NZ Formulary

Mefenamic acid

mef-en-am-ik ass-id

What does it do?

Mefenamic acid reduces pain and inflammation.

How should you take it?

Take mefenamic acid with food and a glass of water.

What if you forget a dose?

If you take mefenamic acid regularly and 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?

Some medicines available without a prescription may react with mefenamic acid including:

  • anti-inflammatories, such as ibuprofen (e.g. Nurofen®), or aspirin (e.g. Disprin®, in doses used for pain relief). These can also be found in some cold and flu medicines (e.g. Nurofen Cold and Flu®), and creams or gels (e.g. Voltaren Emulgel®)
  • low-dose aspirin (e.g. Cartia®)

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

Stomach pain, coughing or vomiting of blood, black bowel motions

Swollen lips, tongue, throat or face, trouble breathing

Chest pain

Symptoms of liver problems including: yellow skin or eyes, itching, dark urine, pale bowel motions, abdominal pain

Easy/unusual bruising or bleeding

Tell your doctor immediately

Severe or persistent diarrhoea

Swollen feet or legs, short of breath

Bloody or cloudy pee

Ringing in the ears

Tell your doctor

Dizziness

Indigestion, nausea

Constipation or diarrhoea

Skin rash

Tell your doctor if troublesome

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

Other information:

  • Tell your doctor if you have heart, kidney, stomach or bowel problems, high blood pressure, asthma, or if you have ever had a stroke or TIA (mini-stroke).
  • Tell your doctor if you have had problems with aspirin or anti-inflammatories.
  • Tell your doctor if you are pregnant, planning to become pregnant, or breastfeeding.
  • In most cases, paracetamol and/or codeine may be safely used while taking mefenamic acid.