OBJECTIVES: Few data are available from prospective trials to define the hepatotoxicity of diclofenac, the most widely prescribed non-steroidal anti-inflammatory drug (NSAID) in the world. We determined the rate of laboratory and clinical adverse hepatic effects in a large double-blind trial of diclofenac.

METHODS: Patients ≥50years with rheumatoid arthritis or osteoarthritis were randomly assigned to diclofenac (150 mg daily) or etoricoxib (60 or 90 mg daily). Patients with hepatic disease or who reported ≥ 14 alcoholic drinks weekly were excluded. Patients had visits (with liver tests) every 4 months and were contacted by phone between visits and every 6 months after discontinuation until the end of the study. Causality assessment was performed for liver-related hospitalizations, Hy's cases (serious adverse events with AST or ALT >3× upper limit of normal (ULN) and bilirubin >2×ULN), and liver failure/transplant/death.

RESULTS: A total of 17,289 patients received diclofenac for a mean of 18 months. Liver end points with diclofenac were ALT/AST>3×ULN: 527(3.1%); ALT/AST>10×ULN: 86(0.5%); liver-related hospitalizations: 4(0.023%); Hy's cases: 2(0.012%); liver failure/death/transplant: 0. Aminotransferase elevations occurred primarily within the first 4-6 months of therapy, whereas liver-related hospitalizations occurred between 9 days and 21 months.

CONCLUSIONS: Diclofenac is commonly associated with aminotransferase elevations, generally in the first 4-6 months of therapy. Clinical liver events requiring hospitalization are relatively rare (23/100,000 patients), but may develop early or late in therapy. The markedly increased rate of aminotransferase elevation with diclofenac may not be paralleled by a proportional marked increase in clinical liver events, although clinical events potentially also may be decreased with regular monitoring in a clinical trial setting.

Am J Gastroenterol 2009; 104:356-362; doi:10.1038/ajg.2008.149; published online 27 January 2009