Herb - drug interaction of noni juice and Ginkgo biloba with phenytoin

The common perception regarding the herbal medicines is that they are natural and safe. Although considered natural, most of the herbal medicine can interact with other drugs causing either potentially dangerous side effects or they can lead to loss or decreased therapeutic benefits of the drugs. Currently, there is growing concern to analyse and understand the herb - drug interactions. This study investigates effects of noni juice/Ginkgo biloba on the pharmacokinetics of phenytoin and also on the oxidative stress associated with long term administration of phenytoin. After pretreatment for 7 days with noni juice and G. biloba, on day 8 the phenytoin was co-administered orally with noni juice and G. biloba and the serum pharmacokinetics were determined at various time points (1, 2, 4,6, 8,12 and 24 h) by HPLC. The oxidative stress markers were determined after 30 days of treatment. Noni juice pretreated rats decreased the bioavailability of phenytoin by 2.81 fold, whereas G. biloba pretreated rats increased the bioavailability by 2.08 fold when compared with control. Noni juice and G. biloba treated rats provided significant protective effect against the oxidative stress induced by long term administration of phenytoin. It is observed that noni juice and G. biloba might have altered the bioavailability of phenytoin due to induction and inhibition of CYP2C9 enzymes.