Enhancement of propoxyphene-induced analgesia by doxepin

The activity of the centrally acting analgesic, propoxyphene, either alone or combined with the tricyclic antidepressant, doxepin, has been studied. Doses of doxepin, in themselves lacking any analgesic effect, remarkably enhanced the analgesic activity of propoxyphene, either by the oral or intraperitoneal route. On the other hand, oral toxicity data prove that doxepin does not alter significantly propoxyphene acute toxicity.