A rapid and sensitive high performance liquid chromatographic assay of the new antimalarial compound 80/53 in serum with a novel sample clean-up method and its pharmacokinetics in rabbits.

The compound 80/53 (AM) is a new antimalarial agent synthesized by this institute as a safer and less toxic analogue of primaquine. It was found to exhibit fluorescence in acetonitrile solution and this finding was exploited to develop a selective and sensitive high performance liquid chromatographic (HPLC) assay of the AM in rabbit serum. The sample clean-up was done in a single step by simultaneous protein precipitation and extraction with acetonitrile in the presence of sodium sulfate. The lower limit of quantitation of the method was 50 ng ml-1 using 100 microliters of serum sample. The method was fully validated from 50 to 1600 ng ml-1 concentration range with a recovery ranging from 70 to 75%. The within- and between-run variability was less than 10% and the drug in serum was stable over four freeze-thaw cycles and up to 24 h in injection solvent at 4 degrees C. The method was applied to determine the pharmacokinetic parameters of AM in 5 rabbits receiving a single bolus intravenous and peroral dose in a crossover study. The concentration-time data after a 5 mg kg-1 i.v. dose in rabbits was best fitted to the two compartment body model with first order absorption and elimination rate constants. The terminal half-life and MRT of AM were 95.3 +/- 43.5 and 104 +/- 10.6 min respectively. After administering a single 20 mg kg-1 oral dose, the serum levels of AM in all the rabbits declined below the quantitation limit by 90 min and it was not possible to fit the data by the compartmental approach. The MRT and AM after oral dose was 31.1+2-8.3 min. Application of the assay has also been extended to analyze the serum samples of rats, monkeys and humans.