Effect of Levallorphan and Nalorphine upon Barbiturate-Induced Respiratory Depression in Rats.

Abstract
Respiratory depression (50% depression of tidal air) in rats produced by phenobarbital, barbital, Amytal and Seconal could not be relieved by doses of nalorphine or levallorphan which could be tolerated. Some reduction in respiratory depression caused by pento-barbital was seen when doses of either of the above drugs exceeded that of the pentobarbital by a factor of two.