GENERIC NAME: topiramate

BRAND NAME: Topamax

DRUG CLASS AND MECHANISM: Topiramate is an oral drug that is used to prevent the seizures of epilepsy. (It is an anti-epileptic or anti-seizure drug). It is used primarily among patients who are not controlled by other anti-epileptic drugs. About 1 in 4 Americans diagnosed with epilepsy has seizures that resist treatment with other anti-epileptic drugs.  Topiramate also prevents migraine headaches.

Seizures are due to the abnormal activity ("firing") of nerves in the brain, and the abnormal activity spreads to smaller or larger portions of the brain. Although topiramate's exact mechanism of action is unknown, scientific studies suggest that it may alter neurotransmitters within the brain. Neurotransmitters are chemicals that nerves manufacture and use to communicate with other nearby nerves. By altering the production or action of the neurotransmitters, topiramate may suppress the abnormal activity of the nerves in the brain that cause the seizures or may prevent the abnormal activity from spreading to other nerves. Other studies suggest that topiramate may suppress the nerves directly (i.e., not by altering neurotransmitters) and make them less likely to fire. The FDA approved topiramate as a tablet in 1997. The Sprinkle Capsules were approved in October, 1998.

PRESCRIPTION: Yes

GENERIC AVAILABLE: No

PREPARATIONS: Tablets: 25, 100 and 200 mg. Sprinkle Capsules: 15 and 25 mg.

STORAGE: Topiramate tablets should be stored at room temperature, 59-86°F (15-30 ° C). Sprinkle capsules should be stored at or below 77 ° F (25 °C).

PRESCRIBED FOR: Seizures may be classified as either partial if they involve only a small portion of the brain or generalized if they involve more of the brain. Topiramate is used in combination with other anti-seizure drugs among adults and children aged 2-16 years with partial seizures or generalized tonic-clonic seizures (in which there is prolonged contraction of the muscles of the body that causes rigidity as well as jerking motions). Topiramate sprinkle capsules are approved for treatment without other drugs in patients 10 years of age and older.  Topiramate also is used in patients two years of age and older with seizures associated with the Lennox-Gastaut Syndrome, a severe form of epilepsy which accounts for up to 10 percent of all cases of childhood epilepsy. Children with Lennox-Gastaut Syndrome experience delays in their development and up to dozens of different, mixed types of seizures a day. The most common types of seizures in this syndrome are tonic (stiffening of the body, with the eyes rolling upwards, dilation of the pupils and shallow, irregular breathing), atonic (brief loss of muscle tone and consciousness, causing abrupt falls), myoclonic (sudden muscle jerks), and absence (staring spells).

Topiramate also is approved for the prevention of migraine headaches in adults.

DOSING: Most commonly, topiramate is started in low doses, 25 or 50 mg per day, and then increased slowly, under a doctor's orders, by 25 to 50 mg per week until an effective daily dose is reached. This slow approach to treatment reduces side effects.

In children, the starting dose is up to 25 mg (1 to 3 mg/kg/day), taken nightly for the first week. The dose is then increased at 1 or 2 week intervals by 1 to 3 mg/kg/day.

Although the usual adult dose is 200 mg twice daily, some adult patients may begin to see a clinical response at 200 mg per day. Some patients need doses higher than 200 mg daily. In children, the usual dose is 2.5 to 4.5 mg/kg twice daily.

Patients should maintain an adequate fluid intake in order to minimize the risk of kidney stones.

DRUG INTERACTIONS: The following medications, when taken with topiramate, increase the risk of kidney stones: acetazolamide (Diamox), dorzolamide (Trusopt), methazolamide (Neptazane), dichlorphenamide (Daranide).

Carbamazepine (Tegretol) and phenytoin (Dilantin) markedly decrease the amount of topiramate in the body by increasing its elimination from the body. As a result, topiramate may lose effectiveness unless doses are increased.

Topiramate may decrease the amount of estrogen in the body in women taking oral contraceptives, possibly increasing the chances of unwanted pregnancy.

Patients with seizure disorders taking anticonvulsant medications, including topiramate, may develop nerve toxicity from a chemical, 4'-O-methylpyridoxine, found as a contaminant in some ginkgo preparations.

PREGNANCY: Topiramate has been associated with abnormalities of the fetus (teratogenicity) in experimental animal studies. No data on fetal effects of topiramate exists in humans.

NURSING MOTHERS: Topiramate is excreted in the milk of lactating rats. It is not known whether topiramate is excreted in human milk or if it has important effects on nursing infants.

SIDE EFFECTS: In adults, the most common side effects of topiramate are tiredness, dizziness, coordination problems, speech problems, changes in vision or double vision, difficulty with memory, and sensory distortion.

In children, the most common side effects are drowsiness, tiredness, loss of appetite, nervousness, difficulty with concentration/attention, weight decrease, aggressive reaction and difficulty with memory.

Since topiramate was approved, there have been 23 cases reported (as of 8-17-01) of a sudden onset of vision and eye problems. Symptoms have typically occurred within the first month of therapy, with patients reporting an acute onset of decreased vision and/or eye pain. Eye examination revealed myopia (nearsightedness), redness, decreased depth of the anterior chamber of the eye and elevated ocular pressure, with or without dilation of the pupils. Fluid accumulation within the eye may displace the lens and iris anteriorly causing secondary angle closure glaucoma. If patients develop this syndrome, the treatment is to discontinue topiramate as rapidly as possible, according to the judgment of the treating physician.

Pharmacy Author: Emmanuel Saltiel, Pharm.D.
Medical/Pharmacy Editor: Jay W. Marks, M.D.

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From the Doctors at MedicineNet.com

Migraine Headache - Learn about migraine headache including symptoms such as intense throbbing pain in the temple area of head. Migraine triggers vary from person to person. Source:MedicineNet Epilepsy Treatment - Information on Epilepsy treatment includes how epilepsy is treated, drug therapy, side effects, and surgery. Source:WebMD Medical Reference from The Cleveland Clinic Fragile X Syndrome - Read about Fragile X syndrome (FXS or Martin-Bell syndrome) causes, signs, symptoms, and treatments. Learn the facts about the most common inherited form of mental retardation. Source:Government Read 33 more topiramate related articles ... Epilepsy Drug Doesn't Prevent Migraines Suicide Risk From 11 Epilepsy Drugs Seizure Drug May Treat Alcoholism Migraine Drug Ups Kidney Stone Risk

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Last Editorial Review: 10/16/2005