Analysis and pharmacokinetics of bulaquine and its major metabolite primaquine in rabbits using an LC-UV method— a pilot study

Lal, Jawahar
Mehrotra, Nitin
Gupta, Ram Chandra

Pharmacokinetics and Metabolism Division, Central Drug Research Institute, Chattar Manzil Palace, P.O. Box 173, Lucknow 226001, India

^*Corresponding author. Tel.: +91-522-2212414-4377; fax: +91-522-2223405/2223938

Received 13 November 2002; received in revised form 16 January 162003; accepted 17 January 2003.

☆ CDRI Communication No.: 6349.

Journal of Pharmaceutical and Biomedical Analysis 32(1):p 141-150, April 2003. | DOI: 10.1016/S0731-7085(03)00033-5

Abstract

A precise and reproducible HPLC assay has been developed and validated for simultaneous determination of bulaquine (BQ) and its metabolite primaquine (PQ) in rabbit plasma. The method, applicable to 0.5 ml plasma, involves double extraction of samples with n-hexane: isopropanol (98:2, v/v) containing dimethyl octylamine (DMOA) (0.1%, v/v). Separations were accomplished by reversed-phase liquid chromatography using a Spheri-5 cyano column with a low pressure gradient with mobile phase consisting of ammonium acetate buffer (50 mM, pH 6.0) and acetonitrile with DMOA. The method was sensitive with a limit of quantitation of 20 ng ml⁻¹ in rabbit plasma for both BQ and PQ and the recoveries were >85 and >45%, respectively. Excellent linear relationships (r>0.99) were obtained between the measured and added concentration ratios of the plasma concentrations over a range of 20–1000 ng ml⁻¹ for both the analytes. Precision and accuracy were acceptable as indicated by relative standard deviations from 1.8 to 15.1%, bias values ranging from −14.2 to 15.7%. Moreover, BQ was stable in rabbit plasma for 15 days of storage at −60 °C and after being subjected to three freeze-thaw cycles. The method was applied to determine the levels and pharmacokinetics of BQ in rabbits following a single 2.5 mg kg⁻¹ oral and intravenous dose. The BQ levels declined and the PQ levels increased with time. The PQ/BQ ratio after oral dose at 1 and 1.5 h were higher than that after intravenous dose. In the pilot preclinical pharmacokinetic study after a single 2.5 mg kg⁻¹ oral dose, BQ levels were determined up to 6 h (post-prandial) and 8 h (fasting). The plasma concentration versus time data were best fitted to a two-compartment open model with first-order absorption and elimination processes without lag time. The AUC_0–∞ and the elimination Symbol in fasted rabbit was higher than that in post-prandial rabbit indicating the effect of food on BQ pharmacokinetics.