Chapter 13: Opioids
Opium was used in its raw form for centuries, both medicinally and for pleasure. Originating in the Middle East, its use spread to Egypt, Greece, China, India, and Europe, and it had significant influence on medicine, literature, and world politics. Opium is produced for only a few days of the opium poppy's life. The raw opium collected from the plant can be taken orally or smoked. The active agent, morphine, can be extracted from opium and used in a variety of ways. Codeine is also extracted from opium. A simple chemical alteration of morphine results in heroin.
Dependence on opioids has been recognized for a long time, but no concerted effort to control dependence occurred until the patent medicine era. Increased regulation resulted in a change in the typical opioid user—from a middle-aged, middle-class woman using legal patent medicines to an inner-city user of illicit injectable heroin. Heroin use grew again in the 1960’s, along with overall use of illicit drugs. Use also increased among troops stationed in Vietnam. Subsequent studies found that most soldiers quit when they returned home. This experience indicated that under certain conditions, a relatively high percentage of individuals will use opioids recreationally but that opioid dependence is not inevitable among occasional users.
Both the natural products of the opium poppy and the synthetic opioids act on opioid receptors in the brain. These receptors are activated by naturally occurring opioid-like products of the nervous system and endocrine glands. Endorphins and enkephalins are examples of these endogenous opioid-like neurotransmitters. Researchers have also identified opioid antagonists that quickly block the effects of opioids. These can be used to reverse overdose, precipitate withdrawal symptoms and block the positive effects of subsequent doses of opioids.
For medical use, opioids have several beneficial effects, including pain relief, treatment of diarrhea and the resulting dehydration and cough suppression. However, there are many concerns associated with the use of opioids, including overdose, tolerance, physical and psychological dependence and withdrawal. Fast-acting injectable opioids are particularly reinforcing and the most likely form to lead to dependence. Administration of the drug is followed by an increase in pleasure and/or a decrease in discomfort. Through conditioning, the needle habit itself can become reinforcing.
Acute toxicity is a significant risk with the use of opioids, especially in combination with alcohol. The opioid overdose triad consists of coma, depressed respiration and pinpoint pupils. Death can occur from respiratory depression. Chronic toxicity is most associated with the injection method of use because of its association with skin and blood-borne infections.
Not everyone who tries heroin becomes dependent on the drug, but those that do, spend a significant about of time and money maintaining their habit. As withdrawal occurs within hours of the last dose, users may need three to four injections per day to prevent withdrawal. The drugs and its associated paraphernalia are expensive and the potency of heroin varies, increasing the risk of unintentional overdose.Although heroin receives a great deal of publicity, usage rates are low, with about 0.1% of Americans reporting use in the past year. Rates of nonmedical use of prescription pain relievers are higher, with about 5% of adults reporting past-year use. Overall, there are about 500,000 opioid-dependent Americans and two to three times that many chippers, or occasional heroin users. Illicit heroin used in the U.S. currently comes primarily from South America, Mexico and Asia.