Analgesic action of ethyl 4-phenylpiperidine-4-carboxylates with oxygenated 1-substituents.

The analgesic potency of a series of new compounds related to pethidine has been measured in rats. The replacement of the methyl group on the nitrogen atom of pethidine by groups containing ether linkages produces an increase in potency. Two different positions for the oxygen atom are particularly beneficial, but the effects, in these two positions, appear to be exerted in different ways and are not additive. Simple toxicity tests in mice and rats and tests on respiration in rats of five of the more potent compounds revealed no unexpected adverse action.