Adverse Effects
A GlaxoSmithKline-sponsored Phase IV study suggested that cognitive side effects may be more common with topiramate than with lamotrigine. In studies of healthy volunteers, therapeutic doses of topiramate for bipolar disorder produced greater cognitive deficits than lamotrigine, including short term memory loss and word-finding difficulty.
Side-effects reported by > 10% of subjects in at least one clinical study (listed by prevalence):
- paresthesia (numbness & tingling) (23.7%)
- upper respiratory tract infection (17.5%)
- diarrhea (16.8%)
- nausea (15.4%)
- anorexia (loss of appetite) (13.3%)
- memory problems (11.2%)
Side-effects most frequently leading to discontinuation of therapy with topiramate:
- psychomotor slowing (4.1%)
- memory problems (3.3%)
- fatigue (3.3%)
- confusion (3.2%)
- somnolence (3.2%)
That same study also reported that in adult patients with Bipolar 1 disorder who were already receiving either lithium or valproate, the addition of topiramate did not produce a statistically significant improvement versus placebo, while adding the above adverse reactions.
Rarely, the inhibition of carbonic anhydrase may be strong enough to cause metabolic acidosis of clinical importance.
The U.S. Food and Drug Administration (FDA) has notified prescribers that topiramate can cause acute myopia and secondary angle closure glaucoma in a small subset of people who take topiramate regularly. The symptoms, which typically begin in the first month of use, include blurred vision and eye pain. Discontinuation of topiramate may halt the progression of the ocular damage, and may reverse the visual impairment.
Preliminary data suggests that, as with several other anti-epileptic drugs, topiramate carries an increased risk of congenital malformations. This might be particularly important for women who take topiramate to prevent migraine attacks. In March 2011 the FDA notified healthcare professionals and patients of an increased risk of development of cleft lip and/or cleft palate (oral clefts) in infants born to women treated with Topamax (topiramate) during pregnancy and placed it in Pregnancy Category D.
Topiramate has been associated with a statistically significant increase in suicidality, and "suicidal thoughts or actions" is now listed as one of the possible side effects of the drug "in a very small number of people, about 1 in 500."
Read more about this topic: Topiramate
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