Three-dimensional analysis of the synergistic cytotoxicity of ganciclovir and zidovudine.

The combined cytotoxicity of zidovudine and ganciclovir in three cell lines of human origin was examined. The data were generated by a new rapid cell proliferation assay and a more sensitive plating efficiency assay. A three-dimensional analytical approach was used to evaluate the drug-drug interactions, and the results were compared with those obtained by two conventional methods of analysis. Synergistic cytotoxicity was observed in all cell lines examined and by both assays. Moreover, this synergistic cytotoxicity was statistically significant at physiologically relevant concentrations. It is not known whether these drug-drug interactions manifest themselves in vivo as granulocytopenia or other untoward side effects. These results, however, indicate that further investigation is warranted and that the coadministration of zidovudine and ganciclovir may be contraindicated.