ACQUIRED TOLERANCE TO INTRAVENOUS THIOBARBITURATES IN ANIMALS BY

narcotics as "the partial or complete this with thiopentone, thialbarbitone, immunity to quantities of these substances thiamylal and hexobarbitone. which would otherwise diminish or com- In the course of clinical work the pletely abolish the functional activity of author has encountered several cases of certain neurophysiological and other tolerance to thiobarbiturates, in which the mechanisms. " The repeated administra- patients had been receiving large doses of tion of medium-acting barbiturates leads sedative or analgesic drugs. In none of to the development of tolerance to their these patients could the resistance be narcotic effects. This applies to amylobar- attributed to acquired tolerance to bitone and isopropyl-P-bromallyl-barbitu- medium-acting barbiturates. Similarly the rate in rabbits (Fitch, 1930) and delvinal drugs being administered to each of the and pentobarbitone in guineapigs and rats resistant patients varied daily, but in each (Carmichael, 1941, 1948). The above case they were limited to one type of drug workers and Gruber and Keyser (1946) such as D.D.A. analgesics or aspirin-like have convincingly demonstrated that analgesics