Interaction between Ginkgo biloba and efavirenz
Data on interactions with antiretrovirals and herbal preparations are scarce and it can be difficult to predict whether there will be a clinical effect from in vitro studies.
This case report describes a possible interaction with efavirenz and Gingko biloba. The patient had been on an antiretroviral regimen of tenofovir/emtricitabine and efavirenz for two years and had achieved an undetectable viral load. However, virological failure developed and upon questioning it was found that the patient had been taking Gingko biloba for several months. Efavirenz concentrations were determined in stored plasma samples and showed decreasing concentrations that coincided with increasing viral load. The patient was successfully switched to alternative antiretrovirals.
Although the exact mechanism of the interaction remains unresolved, the authors propose that Gingko biloba extract (principally the terpenoids) may lower efavirenz plasma levels by the induction of CYP3A4 and P-gp.
Gingko biloba is a widely used herbal drug and is commonly used because of its assumed beneficial effects on concentration, memory, dementia and depressive disorders.
Source: www.hiv-druginteractions.org (June 2009)
Wiegman DJ et al. Interaction of Ginkgo biloba with efavirenz. AIDS, 2009,23(9): 1184-1185.