Real-world safety and effectiveness of intravenous fomepizole in patients with ethylene glycol and methanol poisoning in Japan: results of a 7-year post-marketing surveillance study

Background Fomepizole is a competitive alcohol dehydrogenase inhibitor used for the treatment of ethylene glycol and methanol poisoning. We evaluated the safety and effectiveness of fomepizole in patients with ethylene glycol or methanol poisoning in Japan. Research design and methods This retrospective post-marketing surveillance study conducted in Japan registered patients who received fomepizole intravenous infusion per the package insert (January 2015-June 2022). Endpoints included adverse drug reactions/infections (ADRs), arterial blood pH, and treatment outcomes. Results Of 147 patients registered (91 institutions), 131 and 126 were included in the safety and effectiveness analysis sets, respectively. Mean age was 43.6 years, and 66.4% were male. Mean time from poison ingestion to treatment was 15.1 hours; 66.4% received concomitant hemodialysis. No serious ADRs were reported. ADRs were reported in seven patients; the most-reported ADR was vomiting (2.3%). Seven patients died, 105 survived without sequelae, and 19 survived with sequelae. Most common sequelae were renal failure or renal dysfunction. Mean arterial blood pH increased to 7.4 by 4 hours of treatment, remaining stable for 24 hours post-treatment. Conclusions Fomepizole is well tolerated and helps improve clinical outcomes in patients with ethylene glycol or methanol poisoning in Japan.