Two Cases of Hypophosphatemic Osteomalacia After Long-term Low Dose Adefovir Therapy in Chronic Hepatitis B and Literature Review

Adefovir dipivoxil (ADV) is a nucleotide used as long-term therapy of chronic hepatitis B. Many published reports have shown that long-term high-dose therapy with adefovir can be associated with proximal renal tubular dysfunction resulting in significant hypophosphatemia, renal insufficiency and osteomalacia. We have encountered two patients who developed evidence of hypophosphatemic osteomalacia while on long-term low-dose adefovir therapy for chronic hepatitis B. We report on its clinical features and its potential resolution with cessation of the drug and supplementation with phosphate. We also reviewed the other published cases associated with hypophosphatemic osteomalacia after low-dose adefovir therapy. The symptoms and the hypophosphatemia improved after cessation of the drug and supplementation with phosphate in most cases. Patients taking adefovir long-term should receive regular investigation of the phosphate level and renal function.