A new series of potent analgesics: dextro 2:2-diphenyl-3-methyl-4-morpholinobutyrylpyrrolidine and related basic amides. II. Comparative analgesic activity, acute toxicity and tolerance development in rats for R875, morphine, pethidine and methadone.

Abstract

Abstract The analgesic activity, acute toxicity and development of tolerance of R875, morphine, pethidine and methadone after subcutaneous administration in rats have been measured. In this animal, R875 is shown to be several times more active than the three other compounds. R875 has a faster onset of action, higher therapeutic ratios and a slower rate of development of tolerance.