Physiologic dependence with opioids

Although statistics on alcoholism are extensive, no one knows how many persons are dependent on prescription sedatives. However, physiologic dependence has been relatively rare and usually occurs following long-term treatment with doses of 40 mg/d or more of diazepam or its equivalent. These abusers often are codependent on other drugs such as opioids, alcohol, or stimulants. "Therapeutic dose dependence" at doses of 15-30 mg/d of diazepam may be characterized by weight loss, changes in perception, paresthesias, and headache. 

Opioid analgesic prototype strong mu receptor agonist. Poor oral bioavailability. Tox constipation, emesis, sedation, respiratory depression, miosis, and urinary retention. Tolerance may be marked high potential for psychologic and physiologic dependence. Additive effects with other CNS depressants. 

However, fear of inducing addiction or respiratory depression interferes with pain management. Addiction is rare in clinical practice. Some patients who are treated with opioid analgesics can develop a tolerance to the medication requiring an increased dose to maintain pain relief. However, the need to increase the dose of the medication is usually related to an increase in pain due to disease progression or complications. Physical dependence on a medication occurs when the physiological condition of the patient is altered. 

Tolerance also results from metabolic changes (enzyme induction) and physiological/behavioural adaptation to drug effects, e.g. opioids. Physical dependence develops to a substantial degree with... 

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