What You Should Know About the Drug Topamax/Topiramate

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Topamax (generic topiramate) is an anticonvulsant medication approved by the US Food and Drug Administration (FDA) for use in treating epilepsy and migraine headaches. While Topamax has been and continues to be studied for use in the treatment of bipolar disorder, it is not FDA approved for such use. However, many doctors do prescribe Topamax off-label for bipolar disorder.

Two recent clinical studies' results agreed with those of older studies, finding that Topamax was effective for bipolar disorder when used as an add-on to other mood stabilizers but not particularly effective when used alone.

Topamax is often misspelled as Topomax.

Topamax comes in tablets and in capsules that may be opened and sprinkled onto soft food such as pudding, yogurt, ice cream, and other food that does not require chewing. If using Topamax sprinkle capsules, you should eat the entire serving of food immediately; do not store it for later.

Major Warnings on Topamax

  1. Metabolic Acidosis. Topamax use is associated with this condition, in which the blood becomes too acidic. There is a higher risk of developing metabolic acidosis in pediatric patients 15 and under. Symptoms are rapid breathing (hyperventilation), fatigue, refusal to eat, and stupor. This condition can be serious if not treated. The approved label for Topamax recommends measuring blood acidity when beginning treatment and periodic testing.
  1. Glaucoma. A syndrome consisting of acute nearsightedness (myopia) associated with an eye disorder called secondary angle closure glaucoma has occurred in patients using Topamax. Symptoms generally appear within a month of starting Topamax treatment and include sudden blurring of vision, eye pain, and sometimes redness or widely dilated pupils. If you experience any of these symptoms, contact your prescribing physician immediately. If the prescribing physician is not available, contact an ophthalmologist.
  1. Decreased Sweating and Fever. This has primarily been reported in children, and patients should be monitored for these symptoms, especially in hot weather. Because many other prescribed and over-the-counter medications can make a person extra sensitive to heat, make sure your doctor and pharmacist know all the drugs the patient is taking. 
  2. Do not stop taking Topamax abruptly. There is an increased risk of seizures if this is done.
  3. Kidney Stones. There is an increased risk of developing kidney stones when taking Topamax. Be sure to drink plenty of fluids.
  4. Renal Impairment. Since Topamax is cleared from the body through the kidneys, dosage may need to be adjusted in patients with renal impairment, particularly in those aged 65 and older.

Topamax Drug Interactions

  1. Other Anticonvulsants. In clinical trials, combining Tegretol (carbamazepine) with Topamax resulted in a 40% decrease in the level of Topamax available. With Lamictal (lamotrigine), the level of Topamax increased 15%, and with Depakote (valproic acid), both drugs' concentrations were lowered 11-14%. However, Topamax and Depakote combined create a risk for a condition called hyperammonemic encephalopathy. Symptoms are acute alteration in​ the level of consciousness and/or cognitive function with lethargy or vomiting.
  1. Oral Contraceptives. There is a risk of decreased contraceptive protection and breakthrough bleeding when taking Topamax with contraceptives containing estrogen.

There are a number of other possible drug interactions. Read the prescribing information carefully and again, make sure your doctor and pharmacist know all the other medications, both prescribed and over-the-counter, that you are taking.

Topamax and Pregnancy/Breast-Feeding

Animal studies showed a significant danger to the fetus from Topamax, and in humans, there is a significantly increased risk of birth defects known as oral clefts. It is imperative to consult your prescribing doctor if you are pregnant or planning to become pregnant.

Topamax should be used during pregnancy only if the potential benefit outweighs the potential risk to the unborn child. Although there are no controlled studies on the secretion of Topamax in milk, evidence suggests it is secreted extensively, and again, weigh the benefits and risks carefully.

Common Side Effects of Topamax and Topiramate

The most commonly reported side effect of Topamax is paresthesia or tingling of the extremities. The side effects that most caused people to drop out of clinical trials were sleepiness and fatigue. Reports of fatigue increased at higher dosages. Since there is a potential for dizziness, confusion, and difficulty concentrating, do not drive or operate machinery until you know how you react to this medication.

Other common side effects include:

  • Loss of appetite
  • Weight loss
  • Difficulties with memory, concentration or attention
  • In children, upper respiratory infection

Topamax and Weight Loss

Much has been made about the possibility of losing weight on Topamax. In clinical trials, weight decrease occurred in up to 21% of subjects, usually less than that, and was dose-dependent, with the greatest number of people losing weight on 400mg per day. Since the risk of side effects increases with a higher dose, each person must evaluate his or her own response to the drug.


Kushner, S.F., Khan, A., Lane, R., Olson, W.H. (2006). "Topiramate Monotherapy in the Management of Acute Mania: Results of Four Double-Blind Placebo-Controlled Trials." http://www.ncbi.nlm.nih.gov/entrez/...&list_uids=16411977.

McIntyre, R.S., Riccardelli, R., Binder, C., Kusumakar, V. (2005). "Open-Label Adjunctive Topiramate in the Treatment of Unstable Bipolar Disorder." http://www.ncbi.nlm.nih.gov/entrez/...&list_uids=16086539....

Medline Plus Medical Encyclopedia. (2005). "Glaucoma." https://medlineplus.gov/ency/article/001620.htm.

Medline Plus Medical Encyclopedia. (2006). "Metabolic Acidosis." https://medlineplus.gov/ency/article/000335.htm.

US Food and Drug Administration. (2005). "FDA Approved Labeling Text Dated 6/29/05 for Topamax® (topiramate) Tablets and Topamax® (Topiramate Capsules) Sprinkle Capsules."