Topiramate (Topamax) is an anticonvulsant medication that is FDA-approved for headache and migraine prevention.
Researchers at the University of Texas Southwestern Medical Center at Dallas have completed a study showing that topiramate can increase the risk of developing kidney stones. Although there has been some discussion of this potential side effect, this is the first study to formally investigate the issue and examine the mechanism of stone formation.
"The wide-spread and escalating use of
topiramate emphasizes the importance of considering the long-term impact of this
drug on kidney stone formation," said Dr. Khashayar Sakhaee, senior author of
the study and chief of mineral metabolism at UT Southwestern.
Study methods
This was a two-phase study:
Phase 1: Thirty-two patients treated with topiramate and 50 healthy volunteers participated in a cross sectional study. Blood and urine test results were evaluated for kidney stone risk.
Phase 2: A short-term study was conducted in seven patients treated with topiramate to assess kidney stone risk before, and three months after, topiramate treatment.
Patients for both studies were referred from the Neurology Department at UT Southwestern Medical Center, and control subjects in the cross-sectional study were healthy volunteers. None of the patients had primary hyperparathyroidism (overactivity of the parathyroid glands), gastrointestinal disease, or kidney problems. Any of those conditions would have increased the patients' risk of developing kidney stones.
Study conclusions
Based on the results of blood and urine tests, treatment with topiramate increases the risk of forming kidney stones because the drug causes systemic metabolic acidosis and changes in urine chemistry.
To date, the reported incidence of kidney
stones while taking topiramate has been 1.5 percent. This rate might be underestimated because of the short time frame of studies, and the lack of ongoing studies for kidney stones and topiramate.
Summary
In addition to some anecdotal evidence we had prior to this study, we now have a clinical study demonstrating that long-term use of topiramate increases the risk of developing kidney stones. Dr. Sakhee commented, "There is a legitimate concern for the occurrence of kidney stones with long-term topiramate treatment... Studies are needed to explore optimal measures to prevent kidney-stone formation with topiramate use." If you are considering taking topiramate, please discuss this issue with your doctor, especially if you have a history of kidney stones or any problems with kidney function.
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Resources:
Welch, Brian J.. MD; Graybeal, Dion, MD; Moe, Orson W., MD; Maalouf, Naim M., MD; Sakhee, Khashayar, MD. "Biochemical and Stone-Risk ProfilesWith Topiramate Treatment." Am J Kidney Dis 48:555-563. doi:10.1053/j.ajkd.2006.07.003.
Newswise. "Drug Prescribed for Migraines and
Seizures Increases Risk of Kidney Stones." October 31, 2006.
