Effects of aluminum magnesium hydroxide (A) and cimetidine (C) on the pharmacokinetics of minocycline (M) were investigated in female rats. Blood samples were collected at various time intervals until 36 hrs following oral dosing of drugs. Plasma minocycline concentrations were determined by HPLC. Control group (M), T₁ group (M+A), T₂ group (A+M after 2 hrs), T₃ group (M+A after 2 hrs), T₄ group (M+C) and T_5 group (C+M after 2 hrs) were divided to examine interaction of the drugs with minocycline. Plasma minocyline level-time curves were well described by two-compartment open model with first-order absorption in rats. Antacid treatment was associated with reduced of 71.0, 45.9, 35.7% in minocycline absorption rate constant(K_a), maximum plasma concentration(C_(max)), and relative bioavailability(F_(rel)), respectively. Cimetidine treatment group exhibited no significant changes in plasma level-time curve when compared with control group and did not affect minocycline absorption as by any of these three parameters.