Health Canada Endorsed Important Safety Information on LAMICTAL (lamotrigine): Important Safety Information Concerning Interactions of the Anti-epileptic Drug Lamictal® and Oral Contraceptives
In September 2004, GlaxoSmithKline Inc. distributed a letter to Canadian healthcare professionals concerning the safety of the anti-epileptic drug, Lamictal®. A recently completed clinical pharmacology study demonstrated that "concomitant use of hormonal contraceptives with Lamictal® may significantly decrease serum lamotrigine levels".
The completed clinical pharmacology study reported:
· "An oral contraceptive preparation administered in combination with lamotrigine significantly decreased serum levels of lamotrigine…
· During the "pill-free" week of the oral contraceptive there was a gradual increase in trough lamotrigine serum concentrations, by approximately two fold by the end of the "pill-free" week.
· Lamotrigine had a modest effect on levonorgestrel [ingredient in the oral contraceptive] plasma concentrations…The effect on ethinylestradiol [ingredient in the oral contraceptive] concentrations was minimal.
· An increase in serum FSH and LH concentrations and a marginal increase in serum estradiol concentrations were observed during the period of co-administration of the oral contraceptive and lamotrigine
· There was no hormonal evidence of ovulation as evidenced by progesterone serum concentrations.
· GlaxoSmithKline has received a limited number of reports of break-through seizures, unexpected pregnancies and of menstrual bleeding disorders (e.g. breakthrough bleeding) occurring with the concomitant use of Lamictal® and hormonal preparations."
Overall, if Lamictal® is taken concomitantly with the oral contraceptive pill, the contraceptive may be less effective (as is the case with other anti-epileptic drugs as well) and Lamictal® may be less effective, consequently increasing the risk of pregnancy and the risk of seizures.
Maintenance doses may need to be changed for patients on Lamictal®, however they must not start or discontinue their oral contraceptives without physician approval. Adjustments to the dosage of Lamictal® will need to be adjusted if a patient is: taking or starting oral contraceptives; stopping contraceptives; or receiving other hormonal contraceptive preparations or hormone replacement therapy. Women should be advised that there have been cases of unexpected pregnancies and of menstrual bleeding disorders when using Lamictal® and hormones concurrently. A physician should be notified immediately if there are such changes in menstrual pattern (e.g., break-through bleeding)
while receiving Lamictal in combination with hormonal preparations.
Source: Health Canada. "
Health Products and Food Branch."
