American Board of Internal Medicine (ABIM) Certification Practice Exam

What is a common side effect of topiramate?

1. Weight gain

2. Subclinical acidosis

3. Increased serum sodium levels

4. Epileptic seizures

The correct answer is: Subclinical acidosis

Topiramate is an anticonvulsant medication that is commonly used to treat epilepsy and to prevent migraines. One of the well-documented side effects of topiramate is its potential to cause metabolic acidosis, which can lead to subclinical acidosis. This effect is due to the drug’s inhibition of carbonic anhydrase, an enzyme that plays a key role in maintaining acid-base balance in the body. As a result of this inhibition, patients taking topiramate may experience a decrease in serum bicarbonate levels, contributing to a mild metabolic acidosis. In contrast, weight gain is not typically associated with topiramate; in fact, many patients on this medication may experience weight loss, making that option incorrect. While topiramate does interact with electrolyte balance, it does not lead to increased serum sodium levels; it may instead cause hyponatremia in certain cases. Lastly, while topiramate is used to control seizures, it is not responsible for increasing the incidence of seizures, thereby making it inadvisable to consider that as a side effect. Therefore, subclinical acidosis stands out as a notable side effect specifically linked to topiramate use.