Long-Term Side Effects of Topiramate for Migraines

Topiramate (Topamax) is a medicine used to treat epilepsy and prevent migraines. It decreases overly active brain signaling and is used alone or combined with other antiepileptic medicines to treat seizures. Topiramate is also used to prevent migraine headaches. In addition to short-term side effects, topiramate may cause certain long-term side effects.

Metabolic Acidosis

Topiramate may cause metabolic acidosis, which is an acid-base imbalance in the body that increases the acidity of the blood. Your doctor may test your blood's bicarbonate level before and during treatment with topiramate to check for this side effect. Your risk of metabolic acidosis increases if you take additional medicines that are structured like topiramate, such as acetazolamide (Diamox). Following a high-fat and low-carbohydrate diet may also increase your risk for topiramate-related acidosis.

If you develop metabolic acidosis, you may also experience kidney stones. Drinking 6 to 8 glasses of water each day helps prevent kidney stones. Metabolic acidosis may also cause loss of bone minerals, increasing your risk for fractures.

Suicidal Thinking

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Topiramate, as well as other antiepileptic medicines, may affect your mental health. You may have suicidal feelings, think about killing yourself or try to do so. This can happen within a week of starting topiramate or may take as long as 24 weeks after starting the medication. You and your family members should call your doctor right away if you notice panic attacks, agitation, restlessness, anxiety, depression, worsened irritability, difficulty sleeping, aggressiveness or thinking about harming yourself or ending your life.

The U.S. Food and Drug Administration Statistical Review and Evaluation: Antiepileptic Drugs and Suicidality -- an analysis of 11 antiepileptic medicines, including topiramate -- estimated that 1 of every 530 patients taking an antiseizure drug experiences suicidal thinking 3.

Birth Defects

Topiramate is not recommended if you plan to become pregnant because it may have a harmful effect on the fetus. It can increase the chance of the baby having birth defects, including cleft lip and cleft palate. Birth control is suggested if you plan to take topiramate and you should discuss this with your doctor.

Topiramate may cause certain birth control medicines not to work as well. If a woman becomes pregnant while taking topiramate, she should contact her doctor right away but not stop taking the medication suddenly. Seizures may occur if topiramate is suddenly stopped, even if you have not had seizures in the past.

Changes in Body Temperature

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Topiramate may cause changes in body temperature or changes in blood ammonia. According to the FDA-approved prescribing information, a side effect of topiramate is decreased sweating with increased body temperature, or hyperthermia 1. This rare side effect typically occurrs about 4 to 5 months after starting treatment.

Another side effect is decreased body temperature, or hypothermia, if topiramate is taken with valproic acid (Depakene), which is another medicine used for seizures. This can occur with normal or elevated levels of ammonia in the blood. Symptoms of an elevated ammonia level include tiredness and confusion. Report these symptoms to you doctor right away if they occur.