For a study, researchers sought to examine the metabolic issues that topiramate users were experiencing and to find out whether or not these issues may be reversed after stopping the drug.
From January 2010 to July 2020, all progress notes produced by 5 endourologists from a single academic center that contained the phrases “topiramate” or “topamax” were retrospectively examined. Age more than 18 and the presence of either a 24-hour urine sample or stone analysis while taking topiramate were inclusion criteria. In addition, a subgroup of 18 individuals who provided 24-hour urine samples before and after stopping topiramate was also examined.
For the final analysis, 93 patients in all were included. About 24 hour urine samples were obtained for 67 patients, and they revealed mean calcium phosphate supersaturation of 1.9±1.1, mean pH of 6.6±0.5, and mean citrate excretion of 331±322 mg/d. In the subgroup analysis, quitting topiramate resulted in a reduction in pH from 6.59±0.54 to 6.33±0.47 (P=.06) and an increase in urine citrate excretion from 225 mg/d to 614 mg/d (P<.01). In addition, 114 stone occurrences occurred in 73 different patients, with 50% of the stones being composed mostly (≥50%) of calcium phosphate or being pure calcium phosphate.
Topiramate usage was accompanied by hypocitraturia and an increased pH, which was associated with a greater incidence of calcium phosphate stones than in the general population. After stopping topiramate, the pH returned to normal, and citrate excretion increased drastically. With drug withdrawal, these metabolic changes seem to be reversible.