Lamotrigine Interaction with Contraceptives

There is a well-known bi-directional interaction between lamotrigine and contraceptives. Contraceptives, when coadministered with lamotrigine, can decrease lamotrigine levels by up to 50%. For patients who are using this to control a seizure disorder, this puts them at a substantially increased risk of seizures. Lamotrigine can also decrease the efficacy of progestins. For women who are on the progestin-only contraceptives such as the mini-pill or Mirena IUD, they are at a risk of contraceptive failure. It has not been fully established whether or not there is a risk of contraceptive failure on combination hormonal products, so patients are advised to use other methods of contraceptives (diaphragm, condoms) while taking lamotrigine.

For patients who were on lamotrigine prior to initiating birth control, they will require an increase in dose. For patients who were already on birth control prior to starting the lamotrigine, this interaction is less of a safety concern. In this scenario, doctors will have to gradually taper up to the effective dose for the patient. It is important to note that patients on birth control may require higher-than-normal doses of lamotrigine. Also, doctors must be aware that they will likely have to decrease the dose of lamotrigine if the patient decides to stop using their birth control.

1 Lexicomp Drug Interactions>
2 .Micromedex Drug Interactions
3. Facts & Comparisons Drug Interactions
4. Oral Contraceptives Reduce Lamotrigine (Lamictal) Blood Levels <link>