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Wednesday, August 20, 2014

Contraception is any method by which pregnancy is avoided. Among the popular ones are barrier methods, hormonal contraceptives (“the pill”), intra uterine devices, and sterilization. While the choice of contraception depends on preferences, oral contraceptives are the most common ones and are affected by anti-epileptic drugs (AEDs).

Contraceptives contain estrogen and progesterone in various combinations and can be used in various forms like pills, transdermal patches, subdermal implants, injections, vaginal rings, etc. Since AEDs carry an increased risk of birth defects in children exposed to these drugs during pregnancy, effective contraception is important in epilepsy.

Some AEDs are enzyme inducers, meaning they enhance the breakdown of certain drugs by the liver. These AEDs increase the metabolism of oral hormonal contraceptives, which can lead to the failure of this contraception method. This can in turn expose the fetus to birth defects.

When using hormonal contraceptives and enzyme inducing AEDs together, it is worth a discussion with your doctor about birth control effectiveness. For women taking enzyme inducing AEDs, increasing the dose of hormonal contraceptives or switching to non-enzyme inducing AEDs are considered. In this context it is worth mentioning that a number of factors have to be considered in prescribing AEDs; hence changing medications or dosages should only be tried by a qualified practitioner.

Provided below is the list of enzyme inducing and non-enzyme inducing AEDs.

Enzyme inducing AEDs (May increase the chance of failure of hormonal contraceptives) Non-enzyme inducing AEDs (not known to reduce efficacy of hormonal contraceptives)
Topiramate (Topamax) Tiagabine (Gabitril)
Carbamazepine (Tegretol) [strong inducer] Levetiracetam (Keppra)
Phenobarbital Lamotrigine (Lamictal)
Felbamate (Felbatol) Valproate (Depakote)
Phenytoin (Dilantin) [strong inducer] Zonisamide (Zonegran)
Oxcarbazepine (Trileptal) Gabapentin (Neurontin)
Primidone (Mysoline) [strong inducer]  
Phenobarbital [strong inducer]  

 

Authored by: Selim R. Benbadis, MD | Raghav Sista on 8/2014
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