What is the interaction between lamotrigine (anticonvulsant) and hormonal birth control (contraceptives)?

From the Guidelines

Lamotrigine can significantly interact with hormonal birth control methods, particularly those containing estrogen, potentially reducing the effectiveness of the contraceptive and altering lamotrigine levels, thus impacting seizure control in individuals with epilepsy. This interaction is crucial to consider in clinical practice to prevent unintended pregnancies and maintain therapeutic lamotrigine levels. According to the U.S. Medical Eligibility Criteria for Contraceptive Use, 2010 1, certain anticonvulsants, including lamotrigine, can have significant interactions with hormonal contraceptives. Specifically, the use of lamotrigine with combined oral contraceptives (COCs) can lead to decreased lamotrigine levels due to increased metabolism, potentially reducing its efficacy in seizure control.

Key considerations include:

• The potential for reduced effectiveness of hormonal contraceptives when used with certain anticonvulsants, including lamotrigine, which may increase the risk of unplanned pregnancy.
• The necessity for healthcare providers to adjust lamotrigine dosages when initiating or discontinuing hormonal contraceptives to maintain therapeutic levels and prevent breakthrough seizures.
• The recommendation for women taking lamotrigine and hormonal contraceptives to use additional non-hormonal contraceptive methods, such as condoms or intrauterine devices (IUDs), to ensure effective contraception.

It's essential to note that while lamotrigine may interact with estrogen-containing contraceptives, its interaction with progestin-only contraceptives is less clear, with some evidence suggesting no significant interaction 1. However, given the potential risks associated with reduced contraceptive efficacy and altered lamotrigine levels, careful monitoring and adjustment of medications under healthcare supervision are critical. Always informing healthcare providers about all medications being taken and not making changes without medical supervision is paramount to prevent adverse outcomes such as breakthrough seizures or unintended pregnancies.

From the Research

Interaction between Lamotrigine and Hormonal Birth Control

• The interaction between lamotrigine, an anticonvulsant, and hormonal birth control (contraceptives) is significant due to the effect of estrogens on lamotrigine serum concentrations 2, 3, 4.
• Estrogens, such as those found in hormonal contraceptives, induce the glucuronidating enzyme, leading to a decrease in lamotrigine serum concentrations by 50-60% when combined with hormonal contraceptives containing ethinyl estradiol (EE) 2.
• This reduction in lamotrigine levels can pose a risk of seizures when hormonal agents are initiated and/or toxicity during pill-free weeks 3.
• The use of non-oral hormonal contraceptive methods, such as the vaginal ring and transdermal patch, also decreases lamotrigine concentrations during the active phase of treatment 4.

Contraceptive Options for Women with Epilepsy

• Intrauterine devices (IUDs) and barrier methods do not rely on hormonal components for contraceptive efficacy and are therefore appropriate options for women using enzyme-inducing medications 3.
• A progestin-containing IUD has been shown to be a safe and acceptable long-acting contraceptive for women with epilepsy, with no significant impact on antiepileptic drug trough concentrations or seizure frequency 5.
• Injectable contraception (depot medroxyprogesterone acetate) appears effective with antiepileptic drug use, but the potential for bone mineral density loss is a concern 3.

Clinical Implications

• The reduction in lamotrigine levels due to hormonal contraceptives has important implications for contraceptive counseling and maintaining therapeutic levels in women of childbearing age with epilepsy 4, 6.
• Dose increase of lamotrigine following addition of exogenous estrogen is rare among women with epilepsy, with potential disparities based on age and income level 6.
• More guidance may be needed for providers on adjusting lamotrigine doses for women with epilepsy who are using hormonal contraceptives 6.