Pyrimethamine nanosuspension with improved bioavailability: in vivo pharmacokinetic studies

Pyrimethamine is a standard antiprotozoal drug recommended for prophylaxis and treatment of malarial infections. Limited bioavailability, slow onset of action, and life-threatening side effects restrict its use. Hence, in the present study, pyrimethamine nanosuspension was prepared with the objective to improve its dissolution rate and pharmacokinetic profile. Stable pyrimethamine nanosuspension with submicron particle size was prepared by nanoprecipitation and high-pressure homogenization techniques. Nanosizing and stabilizers modified the surface characteristics of drug particles resulting in considerable increase in the dissolution rate. The in vivo pharmacokinetic studies of the prepared nanosuspension were carried out and compared with plain pyrimethamine suspension and marketed pyrimethamine suspension. The in vivo pharmacokinetic profiling of pyrimethamine nanosuspension in rats showed higher AUC0-24 h and C max compared to the plain and marketed pyrimethamine suspensions. In contrast to its plain and marketed formulation, pyrimethamine nanosuspension showed rapid onset of action (T max 0.5 h vs. 2 h). Also, the low volume of distribution and reduced elimination half-life of the developed nanosuspension can lead to reduced side effects. Thus, improved in vitro-in vivo kinetics indicated that nanosuspension proved to be a suitable strategy for elevating the therapeutic profile of pyrimethamine.