Pharmacokinetic and clinical study of ropivacaine and bupivacaine in women receiving extradural analgesia in labour.

Abstract

We have compared, in a randomized, double-blind study, the pharmacokinetics of ropivacaine and bupivacaine during labour. Total and free plasma concentrations of ropivacaine and bupivacaine were measured after the first of two extradural doses. The main dose was 20 mg (test dose) and 30 mg, with a top-up dose of 25 mg when requested. After the main dose, Cpmax (total) of ropivacaine (0.50 mg litre-1) was similar to that of bupivacaine (0.48 mg litre-1). At 20 min, Cpmax (free) of ropivacaine (0.04 mg litre-1) was higher than that of bupivacaine (0.02 mg litre-1) (P = 0.0025). The clinical effectiveness of the block was similar in both groups.