Pentobarbitone premedication for anaesthesia. The influence of the preparation and route of administration on its clinical action.

Studies were carried out in the pre-operative period on patients premedicated with 100 mg pentobarbitone given by mouth or by intramuscular injection into the buttock. The injections were given by doctors using a 4 cm needle or by nurses using the needle of their choosing and two preparations were used. One was a freshly prepared aqueous solution and the other the commercially available organic solution (Nembutal) with propylene glycol, alcohol and water as solvents. An unacceptably high incidence of persistent injection site pain occurred after the use of the organic preparation but not with the aqueous solution. Otherwise no difference was detected between the effects of the two preparations. Drugs injected by doctors were, on the whole, more effective as premedicants than those injected by nurses. Oral pentobarbitone was not as effective a premedicant as the intramuscular preparation and its anxiolytic action did not differ from that of the placebo. Relief of apprehension was disappointing with all preparations of 100 mg pentobarbitone and was not as good as with diazepam. This may be attributed to the use of too small doses but larger injection volumes would have caused their own problems.