Some examples of interactions between drugs in cancer chemotherapy

Drug combinations in cancer treatment are widely utilized because they frequently result in better therapeutic activity than the single treatments. The mechanism(s) by which this can be achieved may reside in an enhanced chemotherapeutic effect or in reduced toxicity, it being difficult to dissociate the two aspects. To underline this difficulty, experimental studies will be reported. A first example illustrates the interaction between phenobarbital and cyclophosphamide. Depending on the schedule of administration, different effects can be obtained. These effects cannot always be explained by pharmacokinetic data. A second example deals with the combination of anthracycline antibiotics (daunomycin and adriamycin) with immunostimulant treatment (C. parvum). Both in vitro and in vivo adriamycin was less toxic than daunomycin for macrophages. As predicted on the basis of this finding, adriamycin resulted in a synergistic antitumoral effect when combined with macrophage activators.