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Opioid analgesics have been used since at least 300 B.C. Nepenthe (Greek “free from sorrow”) helped the hero of the Odyssey, but widespread opium smoking in China and the Near East has caused harm for centuries. Since the first chemical isolation of opium and codeine 200 years ago, a wide range of synthetic opioids have been developed, and opioid receptors were cloned in the 1990s. Two of the most important adverse effects of all these agents are the development of opioid use disorder and overdose. Prescription opioids are primarily used for pain management, but due to ease of availability individuals procure and misuse these drugs with dire consequences. In 2015, for example, 3.8 million individuals in the United States were current misusers of pain relievers. More concerning, during 2015 >20,000 overdose deaths involved opioids with an additional 12,990 overdose deaths related to heroin alone. These numbers continue to increase and have accelerated due to mixing high potency fentanyl derivatives with heroin. The accelerating death rates are partially because reversal of fentanyl overdoses can require several-fold larger doses of naloxone than the doses in the intranasal devices used for nonmedical street resuscitations. Indeed, according to the most recent World Drug Report, opioid misuse causes the greatest global burden of morbidity and mortality; disease transmission; increased health care, crime, and law enforcement costs; and less tangible costs of family distress and lost productivity.
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The terms “dependence” and “addiction” are no longer used to describe substance use disorders. Opioid-related disorders encompass opioid use disorder, opioid intoxication, and opioid withdrawal. The diagnosis of opioid use disorder as defined in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) requires the repeated use of the opiate while producing problems in two or more areas in a 12-month period. The areas include tolerance, withdrawal, use of greater amounts of opioids than intended, craving, and use despite adverse consequences. This new definition of opioid use disorder, reducing the criteria for diagnosis from three problem areas to two, is not expected to change the rates of these disorders because most individuals using these substances meet more than three criteria.
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A striking recent aspect of illicit opioid use has been its marked increase as the gateway to illicit drugs in the United States. Since 2007, prescription opiates have surpassed marijuana as the most common illicit drug that adolescents initially use, although overall rates of opioid use are far lower than marijuana. The most commonly used opioids are diverted prescriptions for oxycodone and hydrocodone, followed by heroin and morphine, and—among health professionals—meperidine and fentanyl. Heroin is metabolized into 6-monoacetylmorphine and morphine thus acting as a prodrug that more readily penetrates the brain and is converted rapidly to morphine in the body. Two opioid maintenance treatment agents—methadone and buprenorphine—are also misused, but at substantially lower rates, and the partial opioid agonists such as butorphanol, tramadol, and pentazocine are misused even less frequently. Because ...