Pharmacokinetics and Biodistribution of Anastrozole in a Polymer-Containing Formulation

A polymer-containing anastrozole formulation (PAF) in the form of micronized particles based on a copolymer of lactic and glycolic acids with a terminal carboxyl group (PLGA-COOH 50/50) was prepared. The pharmacokinetics and biodistribution of anastrozole in the organs of rats after single intramuscular (i.m.) doses of PAF and anastrozole substance 6.8 mg/kg (in terms of active substance) were studied. The pharmacokinetics of anastrozole were found to be linear over the range 1.7 – 6.8 mg/kg, in terms of AUC(0 – 336) (R2 = 0.99989) and Cmax (R2 = 0.99767) after i.m. administration of the PAF developed here to rats. Use of PAF was found to slow the absorption and elimination of anastrozole in the blood, liver, kidneys, bone, adrenals, fatty tissue, and muscles in rats, as evidenced by increases in the T1/2 and MRT and decreases in Cl, Kel, and Cmax/AUC(0 – 336). Tissue availability of anastrozole (fT) in the adrenals, fatty tissue, and muscles of rats after administration as PAF was 1.12, 1.44, and 1.37 times higher respectively than after administration of anastrozole substance.