Prolongation of thiopentone anaesthesia by probenecid

In a double-blind study, probenecid 0.5 or 1.0 g or placebo was given to 86 patients undergoing uterine curettage or gynaecological laparotomy 3 h before operation. The duration of anaesthesia in patients anaesthetized with thiopentone 7 mg kg-1 and premedicated with pethidine and atropine, was prolonged by 65% by probenecid 0.5 g, and by 46% by probenecid 1.0 g, compared with control (P < 0.05). In the absence of pethidine premedication, probenecid 0.5 g prolonged anaesthesia by 26% (P < 0.1). In patients without pethidine premedication anaesthetized with only thiopentone 4 mg kg-1 but who had no surgical stimulus during anaesthesia, probenecid increased the duration of the anaesthesia by 109% (P < 0.1). In this group the frequency of sleeping was 100%, as compared with 80% in the placebo-treated patients. Probenecid did not modify the response to pain and had no effect on apnoea, arterial pressure or heart rate.