use of cocaine and nicotine, benzodiazepines and methadone, or cocaine and heroin in methadone-maintained patients. Some forms of polydrug abuse, such as the combined use of IV heroin and cocaine, are especially dangerous and account for many hospital emergency room visits.
Chronic cocaine and psychostimulant abuse may cause a number of adverse health consequences and may exacerbate preexisting disorders such as hypertension and cardiac disease. The combined use of two or more drugs may accentuate medical complications associated with abuse of one drug. Chronic drug abuse is often associated with immune system dysfunction and increased vulnerability to infections, including risk for HIV infection. In addition, concurrent use of cocaine and opiates (the “speedball”) is frequently associated with needle sharing by IV drug users. IV drug abusers continue to be the largest single group of persons with HIV infection in several major metropolitan areas in the United States as well as in many parts of Europe and Asia.
Stimulants and hallucinogens have been used to induce euphoria and alter consciousness for centuries. Cocaine and marijuana are two of the most commonly abused drugs today. Synthetic variations of marijuana and a variety of hallucinogens have become popular recently, and new drugs are continually being developed. This chapter describes the subjective and adverse medical effects of cocaine, marijuana, and lysergic acid diethylamide (LSD), as well as methamphetamine, 3,4-methylenedioxy-N-methamphetamine (MDMA), synthetic cathinones (bath salts), phencyclidine (PCP), Salvia divinorum, and other drugs of abuse (flunitrazepam, γ-hydroxybutyric acid [GHB], ketamine). Some options for medical management of severe adverse effects are also described.
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Cocaine is a stimulant and a local anesthetic with potent vasoconstrictor properties. The leaves of the coca plant (Erythroxylum coca) contain ~0.5–1% cocaine. The drug produces physiologic and behavioral effects after oral, intranasal, IV, or inhalation/smoking routes of administration. The reinforcing effects of cocaine are related to activation of dopaminergic neurons in the mesolimbic system (Chap. 60). Cocaine increases synaptic concentrations of the monoamine neurotransmitters dopamine, norepinephrine, and serotonin by binding to transporter proteins in presynaptic neurons and blocking reuptake.
Cocaine is widely available and is abused in virtually all social and economic strata of society. In 2012, an estimated 1.6 million persons in the United States used cocaine, and 1.1 million abused or were dependent on cocaine. Emergency room admissions involving cocaine totaled 505,224 in 2011. Cocaine abuse is prevalent in the general population and in heroin-dependent persons, including those in methadone maintenance programs. IV cocaine is often used concurrently with IV heroin in a combination called a “speedball.” This combination purportedly attenuates the postcocaine “crash” and substitutes a cocaine “high” for the heroin “high” blocked by methadone.
There has been an increase in both IV administration and inhalation of pyrolyzed cocaine via smoking. Following intranasal administration, changes in mood and sensation are perceived within 3–5 min, and peak effects occur at 10–20 min. These effects rarely last more than 1 h. Inhalation of pyrolyzed materials includes inhaling crack/cocaine or smoking coca paste, a product made by extracting cocaine preparations with flammable solvents, and cocaine free-base smoking. Free-base cocaine, including the free-base prepared with sodium bicarbonate (crack), has become increasingly popular because of its relative high potency and rapid onset of action (8–10 seconds following smoking).
Cocaine produces a brief, dose-related stimulation and euphoria and an increase in cardiac rate and blood pressure. Body temperature usually increases following cocaine administration, and high doses of cocaine may induce lethal pyrexia or hypertension. Because cocaine inhibits reuptake of catecholamines at adrenergic nerve endings, it potentiates sympathetic nervous system activity. Cocaine has a short plasma half-life of approximately 45–60 min. Cocaine is metabolized by plasma esterases, and cocaine metabolites are excreted in urine. The brief duration of the euphorigenic effects of cocaine reported by chronic abusers is probably due to both acute and chronic tolerance. Cocaine may be used as often as two to three times per hour. Alcohol is often used to modulate both the cocaine high and the dysphoria associated with the abrupt disappearance of cocaine’s effects. A metabolite of cocaine, cocaethylene, has been detected in blood and urine of persons who concurrently abuse alcohol and cocaine. Cocaethylene induces changes in cardiovascular function similar to those of cocaine alone, and the pathophysiologic consequences of the concurrent abuse of alcohol plus cocaine may be additive.
Cocaine may cause serious medical consequences by any route of administration. The prevalent assumption that cocaine inhalation or IV administration is relatively safe is contradicted by reports of death from respiratory depression, cardiac arrhythmias, and convulsions associated with cocaine use. In addition to generalized seizures, neurologic complications may include headache, ischemic or hemorrhagic stroke, or subarachnoid hemorrhage. Disorders of cerebral blood flow and perfusion in cocaine-dependent persons have been detected with magnetic resonance spectroscopy (MRS). Inhalation of crack cocaine may lead to severe pulmonary disease due to the direct effects of cocaine and to residual contaminants in the smoked material. Hepatic necrosis may occur following chronic crack/cocaine use. Protracted cocaine abuse may also cause paranoid ideation and visual and auditory hallucinations, a state that resembles alcoholic hallucinosis.
Although men and women who abuse cocaine may report that the drug enhances libidinal drive, chronic cocaine use causes significant loss of libido and adversely affects sexual function. Impotence and gynecomastia have been observed in male cocaine abusers, and these abnormalities often persist for long periods following cessation of drug use. Cocaine abuse may produce major derangements in menstrual cycle function including galactorrhea, amenorrhea, and infertility in women and in a rhesus monkey model of cocaine self-administration. Chronic cocaine abuse may cause persistent hyperprolactinemia as a consequence of disordered dopaminergic inhibition of prolactin secretion by the anterior pituitary. Cocaine abuse by pregnant women, particularly crack smoking, has been associated with both an increased risk of congenital malformations in the fetus and perinatal cardiovascular and cerebrovascular disease in the mother. However, cocaine abuse per se is probably not the sole cause of these perinatal disorders, because maternal cocaine abuse is often associated with poor nutrition and prenatal health care as well as polydrug abuse that may contribute to the risk for perinatal disease.
Psychological dependence on cocaine, indicated by inability to abstain from frequent compulsive use, has been reported. Although the occurrence of withdrawal syndromes involving psychomotor agitation and autonomic hyperactivity remains controversial, severe depression (“crashing”) following cocaine intoxication may accompany drug withdrawal.
TREATMENT: Cocaine Overdose and Chronic Abuse
Treatment of cocaine overdose is a medical emergency that is best managed in an intensive care unit. Cocaine toxicity produces a hyperadrenergic state characterized by hypertension, tachycardia, tonic-clonic seizures, dyspnea, and ventricular arrhythmias. IV diazepam in doses up to 0.5 mg/kg administered over an 8-h period has been shown to be effective for control of seizures. Ventricular arrhythmias have been managed successfully by administration of 0.5–1.0 mg of propranolol IV. Because many instances of cocaine-related mortality have been associated with concurrent use of other illicit drugs (particularly heroin), the physician must be prepared to institute effective emergency treatment for multiple drug toxicities.
Treatment of chronic cocaine abuse requires the combined efforts of primary care physicians, psychiatrists, and psychosocial care providers. Early abstinence from cocaine use is often complicated by symptoms of depression and guilt, insomnia, and anorexia, which may be as severe as those observed in major affective disorders. Individual and group psychotherapy, family therapy, and peer group assistance programs are often useful for inducing prolonged remission from drug use. Although psychotherapy may be helpful, no specific form of psychotherapy or behavioral modification is uniquely beneficial.
A number of medications used for the treatment of various medical and psychiatric disorders have been administered to reduce the duration and severity of cocaine abuse and dependence. The search for a medication that is both safe and highly effective for cocaine detoxification or maintenance of abstinence is continuing. Clinical trials of buspirone (BuSpar), a nonbenzodiazepine anxiolytic with dopamine D3 and D4 receptor antagonist properties, are ongoing. Buspirone reduced use of cocaine, nicotine, and cocaine plus nicotine in combination in a nonhuman primate model of stimulant addiction.
Another approach to reducing cocaine abuse is the development of vaccines to actively immunize against cocaine or to functionally antagonize cocaine by preventing it from reaching the brain. Cocaine is converted into inactive metabolites by the plasma enzyme, butyrylcholinesterase (BChE). When this enzyme is modified to increase its catalytic efficiency and accelerate cocaine metabolism, it can both prevent and reverse cocaine-induced toxicity in animals. Importantly, it remains effective even when high doses of cocaine are administered. Ongoing development of this approach includes cocaine hydrolase gene therapy. Vaccines for both cocaine and nicotine have been designed and shown to be safe and somewhat effective in clinical trials. Individual variability in antibody titers and difficulties in determining the optimally effective antibody titer that will neutralize responses to increasing doses of cocaine and have a relatively long duration of action are among the challenges that remain to be resolved.
Cannabis sativa contains >400 compounds in addition to the psychoactive substance, delta-9-tetrahydrocannabinol (THC). Marijuana cigarettes are prepared from the leaves and flowering tops of the plant, and a typical marijuana cigarette contains 0.5–1 g of plant material. The usual THC concentration varies between 10 and 40 mg, but concentrations <100 mg per cigarette have been detected. Hashish is prepared from concentrated resin of C. sativa and contains a THC concentration of between 8 and 12% by weight. “Hash oil,” a lipid-soluble plant extract, may contain THC between 25 and 60% and may be added to marijuana or hashish to enhance its THC concentration. Smoking is the most common mode of marijuana or hashish use. During pyrolysis, <150 compounds in addition to THC are released in the smoke. Although most of these compounds do not have psychoactive properties, they may have physiologic effects.
THC is quickly absorbed from the lungs into blood and then rapidly sequestered in tissues. THC is metabolized primarily in the liver, where it is converted to 11-hydroxy-THC, a psychoactive compound, and >20 other metabolites. Many THC metabolites are excreted through the feces at a relatively slow rate of clearance compared with most other psychoactive drugs.
Specific cannabinoid receptors (CB1 and CB2) have been identified in the central and peripheral nervous system. High densities of cannabinoid receptors have been found in the cerebral cortex, basal ganglia, and hippocampus. T and B lymphocytes also contain cannabinoid receptors, and these appear to mediate the anti-inflammatory and immunoregulatory properties of cannabinoids. A naturally occurring THC-like ligand has been identified and is widely distributed in the nervous system.
Herbal marijuana alternatives are also available. These are usually a combination of several herbs and synthetic cannabinoids. “Spice” and “K2” are among the best known, but many formulations exist, and marijuana is undetectable by the usual methods. These compounds are marketed on the Internet as containing no illegal ingredients. However a number of synthetic cannabinoids are now classified as Schedule I by the Drug Enforcement Administration due to reports of toxicity.
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