Nefopam is a non-narcotic analgesic not structurally related to other analgesic drugs. It is effective by the oral and parenteral routes, and when appropriate dose ratios were compared in short term studies it was shown to produce analgesia comparable to that with the oral analgesics aspirin, dextropropoxyphene and pentazocine, as well as that with 'moderate' doses of parenteral morphine, pethidine and pentazocine. However, when 'higher' dose ratios were compared, morphine and pethidine were usually more effective than nefopam, possibly due to a 'ceiling effect' for analgesia which may occur with higher doses of nefopam, as with other simple analgesics. Although a few patients with chronic pain have received nefopam for several weeks, further studies are needed to clarify its continued effectiveness and safety when used over long periods. In most patients nefopam has been relatively well tolerated, the most frequent side effects being sweating, nausea and in some studies sedation.