How toxic are propoxyphene and ethanol in combination?

Ethanol has been claimed to potentiate greatly the lethality of propoxyphene, although published clinical data suggest only an additive effect. Mice were treated intraperitoneally with various doses of propoxyphene hydrochloride and ethanol. Isobolograms of the data show the combination to be less-than-additive for lethality and loss of motor coordination and, at worst, simply additive for sedation.