If you have migraine headaches, you may receive a prescription for Topamax, or topiramate. This anti-seizure drug has been found to be effective in decreasing migraine headaches when given each day. Unfortunately, taking Topamax increases your risk of developing another medical problem – kidney stones.
Topamax is a drug called a neuromodulatory agent, meaning it can influence the overall activity level of the brain. It is this effect that helps to prevent seizures and migraines, both of which are disorders that result from imbalances in electrical activity or brain chemistry. In addition to the beneficial effects on the brain, however, Topamax also affects the kidneys. Topamax inhibits the activity of certain enzymes in the kidney, leading to high levels of calcium in the urine and an elevated urine pH, which means the urine is more alkaline. The combination of calcium and alkalinity sets the stage for kidney stones.
The most common type of kidney stone is the calcium oxalate stone, a combination of the mineral calcium and the mineral salt of oxalic acid. This solid aggregation of minerals can cause severe pain, nausea, vomiting and blood in the urine. A large stone can block the ureter – the tube leading from the kidney to the bladder – and cause infection or renal failure if not treated. In some cases, surgery or other medical treatments are necessary to remove the stone. Men are more susceptible to kidney stones than women; most men who develop kidney stones experience their first attack between age 30 and 40. Repeated attacks are more likely once the first stone occurs.
Many physicians are unaware of the connection between Topamax and kidney stones, as the research on this issue is fairly new. A study published in the October 2011 issue of “Epilepsia” found that 5% of children on Topamax for seizures developed kidney stones within one year of the initial prescription. Another study reported in the February 2011 issue of “Urology” noted that even after long periods of taking Topamax, all patients on the drug had decreased levels of urinary citrate, another risk factor for kidney stone development.
How great is the risk? The incidence of kidney stones in the general population is about 0.2%. For those taking Topamax, the risk of kidney stones climbs to 1.5%, over five times higher. You can help decrease your chances of developing a kidney stone while on Topamax by drinking more water – 32 to 64 ounces a day is the amount recommended – in addition to other sources of fluids such as coffee or tea. Extra vitamin C can help make your urine more acid, which counteracts the alkalizing effect of Topamax. If you are considering Topamax, be sure to check for a history of kidney stones in your family and tell the clinician who is treating you. If you’ve already had a kidney stone, it’s even more important to have that information in your medical records.
Sources
Epilepsia: Incidence of Kidney Stones with Topiramate Treatment in Pediatric Patients http://www.ncbi.nlm.nih.gov/pubmed/21883178
Urology: Patients with and without Prior Urolithiasis have Hypocitraturia and Incident Kidney Stones While on Topiramate http://www.ncbi.nlm.nih.gov/pubmed/20888032
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