Topamax (Topiramate) Uses and Side Effects

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 and 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 for Taking Topamax

Topamax has both approved and off-label uses. In the United States, the drug is officially approved by the Food and Drug Administration (FDA) for:

• Migraine prevention in adults and adolescents 12 and older
• Partial-onset seizure treatment in adults and children two and older
• Primary generalized tonic-clonic seizure treatment in adults and children two 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)
• Depression
• Post-traumatic stress disorder (PTSD)
• Tourette syndrome
• Weight loss (specifically to control binge-eating and purging)

Topamax 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 and 25mg. The dosage can vary by the condition being treated and the person's age.

When starting treatment, the dosage is typically tapered up to reduce the risk of side effects. It takes approximately five days for the medication to build up and reach a steady state in a person's system.

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 of Topamax

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:

• Bruising or bleeding
• Changes in menstruation
• Cognitive difficulties
• Constipation
• Diarrhea
• Dizziness
• Double vision
• Dry mouth
• Headache
• Heartburn
• Loss of appetite
• Mood changes
• Muscle or bone pain
• Nausea
• Nervousness
• Paresthesia
• Sleepiness
• Slow reactions
• Stomach upset
• Taste changes
• Tingling or prickly skin sensations
• Tremors
• Weakness
• Weight loss

Paresthesia is an abnormal sensation, often a tingling or prickling of the skin, that most commonly affects the arms and legs. While usually painless, it is one of the most common reasons why people discontinue the drug.

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:

• Glaucoma: In some individuals, Topamax can 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: 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.
• Metabolic acidosis: This is the potentially serious build-up of acid in the blood, most often seen in children 15 and under that can be caused by Topamax usage. Symptoms include nausea, vomiting, fast breathing, and lethargy. If left untreated, metabolic acidosis can lead to coma and death.
• Pregnancy: If taken during pregnancy, Topamax may cause issues for the fetus, including a cleft palate and small size for their gestational age. This medication can also be found in breastmilk. While Topamax is not absolutely contraindicated, you must weigh the benefits and consequences of treatment if you are pregnant, planning to get pregnant, or breastfeeding.

Topamax Drug Interactions

Certain drugs are known to interact with Topamax, either by reducing or increasing the availability of Topamax 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 carbonic anhydrase 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.