For older people and frail people, the long-term benefit of medicines reduces and the potential for harm from adverse effects increases. When the benefit–risk balance changes in this way, medicine review and optimisation are important to simplify the therapeutic regimen, reduce inappropriate medicines and minimise risks. In this article, pharmacist prescriber Linda Bryant uses two case studies to illustrate important considerations during medicine reviews
An interaction between lamotrigine and combined oral contraceptives
+Practice
Pharmacotherapy
An interaction between lamotrigine and combined oral contraceptives
Tuesday 15 April 2025, 12:25 AM

Combined oral contraceptives can decrease the serum concentration of lamotrigine by 40 to 60 per cent [Image: Reproductive Health Supplies Coalition on Unsplash]
Pharmacist prescribers Linda Bryant, Penny Clark and Leanne Te Karu review a potentially significant drug–drug interaction between the antiepileptic lamotrigine and combined oral contraceptives
Key points, Combined oral contraceptives reduce lamotrigine serum levels, which can lead to decreased seizure control in the active hormone phase and/or increased, Pract Green w Pale Yellow
Kia ora and welcome to New Zealand Doctor Rata Aotearoa
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References
- Gaffield ME, Culwell KR, Lee CR. The use of hormonal contraception among women taking anticonvulsant therapy. Contraception 2011;83(1):16–29.
- Perucca E. Clinically relevant drug interactions with antiepileptic drugs. Br J Clin Pharmacol 2006;61(3):246–55.
- Reddy DS. Clinical pharmacokinetic interactions between antiepileptic drugs and hormonal contraceptives. Expert Rev Clin Pharmacol 2010;3(2):183–92.
- Reimers A, Helde G, Brodtkorb E. Ethinyl estradiol, not progestogens, reduces lamotrigine serum concentrations. Epilepsia 2005;46(9):1414–17.
- Sidhu J, Job S, Singh S, Philipson R. The pharmacokinetic and pharmacodynamic consequences of the co-administration of lamotrigine and a combined oral contraceptive in healthy female subjects. Br J Clin Pharmacol 2006;61(2):191–99.
- The Faculty of Sexual and Reproductive Healthcare. Clinical Guidance: Drug Interactions with Hormonal Contraception. May 2022.