Topamax (topiramate) is an anticonvulsant medication used in the treatment of epilepsy and migraine headaches. Topamax is also commonly used off-label to treat a wide range of mood disorders, eating disorders, and to aid in substance abuse therapy. While Topamax’s mechanism of action is unclear, we know that the drug blocks sodium channels in the body that deliver electrical impulses to excitable cells (such as nerve, muscle, and brain cells). By doing so, Topamax appears to enhance the activity of a chemical messenger (neurotransmitter) known as gamma-aminobutyric acid (GABA).
Indications
Topamax has both its approved and off-label uses. In the United States, the drug is officially approved by the U.S. Food and Drug Administration (FDA) to:
- Treat partial-onset seizures in adults and children two and older
- Treat primary generalized tonic-clonic seizures in adults and children two and older
- Prevent migraines in adults and adolescents 12 and older
Topamax can also be in combination with other drugs to treat partial-onset seizures, primary generalized tonic-clonic seizures, and seizures associated with Lennox-Gastaut syndrome (a severe form of childhood epilepsy). Among its off-label uses, Topamax is sometimes prescribed to treat:
- Alcohol dependency
- Bipolar disorder
- Borderline personality disorder (BPD)
- Cocaine and methamphetamine addiction
- Obsessive-compulsive disorder (OCD)
- Post-traumatic stress disorder (PTSD)
- Weight loss (specifically to control binge-eating and purging)
Dosing
Topamax is available in capsule and tablet formulations. The tablet is offered in a 25-, 50-, 100-, and 200-milligram (mg) dose. The capsule is available in 15-mg or 25-mg dose. The dosage can vary by the condition and the age of the user. When starting treatment, the dosage is typically tapered up to reduce the risk of potential side effects. It should also be tapered down if the decision is made to stop treatment. Stopping abruptly can cause a rebound of disease symptoms (such as seizures in people with epilepsy or abnormal moods in people with bipolar disorder). When prescribed for smaller children, the Topamax capsule can be broken open and its contents sprinkled over food.
Common Side Effects
Topamax has a number of side effects that tend to be transient and resolve on their own as the body adapts to the treatment. Most are mild to moderate in severity. Common side effects include:
- Severe eye pain with vision blur or loss
- Diarrhea
- Dizziness
- Double vision
- Loss of appetite
- Mood changes
- Nausea
- Stomach upset
- Taste changes
- Tingling or prickly skin sensations
- Tremors
- Weakness
- Weight loss
Any persistent, severe, or worsening side effects should be reported to your doctor immediately.
Considerations and Complications
Less commonly, Topamax may cause serious complications that require you to either stop or avoid treatment. Among them:
- Topamax should be used with caution in pregnancy. Topamax is classified as a category D drug due to evidence that it may cause a cleft palate in some children. While Topamax is not absolutely contraindicated in pregnancy or breastfeeding, you must weigh the benefits and consequences of treatment if you are pregnant or planning to get pregnant.
- Topamax may cause metabolic acidosis. This is the potentially serious build-up of acid in the blood, most often seen in children 15 and under. Symptoms include nausea, vomiting, fast breathing, and lethargy. If left untreated, metabolic acidosis can lead to coma and death.
- Topamax can sometimes cause glaucoma. Symptoms usually appear within a month of starting treatment and may be recognized by the sudden blurring of vision, eye pain, redness, and abnormally dilated pupils.
- Kidney damage can also occur. This most often affects people over 65 who have an underlying kidney disorder. Kidney function tests should be routinely performed to monitor for any abnormalities. Kidney stones have also been known to develop in Topamax users, the risk of which may be reduced by drinking plenty of water.
Drug Interactions
Certain drugs are known to interact with Topamax, either by reducing or increasing the availability of Topomax or the other co-administered drug. This is especially true when used with other anticonvulsants such as Tegretol (carbamazepine) and Lamictal (lamotrigine). Dose adjustments may be required to compensate for this effect. Other co-administered drugs that may require dose adjustments include the diuretic Microzide (hydrochlorothiazide) and the diabetes medications Actos (pioglitazone) and metformin. Among the drugs to be avoided are those classified as carboanhydrase inhibitors, which include:
- Diuretics such as Keveyis (dichlorphenamide)
- Epilepsy drugs such as Diamox (acetazolamide) and Zonegran (zonisamide)
- Glaucoma medications such as Azopt (brinzolamide), Neptazane (methazolamide), and Trusopt (dorzolamide)
- Estrogen-based contraceptives may also be compromised if taking Topamax, increasing the risk of pregnancy and breakthrough bleeding.