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

Antiepileptic medications have been associated with increased risk of suicidal thinking and behavior. Anyone considering the use of antiepileptic drugs must balance this risk of suicide with the clinical need. Patients who are started on therapy should be closely observed for clinical worsening, suicidal thoughts, or unusual changes in behavior. USES: Topiramate is used to treat a seizure disorder (epilepsy). This medication is also used to prevent migraine headaches. HOW TO USE: This drug is taken by mouth, generally twice daily. Dosage is slowly increased over several weeks and adjusted to improve seizure control. Because of the bitter taste, do not chew or crush tablets. Doses above 400 mg daily generally are not more effective than lower doses. If it is necessary to discontinue this drug, generally the dosage should be decreased slowly, not stopped suddenly. Use exactly as directed. Do not stop using your other seizure medications unless directed to do so. SIDE EFFECTS: Weakness, tiredness, drowsiness, dizziness, tingling sensations, loss of appetite and weight loss may occur. If these persist or worsen, notify your doctor promptly. Report promptly: unsteadiness, slowing or shakiness, speech problems, mental/mood changes, stomach/abdominal pain. Unlikely but report promptly: itching, trouble or rapid breathing, fast/slow/irregular heartbeat, loss of consciousness, fever, persistent sore throat. Seek immediate medical attention if any of these rare but very serious eye problems occur: sudden vision change/blurred vision, eye pain or redness. Topiramate infrequently can cause decreased sweating, which could raise your body temperature (hyperthermia). The risk of this serious side effect is greater in hot weather and/or during vigorous exercise, especially in children. Drink plenty of fluids and dress lightly while in hot climates, or when exercising. Check carefully for signs of decreased sweating. If this occurs, promptly seek cooler or air-conditioned shelter and/or stop exercising. Seek immediate medical attention if your body temperature is above normal, or if you have mental/mood changes, headache or dizziness. Consult your doctor for more details. If you notice other effects not listed above, contact your doctor or pharmacist.