Elimination of pethidine and bupivacaine in the newborn.

Pethidine or an epidural injection of bupivacaine are common forms of obstetric analgesia in Britain. Bupivacaine has been thought to have little effect on the fetus, but neurobehavioural studies have cast doubt on this. We therefore investigated the elimination of these drugs by babies in similar population groups. Bupivacaine was largely eliminated in just over one day, while pethidine required between 2 and 6 days. This could account for the persisting depression in babies whose mothers had received pethidine.