Effect of Oral Administration of Crude Aqueous Extract of Garlic on Pharmacokinetic Parameters of Isoniazid and Rifampicin in Rabbits

AIM: To study the effect of oral administration of crude aqueous extract of garlic for 14 days on pharmacokinetic parameters of isoniazid and rifampicin. MATERIALS AND METHODS: Crude extract was prepared according to the method described by Fromtling and Bulmer. The study was done on 16 New Zealand white rabbits, divided into two groups of 8 animals each for two drugs. Baseline pharmacokinetic parameters for single-dose isoniazid and rifampicin were calculated from plasma drug concentrations obtained at various time intervals after dosing. The animals were given garlic extract orally for 14 days. Pharmacokinetic parameters were calculated again as done previously. OBSERVATIONS: Administration of crude aqueous extract of garlic significantly altered the pharmacokinetic parameters for isoniazid. C(max) was reduced from 15.4 +/- 5.6 to 5.4 +/- 3.3 microg/ml. AUC((0-24)) was reduced from 76.7 +/- 25.0 to 34.3 +/- 19.2 microg/ml.h. No significant change in T(max), k(el) and AUC((0-)(alpha)) was seen. Pharmacokinetic parameters of rifampicin were not significantly altered by administration of garlic extract. CONCLUSIONS: Oral administration of garlic extract decreased the bioavailability of isoniazid significantly with no change in rate of elimination. Bioavailability of rifampicin is not significantly altered by garlic extract.