Nephrotoxicity Associated with Concomitant Use of Ledipasvir-Sofosbuvir and Tenofovir in a Patient with Hepatitis C Virus and Human Immunodeficiency Virus Coinfection

Direct-acting antivirals (DAAs) have revolutionized the treatment of hepatitis C virus (HCV) infection, with superior efficacy and safety compared to interferon-based therapies. Despite these improvements, drug interactions with DAAs exist and may be clinically relevant in human immunodeficiency virus (HIV)-coinfected patients. We present a case of nephrotoxicity associated with concomitant use of tenofovir disoproxil fumarate (TDF) and ledipasvir-sofosbuvir (LDV-SOF). A 56-year-old woman with HIV infection who had been taking efavirenz/tenofovir/emtricitabine (EFV/TDF/FTC) for 6 years developed acute kidney injury 8 weeks after initiating LDV-SOF for the treatment of HCV infection. Her serum creatinine concentration peaked at 10 mg/dL, compared with her baseline concentration of 0.91 mg/dL. Kidney biopsy revealed acute tubular necrosis and acute interstitial nephritis. Both LDV-SOF and TDF were discontinued, and the patient's serum creatinine concentration decreased to 1.3 mg/dL over the following 6 weeks. We postulate that this adverse drug reaction may have been secondary to the known interaction between ledipasvir and TDF, which results in increased TDF exposure. Despite knowledge of this interaction, LDV-SOF is commonly prescribed in patients with HIV-HCV co-infection, as patients who received LDV-SOF-and TDF-containing regimens in trials have not demonstrated adverse clinical consequences related to this interaction. This case highlights the rare but potentially serious nephrotoxicity that can result from TDF toxicity and serves as a reminder to clinicians to implement close renal function monitoring in patients receiving both LDV-SOF and TDF. Clinicians prescribing LDV-SOF to HCV-HIV-coinfected patients receiving TDF should be cautious about use with concomitant nephrotoxic medications and monitor markers of tubular dysfunction, including urinary phosphorus excretion, and renal injury at baseline and week 4 of therapy. Tenofovir alafenamide and alternative DAAs may also have a role in the management of patients at high risk for renal adverse effects from TDF.