The pharmacokinetic profile of orally administered oxytetracycline (10 mg/kg body weight)was studied 7 days post oral treatment of Piper longum (15 mg equivalent/kg) in White Leghorn hens (2-2. 8 kg). On the day 8, oxytetracycline (OTC)was administered orally and blood samples were collected from the wing vein in heparinised vials for plasma separation at 0 (pre-treatment), 15, 30, 60, 120, 240, 360, 480 and 600 minutes post OTC administration. Plasma OTC concentrations were determined by microbial assay technique using Bacillus cereus var. mycoides (ATCC 11778)as test organism. The plasma levels of OTC against time were adequately described by one compartment open model. The pharmacokinetic data revealed that P. longum treated animals had significantly higher area under curve (AUC), area under the first moment of plasma drug concentration-time curve (AUMC)and mean residential time (MRT). Prior treatment of P. longum significantly reduced elimination rate constant (beta)and increased elimination half life (t1/2beta ). The total body clearance (Cl B ) reduced by 21%whereas total duration of pharmacological effect (t d )increased by 29%. The treatment with P. longum reduced loading and maintenance dose by 33. 3 and 39%, respectively.