A COMPARISON OF THE POTENTIAL TOXICITY OF BUPIVACAINE, LIGNOCAINE AND MEPIVACAINE DURING EPIDURAL BLOCKADE FOR SURGERY

Bupivacaine 0.5 per cent with adrenaline 5 μg/ml was given to ten patients, and a combination of bupivacaine, lignocaine and mepivacaine (0.25 per cent of each) to four patients, to provide epidural blockade for surgery, and the blood concentrations of local analgesics were measured by gas chromatography. When comparing different drugs, both given individually (and the results expressed as a function of dosage) and given in an equal dose mixture, bupivacaine consistently produced the lowest blood concentrations and mepivacaine the highest. If clinically occurring blood concentrations are compared with those associated with toxic symptoms during intravenous infusion in man, the margin of safety appears wider with bupivacaine than with lignocaine or mepivacaine.