VINBLASTINE AND ERYTHROMYCIN - AN UNRECOGNIZED SERIOUS DRUG-INTERACTION

Vinblastine and erythromycin are among the most commonly used chemothe rapeutic and antimicrobial agents, respectively. No interaction betwee n the two has ever been reported. Towards the end of a phase I study o f vinblastine plus oral cyclosporin (to reverse multidrug resistance), three patients also received erythromycin to raise their cyclosporin levels. All developed severe toxicity consistent with a much higher vi nblastine dose than was actually given. This apparent potentiation of vinblastine toxicity has not been previously described.