Ocular toxicity associated with Ethambutol in the South-East Asia Region

Ethambutol-induced optic neuropathy is a well-documented adverse reaction, the severity of which depends on drug serum concentration in the body. The recent dose-frequency modification for ethambutol from thrice-weekly regimen to daily-dose regimen might have opened doors for increased drug toxicity, resulting in increasing incidence of ocular toxicity.

A retrospective, post-market observational study was conducted using data collected from VigiBase® until Jan 2026, using mapped terms under Medical Dictionary for Regulatory Activities (MedDRA).

Of 49,327 ethambutol-suspected adverse event cases reported globally, 4,748 cases were reported under the system organ class (SOC) eye disorders, of which 220 blindness cases were reported globally. Within South-East Asia Region (SEAR), India (n = 820, 79.8%), Thailand (n = 148, 14.4%) and Indonesia (n = 59, 5.7%) reported cases of ethambutol-related eye disorders. Commonly reported preferred terms in SEAR include vision blurred (n = 425, 41.3%), visual impairment (n = 263, 25.6%), optic neuropathy (n = 68, 6.6%), blindness (n = 66, 6.4%) and eye pain (n = 20, 1.9%), with more cases being observed in adults within the age group of 18-64 years. India alone reported 65 cases of blindness followed by Indonesia with 1 case reported.

The increased cases of ethambutol-related ocular toxicity specifically blindness warrants periodic monitoring, dose adjustments and exploring newer, safer antibiotics.