Psychosis resulting from trimethoprim-sulfamethoxazole treatment for preseptal cellulitis.

Trimethoprim-sulfamethoxazole (TMP-SMX) is a commonly used antimicrobial agent because of its low cost, diverse antimicrobial profile, and minimal severe adverse effects. A rare side effect is psychosis, a complication that has not been published in the ophthalmology literature. A 53-year-old female presented to the ophthalmology office with left upper eyelid erythema, focal tenderness, and discharge.