Estrogen HRT and Lamotrigine: What the Interaction Warning Means

If you have found an interaction warning while looking into menopause treatment, you may wonder whether you have to choose between prescriptions. Take that concern to the people prescribing them and ask for one coordinated plan.

What the regulator reviewed

In its March 2024 update, New Zealand’s Medsafe² reported a potential interaction between estrogen-based HRT and reduced lamotrigine blood levels. The committee described the evidence as limited but the interaction as biologically plausible. Possible consequences included increased seizure frequency and mood instability, so it recommended warnings in estrogen-HRT data sheets, excluding vaginal preparations.²

This warning identifies a prescribing question. It does not establish what will happen to you or supply a dose adjustment to use yourself.

Bring the exact products into the conversation

Ask the pharmacist or prescriber to check your lamotrigine and the specific proposed HRT product together. Take the names, doses and how you use them, including any vaginal hormone product. Ask which clinician will coordinate the review if different services prescribe the two medicines.

You might say: “I take lamotrigine and I am considering HRT. I have read about a possible interaction. What does that mean for my prescription, and how will we review it?” These are example words to adapt.

Do not assume the exclusion of vaginal preparations in this particular warning settles the suitability of your product. Have the team check the actual prescription.

Clarify what you should report

Ask what changes in seizure control or mood should prompt contact, who to call and whether any monitoring is appropriate for you. Record the agreed contact route and review date. Tell the team about changes you have already noticed without deciding that HRT caused them.

If HRT is already prescribed, ask for advice before making changes to either medicine. A warning found online cannot replace the instructions for your own treatment.

The NHS¹ advises telling the clinician about other medicines, herbal remedies, vitamins and supplements when taking lamotrigine. Bring the complete list, rather than only the two prescriptions that started this discussion.¹

Leave with instructions you can follow

Ask the team to put any agreed prescription changes and review arrangements in writing. Read them back if the timing is unclear, and make sure both prescribing services receive the plan.

My Body Changed. Now What? includes a Visit Brief and a symptom diary. They can help you collect questions and observations for the coordinated review. See the book.