Inhibitory effect of clemastine on P-glycoprotein expression and function: an in vitro and in situ study

Abstract

<strong><em>Objective(s):</em></strong>Transporters have an important role in pharmacokinetics of drugs. Inhibition or induction of drug transporters activity can affect drug absorption, safety, and efficacy. P-glycoprotein (P-gp) is the most important membrane transporter that is responsible for active efflux of drugs. It is important to understand which drugs are substrates, inhibitors, or inducers of P-gp to minimize or avoid unwanted interactions. The aim of this study was to investigate the effects of clemastine on the expression and function of P-gp. <strong><em>Materials and Methods: </em></strong>The effect of clemastine on P-gp function and expression was evaluated <em>in vitro</em> byrhodamine-123 (Rho₁₂₃) efflux assay in Caco-2 cells and Western blot analysis. Rat <em>in situ</em> single pass intestinal permeability model was used to investigate the clemastine effect on digoxin P_eff, as a known P-gp substrate. Digoxin levels in intestinal perfusates were assayed by high performance liquid chromatography (HPLC) method. <strong><em>Results:</em></strong>The Caco-2 intracellular accumulation of Rho₁₂₃ in clemastine and verapamil treated cells was 90.8 ± 9.8 and 420.6±25.4 pg/mg protein, respectively which was significantly higher than that in control cells (50.2±6.0; <em>P</em><0.05). Immunoblotting results indicated that clemastine decreased expression of P-gp in Caco-2 cells <em>in vitro</em>. More over effective intestinal permeability (P_eff) of digoxin in the presence of clemastine, was significantly increased compare to control group. <strong><em>Conclusion: </em></strong>Findings of our study suggested dose dependent P-gp inhibition activity for clemastine <em>in vitro</em> and <em>in situ</em>. Therefore co-administration of clemastine with P-gp substrates may result in unwanted interactions and side effects.