Tramadol--a new analgesic.

Tramadol (Zydol-Searle) is a centrally acting opioid analgesic newly marketed in the UK for use by mouth or injection. It is licensed for the prevention and treatment of moderate to severe pain. The manufacturer claims that it causes less constipation and respiratory depression than conventional opioids and that it offers a special "dual action". We examine the claims and consider the place of tramadol.