Abstract An in vitro study of protein binding of metronidazole and mebendazole and their 1:1 mixtures with Cu(II) and Cr(III) have been carriedout by equilibrium dialysis method using spectrophotometer at 37± 0.5 ºC and at pH 7.4 and 2.4. It has been found that the interaction ofspecies with Cu(II) results into lowering the affinity and the percentage of protein binding of metronidazole to bovine serum albumin.On the other hand, interaction of Cu(II) with mebendazole increase the affinity and the percentage of protein binding of mebendazole tobovine serum albumin. But the interaction with Cr(III) has very little impact on protein binding of metronidazole and mebendazole. Thevalues for the affinity constants, number of binding sites and the nature of protein binding curves have been investigated for thesespecies. Careful consideration is needed during concurrent administration of metronidazole or mebendazole with Cu (II) and Cr (III). [avf_view name="Article Addons" view-id="66d98451c48e3"]