The abstinence syndrome that occurs in the morphine addict may be taken as the prototype. The first 8 to 16 h of abstinence usually pass asymptomatically. At the end of this period, yawning, rhinorrhea, sweating, piloerection, and lacrimation are manifest. Mild at first, these symptoms increase in severity over a period of several hours and then remain constant for several days. The patient may be able to sleep during the early abstinence period but is restless, and thereafter insomnia remains a prominent feature. Dilatation of the pupils, recurring waves of “gooseflesh,” and twitching of the muscles appear. The patient complains of aching in the back, abdomen, and legs and of “hot and cold flashes”; he frequently asks for blankets. At about 36 h the restlessness becomes more severe, and nausea, vomiting, and diarrhea usually develop. Temperature, respiratory rate, and blood pressure are slightly elevated. All these symptoms reach their peak intensity 48 to 72 h after withdrawal and then gradually subside. The opioid abstinence syndrome is rarely fatal (it is life-threatening only in infants). After 7 to 10 days, the clinical signs of abstinence are no longer evident, although the patient may complain of insomnia, nervousness, weakness, and muscle aches for several more weeks, and small deviations of a number of physiologic variables can be detected with refined techniques for up to 10 months (protracted abstinence).
Habituation, the equivalent of emotional or psychologic dependence, refers to the substitution of drug-seeking activities for all other aims and objectives in life. It is this feature that fosters relapse to the use of the drug long after the physiologic (“nonpurposive”) abstinence changes seem to have disappeared. The cause for relapse is not fully understood. Theoretically, fragments of the abstinence syndrome may remain as a conditioned response, and these abstinence signs may be evoked by the appropriate environmental stimuli. Thus, when a “cured” addict returns to a situation where narcotic drugs are readily available or in a setting that was associated with the initial use of drugs, the incompletely extinguished drug-seeking behavior may reassert itself.
The characteristics of addiction and of abstinence are qualitatively similar with all drugs of the opiate group as well as the related synthetic analgesics. The differences are quantitative and are related to the differences in dosage, potency, and length of action. Heroin is 2 to 3 times more potent than morphine but the heroin withdrawal syndrome encountered in hospital practice is usually mild in degree because of the low dosage of the drug in the street product. Dilaudid (hydromorphone) is more potent than morphine and has a shorter duration of action; hence the addict requires more doses per day, and the abstinence syndrome comes on and subsides more rapidly. Abstinence symptoms from codeine, while definite, are less severe than those from morphine. The addiction liabilities of propoxyphene, a weak opioid, are negligible. Abstinence symptoms from methadone are less intense than those from morphine and do not become evident until 3 or 4 days after withdrawal; for these reasons methadone can be used in the treatment of morphine and heroin dependency (see further on). Meperidine addiction is of particular importance because of its high incidence among physicians and nurses. Tolerance to the drug’s toxic effects is not complete, so that the addict may show tremors, twitching of muscles, confusion, hallucinations, and sometimes convulsions. Signs of abstinence appear 3 to 4 h after the last dose and reach their maximum intensity in 8 to 12 h, at which time they may be worse than those of morphine abstinence.