Aims: Considering the well known biological effects of secretion of cutaneous glands in anurans and that Pdr5p belongs to the ATB-Binding Cassette (ABC) superfamily of membrane transporters, which efflux a large variety of xenobiotic compounds, and play an important role in the multidrug resistance (MDR), the parotoid gland of two bufonids were used in order to evaluate their secretion activity on Pdr5p of plasma membranes of the yeast Saccharomyces cerevisiae as a potential inhibitor of MDR.