Utility of Therapeutic Drug Monitoring in Identifying Clinically Significant Interactions Between St. John's Wort and Prescription Drugs

Abstract

Background:The general population widely uses herbal medicines, as they are regarded as effective and safe. St. John's wort, which is an effective herbal antidepressant, exhibits both pharmacokinetic and pharmacodynamic interactions with several drugs. The aim of this review was to highlight the clinically significant interactions of St. John's wort with drugs that require to be monitored to assess their therapeutic effect.Methods: Published literature was searched using electronic databases, such as MEDLINE, PubMed, and Elsevier ScienceDirect using terms such as "herbal medicine," "herbal toxicity," "legislation herbal medicine," "drug-herb interactions," "St. John's wort," and "St. John's wort-drug interactions." Searches were limited to the English language, and there was no restriction on the date of publication.Results: St. John's wort exhibits a number of pharmacokinetic and pharmacodynamic interactions with drugs. The most dangerous interactions occurred when used concurrently with the immunosuppressants, cyclosporine, and tacrolimus (treatment failure or organ rejection) or warfarin (treatment failure resulting in thromboembolic events) or antiretroviral agents (treatment failure and the emergence of new viral variants that are resistant to conventional drugs).Conclusions: Patients should consult their health care providers before consuming herbal supplements, especially St. John's wort, to avoid potentially dangerous drug-herb interactions.

Impact of Cytochrome P450 Enzymes on the Phase I Metabolism of Drugs

“…Moreover, metabolic reactions may be often directly related to food, with some foods exerting their activity by interacting with CYPs. For instance, St. John's wort deeply induces CYP3A4 [12] and, therefore, it lowers drug bioavailability and exposure. Pomegranate (Punica granatum L.) juice, grapefruit and cranberries effectively inhibit both CYP3A4 and/or CYP2C9 [13][14][15].…”

The effect of consumption of Mangifera indica (Linn) fruit on the plasma concentration profile of zidovudine, lamivudine and nevirapine

“…Recent evidence has also documented the interaction between St. John's wort and certain antiretroviral drugs. St. John's wort was found to reduce plasma level of indinavir and that of preparation of lopinavir/ritonavir [5,6]. Food/fruit-drug interactions can result in two main clinical effects; decreased bioavailability of a drug which predisposes to treatment failure or an increased bioavailability which increases the risk of adverse events which may sometimes be life threatening [4].…”