Lamotrigine and the contraceptive pill

• if considering lamotrigine therapy when a woman is taking oral contraceptives (1)
  • prescribers should explain that the drug may decrease the effectiveness of the contraceptive and discuss alternative methods of contraception
  • if a woman taking lamotrigine stops taking an oral contraceptive, the dose of lamotrigine may need to be reduced by up to 50%

A Faculty of Sexual and Reproductive Healthcare (FSRH) statement noted that (2):

• combined hormonal contraception (CHC) increases the clearance of lamotrigine and reduces serum lamotrigine levels
• women using lamotrigine should be advised that seizure frequency may increase when initiating CHC, and that lamotrigine side effects may increase in the pill-free interval or when discontinuing CHC
• there is evidence that progestogen-only methods do not affect lamotrigine levels
• lamotrigine levels are not reduced by CHC when lamotrigine is given in conjunction with sodium valproate
• combined hormonal contraception (CHC) is not usually recommended in women on lamotrigine monotherapy due to the risk of reduced seizure control whilst on CHC, and the potential for toxicity in the CHC-free week (3)

It has been suggested that the clearance of lamotrigine is increased by two fold in women who use an ethinylestradiol/levonorgestrel (30 µg/150 µg) pill (4)

Reference:

1. NICE (July 2006). Bipolar disorder
2. FSRH (January 2010). CEU Statement - Antiepileptic Drugs and Contraception
3. FSRH (January 2011). Drug Interactions with Hormonal Contraception
4. Royal College of Obstetricians and Gynaecologists. Faculty of Sexual and Reproductive Healthcare guideline 2011. Drug Interactions with Hormonal Contraceptions