Pharmacokinetics of mequindox and its metabolites in rats after intravenous and oral administration

Pharmacokinetics of mequindox (MEQ) and its metabolites were determined in rats after intravenous (i.v.) and oral (p.o.) administration of MEQ at a single dose of 10 mg kg⁻¹ bodyweight. After both administrations, MEQ and five of its metabolites were quantified, except M4, whereas M1 and M2 were the predominant ones. The areas under the concentration–time curves (h ng mL⁻¹) of MEQ, M1, M2, M3, M5 and M10 after i.v. administration were 7559 ± 495, 6354 ± 2761, 5586 ± 2337, 1034 ± 160, 2370 ± 791 and 1813 ± 622, respectively, whereas after p.o. administration, remained as 2809 ± 40, 4361 ± 3544, 4351 ± 1046, 1444 ± 814, 3864 ± 305 and 1213 ± 569, respectively. The elimination half-lives (h) of these compounds after i.v. administration were 3.48 ± 0.80, 4.20 ± 0.76, 6.25 ± 2.41, 4.77 ± 1.54, 4.69 ± 1.62 and 16.89 ± 5.15, respectively, and were 3.21 ± 0.40, 3.66 ± 1.06, 4.20 ± 1.03, 8.91 ± 5.99, 4.20 ± 2.02 and 20.84 ± 10.85 after p.o. administration, respectively. After p.o. administration, the bioavailability of MEQ was 37.16%. The results showed that MEQ was extensively metabolized in rats and rapidly absorbed after p.o. administration.