Opioid analgesic drugs in the elderly.

Much is known about opioid metabolism, which is critical in administering these agents to the elderly. Fear of addiction and tolerance are the major barriers to their use among patients as well as health-care professionals. Addressing these issues early in the initiation opioid therapy will help to alleviate these concerns. Once therapy with an opioid is initiated, the role of renal function is critical. Because many metabolites of the opioids are renally cleared and have activity either in analgesia or as undesired side effects, it is critical to be aware of the creatinine clearance (not just serum creatinine) in the elderly. The initiating doses of the opioids can be equal to that of younger patients, but the clinician should anticipate using a longer frequency of dosing interval or smaller doses during the course of therapy. Methadone, propoxyphene, and meperidine are not recommended for use in elderly people, because of the toxicity of their metabolites. Of all the unwanted effects of the opioids, the most difficult to deal with is that of constipation. Here, an aggressive approach using bowel stimulating laxatives is critical in order to prevent this problem. It is anticipated that a variety of newly formulated opioids will shortly be available for clinical use. Finally, as a better understanding of the neurophysiology of pain is gained, the clinician can anticipate having more analgesic opioids that target their receptors without agonist or antagonist effect on other opioid receptors. This will allow the clinician to better relieve pain with a minimum of unwanted side effects.