Drugs of Abuse
Drugs of Abuse
Drugs of abuse are commonly classified by their pharmacological and behavioral effects into six categories: (1) opiate analgesics, (2) stimulants, (3) depressants, (4) hallucinogens, (5) inhalants, and (6) anabolic steroids. Most of these drugs mimic endogenous neurotransmitters that are naturally present in the human body and regulate certain processes within the central and peripheral nervous systems. Because the quantity of drugs consumed by abusers typically far exceeds the level that naturally occurs in the body, the effects on neurons can range from subtle changes associated with tolerance (i.e., reduced sensitivity) to cell damage or cell death.
Dependence liability refers to the risk that repetitive use of a drug will lead to physical or psychological dependence, also known as addiction. Alcohol and tobacco have by far the highest rates of documented physical dependence in the United States (see table 1). Moreover they have high dependence liabilities: Roughly one-third of individuals who repeatedly smoke tobacco will develop nicotine dependence, and approximately 15 percent of those who repeatedly drink alcohol will become alcoholic. These dependence liabilities are comparable to or exceed those of cocaine, stimulants, and heroin. Although it has been asserted that cannabis is not addictive, Alan Budney and John Hughes pointed out in a 2006 article that nearly one in ten people who smoke marijuana will come to satisfy diagnostic criteria for dependence, including compulsive usage and withdrawal symptoms of mild to moderate severity.
| Dependence Liability of Drugs of Abuse in the United States | ||
|---|---|---|
| Drug | Proportion of U.S. population with a history of dependence | Proportion of abusers who became dependent |
| SOURCE: Anthony, Warner, and Kessler 1994 (figures rounded to the nearest whole-number percent). | ||
| Tobacco | 24% | 32% |
| Alcohol | 14% | 15% |
| Cannabis | 4% | 9% |
| Cocaine | 3% | 17% |
| Stimulants | 2% | 11% |
| Heroin | <1% | 23% |
| Other opiates | <1% | 8% |
| Hallucinogens | <1% | 5% |
| Benzodiazepines | 1% | 9% |
| Inhalants | <1% | 4% |
OPIATE ANALGESICS
Opiates are drugs derived from the opium poppy plant that have analgesic and sedative qualities commonly used to treat pain. Examples include opium, heroin, and morphine. Synthetic analogs of these drugs, which are called opioids, have been created in the laboratory. Examples include methadone, hydrocodone, and oxycodone. The short-term psychoactive effects of opioids involve euphoria, drowsiness, and impaired motor and cognitive functioning. Because opiates and opioids also inhibit activity in brain regions that regulate basic functions such as respiration, they can precipitate death by suffocation. The risks increase dramatically when these drugs are combined with alcohol or other depressants. All opiates and opioids have a high potential for abuse and dependence, which increase with higher potency of the drug and more efficient routes of administration, such as injection or smoking. Injection practices also carry additional health risks from communicable diseases such as HIV/AIDS and hepatitis.
STIMULANTS
Stimulants such as amphetamines increase the activity of one or more of the monoamine neurotransmitters (dopamine, norepinephrine, and serotonin). Activation of the dopamine system is primarily responsible for the euphoric effects, or “rush,” of stimulants. Stimulants also enhance mood, promote wakefulness, increase respiration and blood pressure, and decrease appetite. Chronic abuse of stimulants can severely damage nerve cells and cause an array of psychiatric disturbances, including psychosis and paranoia, as well as motor disturbances, including tics.
Methamphetamine, sometimes known as “ice” or “crank,” is the product of a “street” modification of amphetamine using over-the-counter decongestants. It has an even greater stimulant effect on the dopamine system. In addition some of the precursor chemicals and solvents used to manufacture methamphetamine can be highly toxic and flammable, leading to serious safety risks from inhalation and potential explosions or fires. Methamphetamine can be taken orally, intranasally, intravenously, or by smoking. Abuse of methamphetamine has been associated with serious physical dependence and severe health consequences, including nervousness and agitation, tactile hallucinations, and paranoid psychosis, of which hallucinations and delusions may be refractory to treatment.
“Designer” stimulants such as “ecstasy” (methylenedioxymethamphetamine, or MDMA) have potent effects on norepinephrine and serotonin in addition to dopamine. This elicits psychedelic or hallucinogenic reactions in addition to euphoria. Because norepinephrine affects the autonomic system, it can also precipitate rapid heart rate, increased blood pressure, and an elevated risk of cardiovascular events. MDMA intoxication enhances the pleasure of tactility, and users often seek physical contact with others. This may be observed at MDMA parties, or “raves,” where users may dance closely or aggressively with each other. Withdrawal from MDMA can precipitate disturbances in mood, insomnia, fatigue, and depression. Similar to methamphetamine, MDMA abuse can cause chronic damage to the brain.
Cocaine is a potent and highly addictive stimulant that can be snorted or injected. Cooking sodium bicarbonate (i.e., baking soda) with cocaine enables it to be smoked in the crystallized form of “crack,” which delivers a more potent yet shorter-lived high that may last only a few minutes. This rapid cycle of acute intoxication and withdrawal (or “crash”) has the potential to elicit sustained binge patterns and severe addiction to the drug. In addition to the health risks typically associated with stimulant abuse, the chemical properties of cocaine—such as its acidity and its typical intranasal method of delivery—can cause damage to nasal and sinus tissue.
DEPRESSANTS
Depressants represent a broad class of drugs that include anxiolytics, hypnotics, and sedatives. The most commonly abused depressant is alcohol. Benzodiazepines, which act on the inhibitory neurotransmitter GABA, are the second most commonly abused depressant and among the most commonly prescribed medications. Benzodiazepines prescribed for anxiety are called anxiolytics, while those prescribed for insomnia are called hypnotics. They have a wide therapeutic profile, covering the spectrum of sedation from minor tranquilizers to preoperative anesthetics. Acute side effects can range from mild memory loss to anterograde amnesia for new events occurring while intoxicated. The anterograde amnesia may be worsened when the drug is combined with alcohol. Few deaths have been attributed to benzodiazepine ingestion alone. It has been suggested that long-term use might cause permanent impairment of motor and cognitive functioning. But despite being in use for over forty years, its long-term effects are still uncertain.
Barbiturates are an older class of depressants that were prescribed similarly for anxiety and sedation. They were associated with serious side effects and had a relatively narrow therapeutic profile. Any mixture of barbiturates with alcohol has the potential to precipitate seizures, a severe withdrawal syndrome, or death. As a result their use has been almost totally usurped by benzodiazepines, and they are now prescribed only rarely for the treatment of convulsions or refractory migraine headaches.
HALLUCINOGENS
Most hallucinogens exist naturally in certain plants (e.g., mescaline and peyote). Others, such as LSD (lysergic acid diethylamide), are synthesized from ergot, a mold that grows on rye and other grains. Hallucinogens cause sensory or perceptual alterations that can be visual, auditory, tactile, olfactory (smell), or gustatory (taste). They can also cause thought disturbances, such as grandiose or paranoid thinking, and can lead to feelings of irrational pleasure or panic. Intense panic can lead to bizarre or dangerous behavior and have long-lasting psychiatric repercussions similar to those of post-traumatic stress disorder (PTSD). Hallucinogens act primarily on the serotonin system, which, like MDMA, can elicit psychotic-like experiences.
Cannabis, or marijuana, is the most widely used illegal drug in the United States. Cannabis contains delta-9-tetrahydrolcannabinol (THC), a psychoactive chemical that binds to naturally occurring cannabinoid receptors in several brain regions, including the hippocampus. The precise mechanism of action of THC is unclear. According to the FDA, cannabis has no legitimate medical usage; however, a synthetic analog of THC called dronabinol may be used medicinally as an appetite stimulant, to reduce nausea and pain, or to reduce intraocular pressure in glaucoma patients. Cannabis is typically smoked, but it can also be cooked and eaten with high-fat foods. Many users report feelings of euphoria, relaxation, and perceptions of heightened awareness, whereas others report mild to moderate levels of anxiety and paranoia. Long-term side effects of chronic use of cannabis may include reductions in sperm motility, increased estrogen levels, and decreased high-density (“good”) cholesterol. Although an “amotivational syndrome” characterized by impaired ambition and substandard productivity has been anecdotally attributed to long-term cannabis use, the existence of this syndrome has not been scientifically established. No deaths have been reliably attributed to cannabis ingestion, apart from vehicular or other accidents stemming from impaired judgment or motor coordination.
ANABOLIC STEROIDS
Anabolic-androgenic steroids (AAS) are synthetic forms of the primary male sex hormone, testosterone. The major consumers of illegally obtained AAS are bodybuilders and athletes, who seek their anabolic properties for athletic or aesthetic gains while also attempting to minimize their androgenic properties, which elicit most of the unwanted side effects. The dangers of AAS are clearly documented, even when they are used according to prescription standards. Documented adverse physical risks include permanent liver injury, increased blood pressure and risk of stroke, acne, hair loss, and sudden cardiac death. Males may experience testicular atrophy and the development of female sex characteristics such as breast enlargement. Female users may develop masculine characteristics such as facial hair and voice deepening as well as menstrual irregularities and clitoral enlargement. The psychiatric effects of AAS abuse can be unpredictable and range from elevated mood to sudden and irrational aggressiveness. Upon cessation of AAS, particularly after sustained high doses, users may experience depression and withdrawal, lowered energy, decreased libido, and a precipitous loss of muscle mass. All AAS carry a risk of physical and psychological dependence.
INHALANTS
Inhalant abuse, or “huffing,” involves the deliberate intake of fumes from solvents (e.g., paint thinner) or aerosol gases used as propellants (called “whippets”). Inhalant intoxication may appear similar to alcohol intoxication, but the subjective effects are reported to be more anesthetic than those of alcohol. Solvent inhalants are corrosive
| Table 2: U.S. Drug Enforcement Administration Schedule of Controlled Substances | ||
|---|---|---|
| U.S. Drug Enforcement Administration Schedule of Controlled Substances | ||
| Schedule | Examples | Abuse potential and prescription practices |
| SOURCE: United States Controlled Substances Act, 21 U.S.C. § 802 et seq | ||
| I | Heroin, cannabis, LSD. | Illicit. |
| II | High-potency opioid analgesics(e.g., oxycodone), high-potency stimulants(e.g., methylphenidate or Ritalin). | High abuse potential. Rx must be handwritten, no refills permitted. |
| III | Low-potency opioid preparations (e.g., codeine cough suppressant), anabolic steroids. | Moderate abuse potential. Verbal Rx’s permitted, 5 refills permitted up to 6 months. |
| IV | Most prescription sedatives and sleep aids (e.g., benzodiazepines, Ambien). | Low to moderate abuse potential. Verbal Rx’s permitted, 5 refills permitted up to 6 months. |
to tissue and extremely dangerous to inhale in concentrated forms. All huffing temporarily deprives the brain of oxygen, and anoxia is a risk to all inhalant abusers. Inhalant abuse can cause severe adverse health effects, including damage to the heart, lungs, liver, and kidneys. Inhalant abuse can also lead to acute amnesia, stroke, coma, and death.
LAW ENFORCEMENT EFFORTS
In the United States the Drug Enforcement Administration (DEA) “schedules” drugs according to whether they have (1) a legitimate medical usage and (2) a potential liability for abuse or dependence. Similar scheduling mechanisms are employed by many other countries as well. If the U.S. Food and Drug Administration (FDA) determines that a drug of abuse has no legitimate medical usage, then it is classified as Schedule I by the DEA. Drugs with legitimate medical uses are classified into Schedules II through IV, depending on their abuse potential (see table 2). The schedule has important implications for prescription practices, including permissible refills and the need for handwritten, as opposed to verbal, prescription orders. Issues of toxicity and side-effect profiles do not influence scheduling by the DEA, but they do influence the FDA’s approval of medications for specific conditions, based upon a balancing of each medication’s risks versus benefits.
Tobacco and alcohol each have a moderate to high abuse potential and no legitimate medical usage (not to mention high mortality and morbidity risks), yet they are neither regulated by the FDA nor scheduled by the DEA. Instead, largely for policy reasons, they are regulated by the U.S. Bureau of Alcohol, Tobacco, and Firearms (ATF) with regard to such matters as licensing and regulation of sales.
DEMOGRAPHIC USE PATTERNS
In 2005 rates of substance abuse or dependence in the United States varied to some degree by racial or ethnic group. However, they did not vary across the most populous demographics of Caucasians, African Americans, and Hispanics (see table below).
Despite similar use-prevalence patterns, Hispanics in the United States are imprisoned at more than twice the rate of Caucasians for drug-related offenses, while African
| Rates of Substance Abuse and Dependence in the U.S. by Racial and Ethnic Census Category | |
|---|---|
| Racial/Ethnic Group | Percentage |
| SOURCE: Office of Applied Studies 2006. | |
| American Indians/Alaskan Natives | 21.0% |
| Pacific Islanders | 11.0% |
| Caucasians | 9.4% |
| Hispanics | 9.3% |
| African-Americans | 8.5% |
| Two or more races | 10.9% |
Americans are imprisoned at nearly four times the rate of Caucasians (Bureau of Justice Statistics 2006). These apparent discrepancies might be attributable to differential law enforcement practices. For instance, police might focus greater attention on minority communities, or prosecutors might offer minority defendants fewer opportunities for plea bargains or diversionary programs. In addition sentencing guidelines could contribute to unintended disparate impacts on minority groups. For example, there is some indication that crack-cocaine may be used relatively more frequently among African American individuals in urban environments, whereas methamphetamine may be used more frequently among Caucasians in rural environments. Higher penalties can attach in the United States to the crack form of cocaine, as compared to its powder form, and this might account in part for higher incarceration rates among African Americans. With newer laws being enacted to stem the rising tide of methamphetamine abuse, changes might also be seen in demographic patterns among arrestees and inmates. More research is required to gain a better understanding of this important issue and to plan for effective corrective actions.
SEE ALSO Hallucinogens; Psychotropic Drugs
BIBLIOGRAPHY
Anthony, J. C., L. A. Warner, and R. C. Kessler. 1994. Comparative Epidemiology of Dependence on Tobacco, Alcohol, Controlled Substances, and Inhalants: Basic Findings from the National Comorbidity Study. Experimental and Clinical Psychopharmacology 2: 244–268.
Booth, Brenda M., Carl Leukefekd, Russel Falck, and Robert G. Carlson. 2006. Correlates of Rural Methamphetamine and Cocaine Users: Results from a Multi-State Community Study. Journal of Studies on Alcohol 67 (4): 493–501.
Budney, Alan J., and John R. Hughes. 2006. The Cannabis Withdrawal Syndrome. Current Opinions in Psychiatry 19 (3): 233–238.
Bureau of Justice Statistics. 2006. Prisoners in 2004. Washington, DC: U.S. Department of Justice.
Dawkins, Marvin P., and Mary M. Williams. 1997. Substance Abuse in Rural African-American Populations. In Rural Substance Abuse: State of Knowledge and Issues, eds. Elizabeth B. Robertson et al., 484–487. National Institute on Drug Abuse Research Monograph 168. Rockville, MD: U.S. Department of Health and Human Services, National Institutes of Health, National Institute on Drug Abuse.
Substance Abuse and Mental Health Services Administration (SAMSHA). 2006. Results from the 2005 National Survey on Drug Use and Health. Washington, DC: SAMSHA, Office of Applied Studies. http://www.oas.samsha.gov.
Douglas B. Marlowe
Nicholas S. Patapis