Acetazolamide and topiramate-induced clinically significant metabolic acidosis and weight loss in idiopathic intracranial hypertension: a case report and pharmacovigilance analysis.

Idiopathic intracranial hypertension (IIH) management often involves acetazolamide and topiramate, both carbonic anhydrase inhibitors. Their concurrent use poses a high, yet clinically under-recognized, risk of additive metabolic acidosis. We report a 44-year-old female with IIH who developed insidious, clinically significant hyperchloremic metabolic acidosis and profound weight loss (24% reduction) following prolonged combination therapy. Her clinical presentation mimicked malignancy, prompting extensive diagnostic screening before the pharmacodynamic interaction was identified. Acetazolamide discontinuation led to biochemical resolution. To systematically evaluate this interaction, we conducted a disproportionality analysis using the FDA Adverse Event Monitoring System (AEMS). The analysis corroborated strong safety signals for metabolic acidosis in combination therapy (ROR: 45.56, 95% CI: 28.66-72.43). This study highlights a distinct, chronic trajectory of acetazolamide-topiramate-induced acidosis. Clinicians must exercise heightened vigilance and enforce routine biochemical monitoring when co-prescribing these agents to prevent desirable therapeutic weight loss from transitioning into a debilitating adverse event.