Aim and background: To report a case of bilateral acute angle closure glaucoma following phentermine monotherapy after prior topiramate discontinuation, highlighting the ocular risks of widely used weight loss medications, whether prescribed alone or in combination.Topiramate has a well-established role in acute bilateral angle closure glaucoma through ciliochoroidal permeability changes and choroidal effusion, while phentermine is contraindicated in glaucoma and has been implicated in bilateral angle closure glaucoma in one report.This case addresses a gap in recognizing phentermine's independent effects when used separately.Case description: A 31-year-old woman with a medical history of diabetes, hypertension, and migraines was prescribed topiramate 25 mg nightly and phentermine 15 mg daily for weight loss management.She discontinued topiramate after 2 days due to nausea, but continued phentermine.More than 1 week after topiramate cessation, she developed acute bilateral blurred vision, eye pain, and tearing.Examination revealed intraocular pressures (IOP) of 55 and 53 mm Hg in the right and left eyes, respectively.Gonioscopy demonstrated complete 360 angle closure bilaterally.B-scan ultrasonography confirmed bilateral choroidal effusions, suggesting a nonpupillary block mechanism similar to topiramate-induced angle closure.Management included immediate phentermine discontinuation and intensive medical therapy with cycloplegic agents and steroid drops, and maximum medical treatment including intravenous mannitol, systemic and topical carbonic anhydrase inhibitors, topical -blockers, and agonists.IOPs normalized within 48 hours, and gonioscopy demonstrated open angles bilaterally by day 2. Conclusions: This case demonstrates that phentermine monotherapy can be associated with bilateral acute angle closure glaucoma through mechanisms similar to topiramate-induced closure, occurring even after topiramate discontinuation.The temporal relationship and presence of choroidal effusions strongly implicate phentermine as the primary causative agent.Clinical importance: Comprehensive ocular risk assessment is essential for all weight loss medications, including phentermine when used alone, to identify drug-induced angle closure mechanisms and guide prompt management to prevent serious complications.
Parekh et al. (Fri,) studied this question.