Mefenamic Acid

About Mefenamic Acid

• Mefenamic acid is taken to provide pain relief
• It can also help to reduce swelling
• Mefenamic acid is commonly used to treat period pain, heavy periods, or pain associated with arthritis
• Mefenamic acid is sometimes known by its brand name Ponstan
• Mefenamic acid should be taken with food
• Mefenamic acid is not suitable for everyone, including those with stomach ulcers or asthma
• It is important to read the patient leaflet for a full list of side effects and cautions.

How Does Mefenamic Acid Work?

Prostaglandins are produced by the body, but they cause pain and inflammation at the site of an injury or damage. Mefenamic acid prevents prostaglandins from being made by blocking cyclo-oxygenase (COX) enzymes. Taking mefenamic acid therefore blocks the biological pathway that causes pain and swelling.

Prostaglandins can cause heavy periods and period pain. Mefenamic acid reduces the prostaglandins produced in the lining of the uterus, and can therefore help to make periods lighter and less painful.

How is Mefenamic Acid Taken?

Mefenamic acid is a tablet that should be swallowed with some water. It should be taken at mealtimes or after food, as this helps to reduce the risk of gastric irritation or stomach ulcer formation.

Dosage of Mefenamic Acid

Each tablet contains 500mg of mefenamic acid. The usual dose is one tablet taken three times daily.

For painful periods, mefenamic acid should be started on the first day of bleeding and then reduced as the cramps and heavy bleeding begin to settle.

Are there any Side Effects?

Like all medications, mefenamic acid can have some side effects. The most common side effects include:

• Digestive complaints including indigestion, diarrhoea, stomach pain, and heartburn
• Nausea or vomiting (feeling sick or being sick)
• Changes to blood cells on blood testing
• Allergic reactions including rashes
• Mouth ulcers.

These side effects are likely to settle down, but if they persist or become troublesome you should speak to your doctor for further advice.

Serious allergic reactions happen very rarely. If you have a severe allergic reaction (anaphylaxis) including breathlessness, lip swelling or tongue swelling, call 999 immediately.

Mefenamic Acid Warnings

Mefenamic acid may not be suitable for everyone. You should tell your prescriber if you:

• Have asthma
• Have a stomach or duodenal ulcer
• Have inflammatory bowel disease (including Crohn’s disease or ulcerative colitis)
• Have liver or kidney disease
• Have heart or circulatory disease
• Have a blood clotting disorder
• Have epilepsy
• Have diabetes
• Have high cholesterol
• Have lupus (SLE or systemic lupus erythematosus)
• Have porphyria
• Are pregnant, trying to conceive, or breastfeeding.

Some medications can interact with mefenamic acid. You may be advised that mefenamic acid will not suit you if you already take:

• Warfarin or an anti-platelet medication
• Lithium
• Another type of NSAID pain relief
• Certain antidepressants
• Medication for hypertension (high blood pressure) or heart disease
• Diuretics (water tablets)
• Ciclosporin
• Steroids
• Medication for diabetes
• Methotrexate
• Mifepristone (taken to end a pregnancy)
• Certain antibiotics
• Tacrolimus
• Medications for HIV or AIDS.

Because mefenamic acid may not suit everyone, we will complete a Consultation with you including a health questionnaire. This will ensure that the medication will be suitable for you.

A qualified prescriber will review your current medications, including any herbal remedies or supplements, to ensure that mefenamic acid will not interact with them. 

Once prescribed, mefenamic acid will be ordered on your behalf via electronic prescription. Mefenamic acid will then be conveniently dispatched from one of our partner pharmacies.