The single oral dose pharmacokinetics of chloroquine (5mg/kg body weight) and metronidazole (7.5mg/kg body weight) were studied in rats' serum. Chloroquine and metronidazole concentrations were measured using highperformance liquid chromatography (HPLC) method developed earlier in our laboratory. The data were fitted into a WinNonlin standard non-compartmental programme. The Maximum serum concentration Cmax (µg/ml) of chloroquine was 5.70 ± 1.41 while that of metronidazole was 3.13  0.30, Time

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... to peak concentration tmax was 1.00  0.00 (h) and that of metronidazole was 0.83 ± 0.27, Volume of distribution Vd (L) 1.33 ± 0.26 for metronidazole 2.39  0.28; Elimination half-life t1/2 (h) 10.05 ± 3.01 for metronidazole 4.05  0.46. The values were comparable with the works of other authors. Compounds that show very high activity in -vitro may not have in vivo activity, or may be highly toxic using in-vivo models due to undesirable pharmacokinetic properties, and toxicity may result from formation of reactive metabolites. This study assures the quality of the brands of the drugs and encouraged the use of animal model in determining pharmacokinetic properties especially in drug design.