No Interaction Expected
Quality of Evidence: Very Low
Coadministration of tenofovir-DF and ethambutol alone has not been studied but based on metabolism and clearance a clinically significant interaction is unlikely. Ethambutol is partly metabolized by alcohol dehydrogenase (20%) and partly eliminated unchanged in the faeces (20%) and in the urine (50%). Coadministration of TB treatment containing ethambutol (with rifampicin, isoniazid and pyrazinamide) and tenofovir-DF (with emtricitabine and efavirenz) increased tenofovir AUC and Cmin by 13% and 9% and decreased Cmax by 2%; there was no effect on ethambutol concentrations.