The Effects of Premedication With Phenothiazine Derivatives on the Course of Methohexitone Anaesthesia

Abstract

METHOHEXITONE is a rapidly acting barbiturate (fig. 1) which was originally described by Stoelting in 1957. Within the past year it has been subjected to clinical trials in this country and Jolly (1960) has verified the findings of Wyant and Chang (1959) and Wyant and Barr (1960) that recovery from methohexitone occurs more rapidly than from equivalent doses of thiopentone.

Alterations in Response to Somatic Pain Associated With Anaesthesia

“…Work from this school has shown that the incidence of excitatory phenomena (spontaneous involuntary muscle movements and tremors) following injection of this barbiturate is markedly affected by the analgesic action of the premedication (Dundee and Moore, 1961a;Moore and Dundee, 1961c). With the phenothiazine derivatives, Dundee and Moore (1961c) •demonstrated a very close relationship between the analgesia index of the premedication and the incidence of excitatory phenomena which followed a dose of 1.6 mg/kg methohexitone. Dundee and Moore (1961b) also observed that the pre-operative use of hyoscine increased the incidence of this complication as compared with atropine.…”

Studies of Drugs Given Before Anaesthesia

“…The ampoules can be labelled with a code number, but experience has shown that a copy of this code should always be readily available if needed. On example of the necessity of this was the occurrence of severe bradycardia in a patient who was given two doses of suxamethonium without the anaesthetist being aware that hyoscine had been used as premedication (Dundee and Moore, 1961b). It is obvious that risks of this nature are not justified, simply to be able to say the "blind" method of assessment was employed.…”

“…Pethidine 100 mg with atropine 0-6 mg was given to 176 patients. results obtained by scoring systems (Belville, Bross and Howland, 1959a, b;Dundee et al, 1961). The principles of ridit analysis and the method of calculation are shown in the appendix, using the data given in table II.…”

“…include not only an examination of the degree of sedation and diminution of apprehension which they produce but also an evalution of the effects on the course of the subsequent anaesthesia (Dundee and Moore, 1961a) and an investiption of any postoperative complications associated with their use. A detailed survey must be made of the desired and side effects of the drugs at each of these stages of their action.…”

Dose-Finding and Premedication Studies with Zopiclone

“…Fur thermore, there is wide scope for variation in the drugs that can be studied, which can rea dily be administered by mouth or by intra muscular injection, in random order, and their effects assessed using 'double-blind' techniques [2], With proper selection of both patients and type of surgical operation there are no ethical objections to the use of an inert medication in order to assess the placebo effect. Previously published studies have compared the sedative actions of phenothiazines [3,4], opioids [5], anti-emetic com pounds [6, 7], and benzodiazepines [8, 9].Women of child-bearing age, scheduled for minor gynaecological surgery, other than termination of pregnancy, form an eminently suitable patient population for this design of study. These formed the subjects for the present study which consisted of two parts: (1) a dose-finding study of oral zopiclone, to establish the optimal sedative dose, and (2) a further detailed study of what we considered to be the optimum dose of zopiclone (7.5 mg), with particular reference to the side effects and the time to onset of action.…”