Blog entry by Rcgp Learning
Epilepsy is a common neurological disorder, with an estimated 87 people diagnosed in the UK every day (1). The clinical aspects of epilepsy are predominantly dealt with in secondary care but GPs may still be asked for practical advice from those living with the condition. Something that women may approach their GP about, for example, is advice on the methods of contraception available to them, and the potential risks involved when using these alongside their anti-epileptic drugs (AEDs).
It is recommended in the SIGN clinical guideline 143 on ‘Diagnosis and management of epilepsy in adults’, that advice about contraceptive methods should ideally be given to women with epilepsy before they become sexually active (2). However, to be able to do this, it’s important that GPs have access to the latest guidance on AEDs, and the possible drug interactions that could occur when using hormonal contraception.
For women with epilepsy, the advice they are given on hormonal contraception depends on the type of AED they are taking. AEDs can be separated into enzyme-inducing and non-enzyme inducing drugs, which can have different interactions when combined with hormonal contraception. The most common enzyme-inducing AEDs are carbamazepine, phenytoin, phenobarbital, primidone and topiramate.
Those taking enzyme-inducing drugs can be at risk if they are using any form of combined hormonal contraception. If the patient takes the combined oral contraceptive pill (COCP), they have more likelihood of breakthrough bleeding and contraceptive failure due to accelerated oestrogen metabolism. Enzyme-inducing drugs also increase progesterone metabolism, therefore it is recommended to avoid prescribing the progesterone-only oral contraceptive (POP) and progesterone implants. Progestogen injections and the levonorgestrel intrauterine system can be used, but patients should be made aware that the progestogen injection is associated with a reduction in bone density (2). In terms of emergency contraception, patients can choose between a copper intrauterine device (Cu-IUD) or a double dose of the levonorgestrel ‘morning after pill’ (2 x 1.5 mg tablet). Ullipristal emergency contraception is not suitable for use in women taking any enzyme-inducing anti-epileptics (2).
According to the Faculty of Sexual Reproductive Healthcare (FSRH), although lamotrigine is not thought to be an enzyme inducer, oral forms of contraception are not recommended due to potential interactions with the drug (3). Lamotrigine levels can be affected by combined hormonal contraceptives, causing a reduction in lamotrigine exposure, leading to reduced seizure control and the risk of toxicity in the hormone-free week. Conversely, the POP may increase lamotrigine levels.
Whilst sodium valproate is not an enzyme inducer, it carries a high risk of developmental disorders (four in 10) and birth defects (one in 10) when taken in pregnancy, so effective contraception is required (4). The progestogen-only implant, the progestogen-only injectable and intrauterine contraceptives are recommended options because they are less user-dependent than other methods and provide the best protection with 'typical' use (5).
The FSRH states that women with epilepsy can be reassured that the efficacy of both intrauterine contraception (Cu-IUD and LNG-IUS) and injectable contraception (DPMA) are not affected by any AED interactions (3). A full list of AEDs and recommended contraception methods can be found in the SIGN clinical guideline 143. For up to date information on potential interactions, you can refer to the online drug interaction checker on the Medscape website.
To find out more about patients living with epilepsy, please visit the Epilepsy Action website. From here, you can also read about Epilepsy Awareness Week, which runs from 14th – 20th May 2017. For further information on epilepsy or contraception, the RCGP also offers the following FREE eLearning courses:
Sudden Death in Epilepsy (SUDEP) and Seizure Safety - 0.5 CPD hours
Contraception – 1 CPD hour
RCGP members can also access the following resources on Epilepsy:
(1) Epilepsy Action. What is Epilepsy? [Internet] Available from: https://www.epilepsy.org.uk/info/what-is-epilepsy
(2) Scottish Intercollegiate Guidelines Network (SIGN). Diagnosis and management of epilepsy in adults. Edinburgh: SIGN; 2015. (SIGN publication no. 143). [May 2015]. Available from: http://www.sign.ac.uk
(3) Faculty of Sexual Reproductive Healthcare (FRSH). Clinical Guidance: Drug Interactions with Hormonal Contraception. [January 2017] Available from: https://www.fsrh.org/standards-and-guidance/documents/ceu-clinical-guidance-drug-interactions-with-hormonal/drug-interactions-final-15feb.pdf
(4) Medicines and Healthcare products Regulatory Agency. Toolkit on the risk of valproate medicines in female patients. [February 2016]. Available from: https://www.gov.uk/government/publications/toolkit-on-the-risks-of-valproate-medicines-in-female-patients
(5) Faculty of Sexual Reproductive Healthcare (FRSH). Statement from the Clinical Effectiveness Unit: Sodium Valproate and Pregnancy Risks. [February 2016]. Available from: https://www.fsrh.org/standards-and-guidance/documents/ceustatementsodiiumvalproate/ceustatementsodiiumvalproate.pdf