Inhibition by an unrelated drug …
In order to reverse the typical MDR phenotype ...discovery of the very efficient hemosensitizing activity of the semi-synthetic antibiotic tiamulin, which overpasses the capacities of reference products such as verapamil and cyclosporin-A in terms of in vitro reversal effect.
In Vitro and In Vivo Reversal of Cancer Cell Multidrug Resistance by the Semi-synthetic Antibiotic Tiamulin. L.G. Baggetto, M. Dong, J. Bernaud, L. Espinosa, D. Rigal, R., & E. Marthinet. Biochem. Pharmacol (1998) 56 1219-1228.