topiramate, Topamax

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Pharmacy Author:

Omudhome Ogbru, PharmD

Omudhome Ogbru, PharmD

Dr. Ogbru received his Doctorate in Pharmacy from the University of the Pacific School of Pharmacy in 1995. He completed a Pharmacy Practice Residency at the University of Arizona/University Medical Center in 1996. He was a Professor of Pharmacy Practice and a Regional Clerkship Coordinator for the University of the Pacific School of Pharmacy from 1996-99.

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Medical and Pharmacy Editor:

Jay W. Marks, MD

Jay W. Marks, MD

Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles.

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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, with the abnormal activity spreading to other portions of the brain. Although topiramate's exact mechanism of action is unknown, 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: Yes

PREPARATIONS: Tablets: 25, 50, 100, and 200 mg. Sprinkle Capsules: 15 and 25 mg.

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

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 alone or in combination with other anti-seizure drugs to treat individuals two years old or older 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 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% 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 by 25 to 50 mg per week until an effective daily dose is reached.

For children 10 years or older and adults the dose may be increased by 100 mg in week 5 and 6 when topiramate is used alone. This slow approach to treatment reduces side effects.

The recommended final adult dose is 200-400 mg divided and given as two doses daily.

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 administered in two divided doses. The target dose is 5 to 9 mg/kg per day as a divided dose.

Migraine is treated 25 mg nightly for the first week then increased by 25 mg weekly up to a maximum dose of 100 mg administered as a divided dose.

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 and metabolic acidosis: acetazolamide (Diamox), dorzolamide (Trusopt), methazolamide (Neptazane), dichlorphenamide (Daranide).

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

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