OriginalDrugs

Topiramate (Topamax)

  • Generic name: Topiramate
  • Brand names: Topamax, Topiragen, Topomac (UK), Topimax (DK, NO, SE)
  • Drug class: Anticonvulsant, Anti-epileptic

What is Topamax used for?

  • Epilepsy (prevent seizures) in adults and children who are at least 2 years old.
  • Migraine headaches prevention and reduction of the number of migraine attacks.
  • Prevention of episodic and chronic cluster headaches. However, topiramate will not treat a headache that has already begun.

Drug interactions

Topiramate is not a potent inducer of drug metabolising enzymes.

  • Carbonic anhydrase inhibitors (e.g., acetazolamide, dichlorphenamide): increased risk of kidney stone formation and hyperthermia. Avoid concomitant use.
  • Valproic acid: possible hyperammonemia with or without encephalopathy. Additionally, hypothermia has been reported with concomitant use of topiramate and valproic acid.
  • Oral contraceptives: decrease in ethinyl estradiol concentrations. Although topiramate's modest interaction with oral contraceptivess is not likely to interfere with contraceptive efficacy, the decrease in serum estrogen concentrations can increase the incidence of breakthrough bleeding. Therefore oral contraceptives should contain at least 35 mcg of estrogen.
  • Sumatriptan (Imitrex): no reported drug interactions with topiramate.
  • SSRI antidepressants (escitalopram, citalopram, sertraline, fluoxetine, paroxetine): no reported drug interactions with topiramate.

Topiramate and kidney stones

Topiramate (Topamax) increases the risk of calcium phosphate kidney stones formation tenfold. In the early research the kidney stone incidence was estimated at 1.5%.

Researchers found that long-term use of topiramate (more than 1 year) increased the urine pH and lowered urine citrate, an important inhibitor of kidney stone formation1. Also, topiramate is known to cause systemic metabolic acidosis - a buildup of excessive acid in the blood - as a result of the inability of the kidney to excrete acid.

Calcium phosphate stones tend to form when the urine is alkaline, meaning it has a high pH. To prevent the formation of calcium phosphate stones you can acidify urine by drinking cranberry juice or using vitamin C. Drinking enough water helps keep urine diluted and is the most important thing a person can do to prevent kidney stones.

Topiramate and osteoporosis

Osteoporosis may result from chronic, untreated metabolic acidosis, caused by long-term use of topiramate2.

However, there is no data in the literature showing that topiramate increases risk of osteoporosis to a great extent.

Can Topiramate worsen headaches?

In some people topiramate makes headaches worse3. About 10% of migraineurs develop a worsening of their symptoms while on this medication4.

Topiramate and Amitriptyline

Topiramate can be used together with amitriptyline to prevention migraine headaches5. The combination is useful in migraineurs who do not significantly benefit from using these medications alone.

Topiramate (Topamax) has no or little interaction with amitriptyline6.

References

  • 1. Welch BJ, Graybeal D, Moe OW, Maalouf NM, Sakhaee K. Biochemical and stone-risk profiles with topiramate treatment. Am J Kidney Dis. 2006 Oct;48(4):555-63. PubMed
  • 2. Mirza N, Marson AG, Pirmohamed M. Effect of topiramate on acid-base balance. Br J Clin Pharmacol. 2009 Nov;68(5):655-61.
  • 3. Martínez HR, Londoño O, Cantú-Martínez L, del Carmen Tarín L, Castillo CD. Topiramate as an adjunctive treatment in migraine prophylaxis. Headache. 2003 Nov-Dec;43(10):1080-4.
  • 4. Striano P, Zara F, Santorelli FM, Striano S. Topiramate-associated worsening symptoms in a patient with familial hemiplegic migraine. J Neurol Sci. 2008 Sep 15;272(1-2):194-5.
  • 5. Keskinbora K, Aydinli I. A double-blind randomized controlled trial of topiramate and amitriptyline either alone or in combination for the prevention of migraine. Clin Neurol Neurosurg. 2008 Dec;110(10):979-84.
  • 6. Bialer M, Doose DR, Murthy B, Curtin C, Wang SS, Twyman RE, Schwabe S. Pharmacokinetic interactions of topiramate. Clin Pharmacokinet. 2004;43(12):763-80.

Last updated: February, 2015

Good to know

topamax
  • Topamax was originally developed as a hypoglycemic agent that became an anticonvulsant afterward.
  • Topamax is a sulfamate-substituted monosaccharide, related to fructose, a rather unusual chemical structure for an anticonvulsant.
  • Many people experience weight loss while taking topiramate.