Topiramate: Pharmacokinetics and pharmacodynamics

Topiramate is a structurally novel anti-epileptic drug with at least 3 postulated mechanisms of action including: 1) potentiation of GABA responses, 2) impairment of AMPA/kainate glutamate receptors and 3) suppression of high frequency action potential firing. It has a favourable pharmacokinetic profile with rapid absorption, good bio-availability, linear pharmacokinetics, relatively long half-life and limited pharmacokinetic drug interactions. However, topiramate. can reduce the estrogen component of oral contraceptive medications. Women may require birth control preparations containing 50 mu g of estrogen. Topiramate clearance is reduced in severe renal failure and increased by enzyme-inducing antiepileptic drugs. The dose of topiramate may have to be reduced in renal failure or when withdrawing enzyme inducers.