OPIOIDS ARE THE CLASSIC SOURCE of relief for severe short-term pain. But until recently, physicians have been loath to prescribe them for moderate long-term pain and patients have been wary of taking them because of worries about addiction and side effects.

But better understanding of opioids has shown that, while chronic-pain patients can become physically dependent on these drugs and develop a tolerance to then, that gradually requires escalation doses, that's not the same as addition. It is a physical and psychological problem that compels people to abuse pain-killers and other drugs. Also, careful dosing by doctors skilled in using opioids can avoid many problems. in addition, research has shown that some side effects, such as sedation and nausea, gradually go away with continued use.

The American Geriatrics Society guidelines agree that opioid are "are probably underutilized in the treatment of older people," adding that "fears of drug dependency and addition do not justify the failure to relieve pain." However, many doctors are uncomfortable with these drugs, so you may need to bring in a specialist. Morphine, made from the opium poppy, is the "mother" opioid. But there are also semi-synthetic versions of it (such as codeine) and completely synthetic ones, too (Demerol is probably the most familiar of these).

Opioids work by hooking onto various nerve receptors, which keep sensory messages from traveling through the body to the brain, where they're interpreted as pain. Different drugs block different nerve receptors, which affects the relief you get and what the side effects are.

The newer synthetics have encouraged doctors to prescribe opioids sooner and for less severe chronic pain because they up relief, reduce side effects and require lower doses than older types. There are now long-acting forms, lasting eight to 12 hours instead of three or four which should slow tolerance build-ups. For example, doctors aren’t likely to prescribe oxycodone (Percodan) for chronic pain but now often use controlled-release forms of it (such as Oxycontin) or controlled-release morphine (MS Contin).

Another new option: a synthetic opioid called fentanyl that's now available as a skin patch (Duragesic). It assures even pain relief for three days at lower overall dosing.

On the horizon: prescribing opioids with an "antagonist" drug, such as methylnaltrexone, which appears to prevent side effects like nausea, constipation and itching.