TDF Nephrotoxicity — RACP Adult Medicine MCQ

Instant feedback + full explanation. One question, done properly.

ModerateClinical PharmacologyTDF NephrotoxicityRACP Adult Medicine

A 45-year-old man with chronic hepatitis B on tenofovir disoproxil fumarate (TDF) for 5 years develops progressive renal impairment (eGFR declining from 90 to 55 mL/min/1.73 m²) and hypophosphataemia. What is the most likely cause?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: B — ACE inhibitor effect

Tenofovir disoproxil fumarate (TDF) can cause proximal renal tubular dysfunction resembling Fanconi syndrome (phosphaturia, glucosuria, aminoaciduria, type 2 RTA with metabolic acidosis). This leads to hypophosphataemia and progressive CKD. Risk factors include pre-existing CKD, diabetes, and concomitant nephrotoxic drugs. Management is to switch to tenofovir alafenamide (TAF) – a prodrug with significantly less renal and bone toxicity – or to entecavir. Renal function typically stabilises or improves after switching. Regular renal monitoring (eGFR, phosphate, urinalysis) is recommended on TDF.

Reference: AMH – 2025 – Tenofovir; eTG – 2025 – Antibiotic Guidelines