Association Between Topiramate Use and Serum Bicarbonate Levels in a Veteran Population

Background: Topiramate has been associated with metabolic acidosis secondary to decreased serum bicarbonate. Product labeling recommends serum bicarbonate monitoring at baseline and periodically thereafter. Objective: The study objective was to assess changes in serum bicarbonate within the first year of topiramate use in an outpatient veteran population. Methods: This was a single-center, retrospective study conducted at the Iowa City Veterans Affairs Health Care System. Inclusion criteria required a minimum of 1 topiramate outpatient prescription between October 1, 1999, and August 31, 2012, and at least 1 serum bicarbonate level within 12 months prior to topiramate initiation. Patients with topiramate nonadherence, concurrent use of sodium bicarbonate or oral carbonic anhydrase inhibitors, and individual serum bicarbonate values obtained during inpatient hospitalizations were excluded. Change in bicarbonate was evaluated using a paired t test. Decreases in bicarbonate of ≥5 mEq/L, values