Effect of intravenous cimetidine on lignocaine disposition during extradural caesarean section

We studied whether an intravenous bolus of cimetidine altered the disposition of extradurally administered lignocaine in the parturient. Mothers who requested extradural analgesia for elective Caesarean section were randomly pretreated with either cimetidine 200 mg intravenously (n = 5) or no H2-receptor antagonist (n = 5). No difference was found between peak plasma lignocaine levels or area under the plasma concentration/time curve between the two groups after administration of 6 mg/kg lignocaine 2% with adrenaline 1:200,000. There was no evidence for an effect of a single intravenous dose of cimetidine on lignocaine disposition in the obstetric patient. In addition, the extradural administration of 6 mg/kg lignocaine produces plasma levels well below toxic levels.