Tenofovir induced Fanconi syndrome: a possible pharmacokinetic interaction

Tenofovir was introduced as a second line drug for the treatment of human immunodeficiency virus (HIV) infection in India in December 2009. Although rare, renal toxicity is a recognized adverse drug reaction (ADR) of this drug, especially when administered with boosted lopinavir-ritonavir. In this case, an HIV positive patient receiving tenofovir based antiretroviral therapy (ART) for last 1 year developed albuminuria, glycosuria and hypophosphatemia. Renal function tests and random blood sugar were within normal limits. He was diagnosed as a case of tenofovir induced Fanconi syndrome. Tenofovir was discontinued and patient was prescribed an alternate regimen. Five months later clinical symptoms and renal functions returned to normal. A pharmacokinetic interaction between tenofovir and ritonavir may have resulted in the toxicity. A periodic monitoring of renal functions is desirable in patients on tenofovir based ART.