Pharmacokinetic and pharmacodynamic studies of magnolol after oral administration in rats

Little is known about the pharmacokinetics and pharmacodynamics of magnolol despite numerous pharmacological investigations. Hence the present study which aimed to examine the pharmacokinetics of magnolol after its oral administration in rats, and to determine its pharmacodynamic properties with regard to its effect on locomotor activity. The absorption half-life, the elimination half-life, the time of maximum concentration and the maximum concentration were found to be 0·63 h, 2·33 h, 1·12 h and 0·16 μg mL−1, respectively. Oral bioavailability was about 4·9%. Oral administration of higher doses of magnolol (20, 50 and 100 mg kg−1), but not lower doses (5 or 10 mg kg−1), significantly suppressed the locomotor activity of the animal. A first order one-compartment model was proposed after oral administration of magnolol (20 mg kg−1). For reduction of locomotor activity, the minimum effective oral dose was 20 mg kg−1, with a minimum effective plasma concentration of 0·1 μg mL−1.