Studies of Drugs Given Before Anaesthesia VI: The Phenothiazine Derivatives

Abstract

summary Fourteen phenothiazine derivatives and two phenothiazine-like drugs have been given in premedication under standard conditions, and sometimes at more than one dose level, to evaluate their desired and toxic effects. Their influence on the course of methohexi-tone-nitrous oxide-oxygen anaesthesia was observed, and emetic and other postoperative sequelae noted. Results were compared with those obtained with atropine and atropine plus pethidine. Drugs with dimethylaminopropyl side chains were the most powerful hypnotics but the sedative effect was spoiled by pre-operative restlessness with promethazine and triflupromazine, and this complication was also common in compounds with a piperazine side chain. Hypotension was the most frequent disadvantage of the phenothiazines and was of such severity as to curtail the use of several drugs. Propio-mazine (20–40 mg) and thiethylperazine (10 mg) were least toxic from this point of view. The incidence of excitatory phenomena with methohexitone 1.6 mg/kg varied with the analgesic or antanalgesic action of the premedication. Emetic sequelae were infrequent but perphenazine 5 mg showed most promise as an anti-emetic. Oculogyric crises occurred frequently after 1.2–2.5 mg fluphenazine and were also seen after trifluperazine and perphenazine. Their treatment is discussed in detail.