Most people who take Topamax (topiramate) have little or no problem with side effects. Those with problems most often complain of:

• fatigue or drowsiness
• difficulty with concentration
• difficulty finding the right word (word retrieval)
• confusion
• dizziness
• ataxia
• paresthesias
• anorexia and weight loss

Most of these problems are mild to moderate. Many of them are more common when higher doses of Topamax are taken.

In December 2003, the labeling of Topamax was changed to include a warning about metabolic acidosis, which usually occurs early in treatment but can occur at any time. In controlled clinical trials, some degree of this electrolyte imbalance was found in 67% of pediatric patients and 32% of adults. Values were markedly abnormal in 11% of children and 3% of adults. See further discussion in the page on serious side effects.

The side effect of anorexia and weight loss is now a focus of research on Topamax. Data show that at least 5-10% of patients will lose weight, and therefore it is sometimes used in combination with Depakote (valproate), Neurontin (gabapentin), or Tegretol (carbamazepine), which can cause weight gain in some patients. Weight loss can be a problem, however, especially in children and those who are already thin.

Some other, less-common side effects were

• nervousness
• depression
• difficulty with memory

Idiosyncratic reactions
Idiosyncratic side effects include:

• allergic dermatitis
• oligohidrosis in children
• acute myopia
• secondary angle closure glaucoma