Topiramate (Topamax)

When is topiramate used?

Topiramate is used to treat all seizure types either alone or in combination with other seizure medicines.

Topiramate is approved by the Food and Drug Administration (FDA) for use in patients 2 years of age and older with:

  • partial-onset seizures in people
  • generalized tonic-clonic seizures
  • seizures associated with Lennox-Gastaut syndrome

Topiramate is also used in other childhood epilepsies, in infantile spasms and myoclonic seizures.

Besides its use in epilepsy, when else is topiramate used?

Topiramate is FDA approved for use in patients with headaches.

Often doctors find that medicines are useful for more than one purpose. It is legal to prescribe medicines for "off-label uses" even though the FDA has not formally approved such use. Common off-label uses of topiramate include:

  • weight loss
  • pain syndromes
  • alcohol cravings in patients with alcohol abuse/dependence

What are the most common side effects of topiramate?

Most people who take topiramate have few or no side effects. Those with side effects might complain of:

  • fatigue or drowsiness
  • difficulty with concentration
  • difficulty finding the right word (word retrieval)
  • confusion
  • dizziness
  • unsteadiness
  • a feeling of pins and needles, usually in the tips of the fingers and toes
  • loss of appetite and weight loss
  • nervousness
  • depression
  • difficulty with memory

These problems are more common when higher doses of topiramate are taken.

If these problems do not go away within several days, or are really bothersome, call the doctor, but never stop or reduce the medicine on your own. Sometimes the doctor can help with these side effects by changing the prescription:

  • reducing the overall amount of topiramate
  • changing the amount taken at certain times, such as taking a greater proportion of the drug at bedtime to reduce daytime sleepiness
  • prescribing smaller doses at more frequent intervals

What are the most serious side effects of topiramate?

Very few people have serious reactions to topiramate. If you take it, you should be aware of them, however, so you and your family can recognize any early signs.

Glaucoma

A very small number of people treated with topiramate can develop an eye condition similar to glaucoma. If you experience blurred vision or difficulty seeing that comes on quickly, perhaps with eye pain, notify your doctor immediately. In those who have had such symptoms, they usually occurred during the first month of treatment. If action is taken promptly (including stopping the medication), the symptoms generally resolve but if no action is taken, permanent loss of vision could result.

Kidney stones

About 1 in 50 adults taking topiramate have developed kidney stones. Kidney stones are more common in men and in those who have had them before. They also may be more likely to occur if Diamox (acetazolamide) or Zonegran (zonisamide) is taken in combination with topiramate or if the patient is following the ketogenic diet (a special diet sometimes used to control seizures in children). Topiramate therefore should be used cautiously in people taking Diamox or Zonegran or following the ketogenic diet.

To help prevent kidney stones, patients should drink plenty of water, juice, or other fluids (8 glasses every day for adults). Sharp pains in the side or lower back may signal the onset of a kidney stone and the patient should seek prompt medical attention.

Acidosis

One factor that may increase the risk of kidney stones, fatigue, and other disorders is abnormally acid blood, called acidosis. This effect has been found to some extent in up to two-thirds of children taking topiramate and about one-third of adults. This is rarely serious.

The doctor will probably test the blood before starting treatment with topiramate and intermittently while topiramate is being used to check for acidosis. If the results are abnormal, the doctor may recommend stopping topiramate or starting treatment for acidosis to prevent any serious effects.

Inadequate sweating

Some children who take topiramate may not sweat enough in hot weather, causing their body temperatures to rise, sometimes to dangerous levels. Children should be monitored in hot weather to be sure they sweat appropriately.

A complete list of all reactions to topiramate can be found in the package insert. It is important to remember that most people tolerate topiramate well, and only a tiny number of people who take topiramate have a serious problem.

Who should not take topiramate?

The only people who definitely should not take topiramate are those who are allergic to it. People with a history of kidney stones should probably avoid topiramate. Also, people who need to take high doses of vitamin C or calcium supplements and those with existing kidney disease should be cautious with topiramate.

Can topiramate be taken with other medicines?

Sometimes one kind of medicine changes the way another kind of medicine works in the body. If two kinds of medicine affect each other, the doctor may prescribe something else or change the amount to be taken.

Topiramate can decrease the effectiveness of hormonal contraception including the birth control pill, hormonal injections or implants. Therefore women using these methods of birth control should be especially cautious as unplanned pregnancies are more likely to occur. To prevent pregnancy, a woman taking topiramate may need to use a different type of birth control, raise the dosage of the contraceptive or increase the frequency of the implant or injection. She should tell both the doctor prescribing contraception and the doctor prescribing topiramate about the other medicine so that the appropriate doses can be chosen. Topiramate does not affect barrier types of birth control, like condoms, non-hormonal IUDs, and diaphragms.

Topiramate also affects the way the body handles phenytoin (Dilantin, Phenytek), so if you take phenytoin, ask your doctor whether the dose of phenytoin should be adjusted.

How do other medicines affect topiramate?

Your body gets rid of topiramate more quickly if you are also taking certain seizure medicines, such as:

  • carbamazepine (Tegretol, Tegretol XR, Carbatrol)
  • phenytoin (Dilantin, Phenytek)
  • phenobarbital
  • primidone (Mysoline)

If this applies to you, your doctor may plan to give you more topiramate than you would otherwise take.

Any time one of your doctors suggests starting or stopping a prescription, be sure to ask how it may interact with topiramate and whether either dosage should be adjusted.

If a woman takes topiramate during pregnancy,
will it hurt the baby?

In the United States, the Food and Drug Administration (FDA) assigns each medication to a Pregnancy Category according to whether it has been proven to be harmful in pregnancy. Topiramate is listed in Pregnancy Category C. This indicates that caution is advised, but the benefits of the medicine may outweigh the potential risks. Studies in animals have shown some harm to the baby, but there have been no good studies in women. Talk to your doctor or another health professional if you are pregnant or plan to become pregnant. There is not yet enough information available to estimate the risk of birth defects if topiramate is taken during pregnancy. Nor is enough known to compare the risk with to the risk with other seizure medicines.

All women who are capable of becoming pregnant should take at least 0.4 mg (400 mcg) of the vitamin called folic acid every day because it helps to prevent specific birth defects called Neural Tube Defects. (The most well-known of these is spina bifida, in which the spinal cord is not completely enclosed.) Women with epilepsy should take between 1 and 4 mg of folic acid daily during their reproductive years. If the doctor thinks a woman is at especially high risk, the larger dose of folic acid—4 mg (4000 mcg) per day—may be recommended, beginning before the woman becomes pregnant.

Some babies born to mothers taking antiepileptic medications have had inadequate blood clotting within the first 24 hours after birth. It is often recommended that the mother be given 10 to 20 mg of vitamin K per day during the last month of pregnancy to prevent this problem.

Over 70% of topiramate from the mother’s blood passes through breast milk, but how much of this actually enters the baby’s bloodstream is not known. Further, how topiramate affects the baby is unknown. That said, it is strongly felt by neurologists and epileptologists that the benefits of breastfeeding largely outweigh the risks of exposing the baby to antiepileptic medications, including topiramate. As a matter of fact, the American Academy of Neurology and the American Epilepsy Society both recommend breastfeeding in women with epilepsy.