Abstract
The treatment with H2-receptor blockers as a prophylactic antacid for premedication of anesthesia has been widely employed. Cimetidine is known to inhibit clearance of many drugs including local anesthetics by reducing hepatic blood flow and/or by inhibiting cytochrome P-450 enzymes. However, it is said that famotidine, a newly synthesized cimetidine analogue, does not inhibit enzyme activities. Bupivacaine is widely used as a local anesthetics for epidural anesthesia. However it remains unknown whether famotidine has an adverse effects on kinetics of this local anesthetics. Therefore a principal purpose of this study was to investigate whether a bolus administration with famotidine before epidural anesthesia altered the plasma levels of bupivacaine in comparisons with effects of cimetidine on the kinetics of this local anesthetics. Twenty-four patients, who were scheduled to undergo abdominal surgery by epidural anesthesia with 0.5% bupivacaine 10ml, were randomly divided into three groups.: One hour before the operations, the first and second eight patients received either cimetidine (200mg diluted up 20ml with normal saline, IV) or famotidine (20mg dissolved in normal saline 20ml, IV) respectively, while other eight control patients received only normal saline 20ml (IV). Plasma concentration of bupivacaine was determined by gas chromatography. No significant differences in plasma bupivacaine levels was found at any time among three groups. Thus the results suggest that famotidine, likewise cimetidine, does not significantly affect bupivacaine levels when given 1hr before anesthesia.
