Topiramate

Topiramate is an antiseizure medication. Its approved uses, per the Topamax label, are epilepsy — as initial single-drug therapy and as add-on therapy for several seizure types in patients aged 2 and older — and preventive treatment of migraine in patients aged 12 and older. Weight loss is not one of its approved indications.

It appears in obesity medicine because weight loss showed up as a side effect. In the epilepsy and migraine trials, anorexia and weight loss were among the most common adverse reactions, appearing at meaningfully higher rates than placebo. What is a nuisance in a seizure patient is a benefit in someone trying to lose weight, and that observation led to the combination product Qsymia, where extended-release topiramate is paired with phentermine.

The side effects are real and often the reason people stop. Paresthesias — tingling in the hands and feet — are common. So is altered taste, particularly a metallic flavor that makes carbonated drinks unpleasant. Word-finding difficulty and mental slowing are frequent enough to have earned the drug an informal nickname among patients. The Topamax label also warns about acute myopia and secondary angle-closure glaucoma.

The most important warning is about pregnancy. Pregnancy registry data show that infants exposed to topiramate in the womb have an increased risk of major congenital malformations including cleft lip and cleft palate, and of being small for gestational age. That is why Qsymia is distributed only through a restricted REMS program with monthly pregnancy testing. Topiramate prescribed for migraine carries the same fetal risk without the same distribution controls — something worth knowing if you take it for headaches.

Worth asking your clinician: whether pregnancy is possible for you, whether the cognitive side effects are tolerable at your dose, and how to taper rather than stop abruptly, since abrupt withdrawal of an antiepileptic can provoke a seizure. Our topiramate weight-loss review and Qsymia side-effect page go further.