Renal tubular dysfunction during long-term adefovir or tenofovir therapy in chronic hepatitis B

Background Adefovir and tenofovir are nucleotide analogues used as long-term therapy of chronic hepatitis B. Side effects are few, but prolonged and high-dose therapy has been associated with proximal renal tubular dysfunction (RTD). Aim To assess the incidence of RTD during long-term nucleotide therapy of chronic hepatitis B. Methods A total of 51 patients being treated at the Clinical Center, National Institutes of Health were studied. Diagnosis of RTD required de novo appearance of at least three of five features: hypophosphataemia, hypouricaemia, serum creatinine elevation, proteinuria or glucosuria. Results Among 51 patients treated for 110 (mean 7.4) years with adefovir (n = 42), tenofovir (n = 4) or adefovir followed by tenofovir (n = 5), 7 (14%) developed RTD. Time to onset ranged from 22 to 94 (mean 49) months with an estimated 10-year cumulative rate of 15%. All seven had low urinary percent maximal tubular reabsorption of phosphate (<82%). Patients with RTD were older (58 vs. 44 years; P = 0.01) and had lower baseline glomerular filtration rates (82 vs. 97 cc/min; P = 0.08) compared to those without; but did not differ in other features. Six patients with RTD were switched to entecavir, all subsequently had improvements in serum phosphate (2.03.0 mg/dL), creatinine (1.61.1 mg/dL), uric acid (2.73.8 mg/dL) and proteinuria. Conclusions Renal tubular dysfunction develops in 15% of patients treated with adefovir or tenofovir for 29 years and is partially reversible with change to other antivirals. Monitoring for serum phosphate, creatinine and urinalysis is prudent during long-term adefovir and tenofovir therapy.