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contraception and epilepsy

Some methods of contraception may be less effective in preventing pregnancy for women taking certain anti-epileptic drugs (AEDs). This is because some AEDs (enzyme-inducing AEDs) affect how well methods of contraception work.  Non-enzyme-inducing AEDs are unlikely to affect contraception.

Enzyme-inducing AEDs

Enzyme-inducing AEDs may make some methods of contraception less effective.

Drug (generic name)

Available as (brand name)

carbamazepine

Tegretol

eslicarbazepine acetate

Zebinix

oxcarbazepine 

Trileptal

phenobarbital

no brand name

phenytoin

Epanutin

primidone

Mysoline

rufinamide

Inovelon

topiramate

Topamax

perampanel

Fycompa

Enzyme-inducing AEDs may affect methods of contraception that contain hormones, such as the Pill or contraceptive implants. This is because they increase the level of enzymes that break down hormones in the body. This means the hormones in contraceptives are broken down more quickly than usual, so they stay in the body for less time and are less effective in preventing pregnancy.

If you take an enzyme-inducing AED, you may be advised by your doctors to use a method of contraception that is not affected by your AED, such as a barrier method, or to use more than one method to help prevent pregnancy.

Non-enzyme-inducing AEDs

Non-enzyme-inducing AEDs are unlikely to affect any form of contraception.

Drug (generic name)

Available as (brand name)

acetazolamide 

Diamox

Briviact 

Brivaracetam

clobazam

Frisium

clonazepam

Rivotril

ethosuximide

Zarontin, Emeside

gabapentin 

Neurontin

lacosamide

Vimpat

levetiracetam 

Keppra

piracetam 

Nootropil

pregabalin

Lyrica

sodium valproate 

Epilim, Episenta

stiripentol

Diacomit

tiagabine

Gabril

vigabatrin

Sabril

zonisamide

Zonegran

Lamotrigine - a special case

Lamotrigine (Lamictal) is a non-enzyme-inducing AED. But unlike other non-enzyme-inducing AEDs, it needs special consideration.

There is no evidence that the Pill affects epilepsy directly, but there is evidence that the Pill lowers lamotrigine levels in the blood. This could reduce seizure control and lead to seizures happening.

Research suggests that lamotrigine can lower the amount of progestogen from the combined oral contraceptive pill in the blood, but not the oestrogen. However, there is currently no conclusive evidence that lamotrigine reduces the effectiveness of the Pill.

If you take lamotrigine, it is important to talk to your doctors before starting any contraception that contains the hormones progestogen and oestrogen.  

What is best for me?

You may want to talk to your neurologist of a family planning advisor about the combination of AEDs and contraception that is best for you.

Below we cover different methods of contraception and how well they work alongside AEDs. When we refer to types of contraception as 'being effective' or not, this means effective in preventing pregnancy.

Further information on contraception is available from Family Planning Association (FPA) (opens new window) and NHS Choices (opens new window).

The combined oral contraceptive pill – ‘the Pill'

The combined oral pill contains the hormones oestrogen and progestogen. For any woman there are risk factors such as age, weight, high blood pressure and smoking that can cause side effects with taking the Pill.

Some AEDs can affect how well the Pill works:

  • non-enzyme-inducing AEDs do not affect the Pill so it can be a good type of contraception to use

  • enzyme-inducing AEDs cause the hormones in the Pill to be broken down more quickly, so the Pill may not be effective.

If you are taking an enzyme-inducing AED, your doctor may advise you to take a double dose of the Pill with 30µg (micrograms) of oestrogen (so that you take 60µg of oestrogen in total), especially if the Pill is your only method of contraception.

Even with a higher dose, the Pill on its own may not be completely effective in preventing pregnancy. It is often best to use other methods of contraception as well, such as a barrier method.

If you bleed between your periods, it may mean that the dose of oestrogen is not high enough to prevent pregnancy. Your doctor can advise you what to do if this happens.

Oestrogen can have a pro-convulsant (seizure-causing) effect in some women. So when a woman’s levels of oestrogen are high, there may be a higher risk of seizures happening. Taking the Pill can further increase your levels of oestrogen but your body gets rid of the oestrogen from the Pill quickly so this doesn’t make you more likely to have seizures.   

The progesterone-only pill – the ‘mini pill'

The mini pill is less effective against pregnancy than the combined pill, particularly if you take enzyme-inducing AEDs. Therefore the mini pill is not recommended as a form of contraception if you take enzyme-inducing AEDs.                  

Emergency contraception

The morning-after pill

The ‘morning-after’ pill is a type of emergency contraception that is taken after unprotected sex. It can be prescribed by GPs, pharmacists and family planning clinics.

If you take enzyme-inducing AEDs, this may reduce the effectiveness of the morning-after pill in preventing pregnancy. So you will need double the dose of the morning-after pill than other women (two pills rather than one).

As a pharmacist or clinic may not know your medical history, telling them that you take AEDs will help them give you the right dose.

Emergency intrauterine device or coil

A different type of emergency contraception is the emergency intrauterine device (IUD).  The IUD is not affected by taking AEDS. This IUD is placed inside the womb to prevent pregnancy and needs to be fitted by a trained doctor or nurse.  

Contraceptive implants

Contraceptive implants, contain progestogen and are implanted under the skin in the upper arm. Implants can be affected by enzyme-inducing AEDs so they are not recommended if you take enzyme-inducing AEDs. 

The contraceptive patch

The contraceptive patch contains oestrogen and progestogen and so works in a similar way to the combined pill. Like the combined pill, it may not be an effective form of contraception if you take enzyme-inducing AEDs.       

The vaginal ring

The vaginal ring is a flexible plastic ring that is inserted into the vagina. It works by releasing oestrogen and progesteron over 21 days. The vaginal ring may not be an effective form of contraception on its own if you take enzyme-inducing AEDs.

Methods not affected by AEDs

The following methods of contraception do not affect, and are not affected by, AEDs.         

Barrier methods

Barrier methods of contraception create a physical barrier against becoming pregnant. They include condoms, femidoms, caps and diaphragms, and are not affected by AEDs. However, for any woman, barrier methods on their own may not be effective in preventing pregnancy, and you may be advised to use them along with another contraceptive method.            

Intrauterine devices (IUDs)

IUDs are devices that are fitted into the womb. IUDs are not affected by AEDs because they do not contain hormones.           

Intrauterine systems (IUSs)

IUSs are devices fitted into the womb. Unlike IUDs, IUSs contain the hormone progestogen. An example of an IUS is the Mirena coil, which contains a slow-release progestogen called levonorgestrel.

Although IUSs contain progestogen, they are not affected by AEDs because the hormone is released straight into the womb, rather than travelling around the body where an enzyme-inducing AED can cause it to break down more quickly.

There is a risk that a woman could have a seizure while the IUS is being inserted. This is rare, and the risk is low. If you are concerned about having an IUS fitted, you can discuss this with your doctor.            

Contraceptive injections

Contraceptive injections, such as Depo Provera, contain progestogen and are given at regular intervals. Although they contain progestogen, they are not affected by AEDs because they are broken down in the blood, rather than in the liver where they could be affected by enzyme-inducing AEDs.

Taken from our Women leaflet. Order this leaflet from our online shop as part of our 'first five free' offer.

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