Fanconi syndrome caused by low-dose adefovir dipivoxil

Area of Science:

• Nephrology
• Hepatology
• Pharmacology

Background:

• Adefovir dipivoxil (ADV) is an antiviral medication used for chronic hepatitis B.
• Low-dose ADV (10 mg daily) was previously considered to have a low risk of nephrotoxicity.
• Acquired Fanconi syndrome (FS) is a generalized proximal tubule dysfunction.

Observation:

• Three patients (one woman, two men) of Asian ethnicity developed acquired Fanconi syndrome (FS) while on low-dose ADV therapy.
• Symptoms included bone pain and muscle weakness.
• Diagnosis was confirmed by electrolyte and phosphate imbalances.

Findings:

• Patients experienced normalization of serum phosphate after switching from ADV to entecavir, with or without phosphate supplementation.
• One patient did not show significant improvement after switching to tenofovir, despite phosphate supplementation.
• Low-dose ADV-induced FS appears to be more prevalent in the Asian population.

Implications:

• Regular monitoring of urine and serum phosphate is essential for patients on ADV therapy.
• Entecavir may be a more suitable alternative to ADV than tenofovir for patients developing FS.
• This study highlights a previously underestimated risk associated with low-dose ADV, necessitating vigilant patient management.