NZ Formulary



What does it do?

Mexiletine is used to treat irregular heartbeats.

Before you start

  • Tell your doctor if you have ever had a seizure.
  • Tell your doctor if you are pregnant, planning to become pregnant, or breastfeeding.

How should you take it?

Take mexiletine regularly as directed with a glass of water.

What if you forget a dose?

If it is nearly time for your next dose, skip the missed dose and take your next dose at the usual time. Otherwise, take the missed dose as soon as you remember. Do not take two doses at the same time.

Can you take other medicines?

Tell your pharmacist or doctor about all medicines or treatments that you may be taking, including vitamins, herbal products or recreational drugs.

What side effects might you notice?

Side EffectsRecommended action

Symptoms of heart problems including: fluttering, pounding or pain in your chest, feeling your heart skips a beat, dizziness or fainting


Tell your doctor immediately

Swollen feet or legs, short of breath

Loss of co-ordination/walking or handwriting problems, tremor

Changes in vision

Tell your doctor


Tell your doctor if troublesome

Nausea, vomiting, heartburn

Take with food and tell your doctor if symptoms continue

If you notice any other effects, discuss them with your doctor or pharmacist.

Important information continues on next page.

Other information:

  • Mexiletine can impair your ability to do tasks such as driving or using machines. Alcohol makes this worse. Discuss your risk with your health professional. (search NZTA - Are you safe to drive?)
  • Smoking can change the effect of mexiletine. Tell your doctor if you give up, cut down or start smoking.
  • Mexiletine is not registered for use in New Zealand. Discuss with your doctor.