A MODIFICATION OF HAFFNER’S METHOD FOR TESTING ANALGESICS

Abstract

A simple method was devised for measuring the intensity of pressure of artery clip was used in Haffner''s tail-pinch method for testing analgesics. By this device various pressures of clips ranged from 50 to 800 g were chosen. This arrangement made it possible to control and to duplicate the intensity of pressure stimulus. The supra-threshold stimulus (500 g) was used for the usual an analgesiometry in order to reduce observer''s error, though normal pain threshold in the present experiment lay between 100 and 300 g. As a criterion for judging analgesia, loss of head turn response and biting behavior were adopted, and they are graded by their reaction time, complete (C) and partial (P) analgesia. By the present modification, it was capable to measure potencies of weak analgesics. ED 50 of various analgesics estimated by the judgement "C" and "C+P" are described. The weak analgesic potencies of phenaeetine and acetyl salicylic acid could be observed but ED 50 of these drugs were difficult to measure.