Mefenamic acid is a medicine called a non-steroidal anti-inflammatory drug (also known as an NSAID).
Tell your doctor if you have ever had an allergic reaction to any other anti-inflammatory painkiller.
Take your doses after a meal, or with a snack.
About mefenamic acid
|Type of medicine||Non-steroidal anti-inflammatory drug (NSAID)|
|Used for||Relief of pain and inflammation in adults and children over 12 years of age|
|Available as||Capsules, tablets, oral liquid medicine|
Anti-inflammatory painkillers like mefenamic acid are sometimes called non-steroidal anti-inflammatory drugs (NSAIDs), or just 'anti-inflammatories'. Mefenamic acid is used to treat painful conditions such as arthritis, pain associated with heavy menstrual bleeding, and pain after surgical operations.
Mefenamic acid works by blocking the effect of chemicals called cyclo-oxygenase (COX) enzymes. These enzymes help to make other chemicals in the body, called prostaglandins. Some prostaglandins are produced at sites of injury or damage, and cause pain and inflammation. By blocking the effect of COX enzymes, fewer prostaglandins are produced, which means pain and inflammation are eased.
Before taking mefenamic acid
Some medicines are not suitable for people with certain conditions, and sometimes a medicine may only be used if extra care is taken. For these reasons, before you start taking mefenamic acid, it is important that your doctor knows:
- If you have asthma or any other allergic disorder.
- If you have ever had a stomach or duodenal ulcer, or if you have an inflammatory bowel disorder such as Crohn's disease or ulcerative colitis.
- If you are pregnant, trying for a baby, or breast-feeding.
- If you are over 65 years of age.
- If you have liver or kidney problems.
- If you have a heart condition, or a problem with your blood vessels or circulation.
- If you have high blood pressure.
- If you have ever had blood clotting problems.
- If you have epilepsy.
- If you have a connective-tissue disorder, such as systemic lupus erythematosus (an inflammatory condition also called lupus, or SLE).
- If you have a rare inherited blood disorder called porphyria.
- If you are taking any other medicines. This includes any medicines you are taking which are available to buy without a prescription, such as herbal and complementary medicines.
- If you have ever had an allergic reaction to any other NSAID (such as aspirin, ibuprofen, diclofenac, and indometacin), or to any other medicine.
How to take mefenamic acid
- Before you start taking mefenamic acid, read the manufacturer's printed information leaflet from inside the pack. The manufacturer's leaflet will give you more information about the medicine and provide a full list of side-effects which you may experience from taking it.
- Take mefenamic acid exactly as your doctor tells you to. The usual dose is 500 mg, which is taken as two 250 mg capsules, or one 500 mg tablet. You will be asked to take this dose three times a day. If you are taking it for period pain, your doctor will likely suggest that you take it for a few days each month, starting on your first day of bleeding.
- Take your doses with a meal or after a snack, as this can help prevent unwanted side-effects such as indigestion.
- If you forget to take a dose, take it as soon as you remember unless it is nearly time for your next dose, in which case leave out the missed dose. Do not take two doses together to make up for a missed dose.
Getting the most from your treatment
- Your doctor will try to prescribe you mefenamic acid for the shortest time possible to reduce the risk of side-effects. If you need to take it over a long period of time, your doctor may want to prescribe another medicine along with it to protect your stomach from irritation.
- Try to keep any regular appointments with your doctor. This is so your doctor can check on your progress. It is especially important if you are taking mefenamic acid for a long-term condition.
- If you have asthma, symptoms such as wheeze or breathlessness can be made worse by anti-inflammatories. If this happens to you, you should stop taking mefenamic acid and see your doctor as soon as possible.
- If you buy any medicines, check with a pharmacist that they are safe to take with mefenamic acid.
- If you are having an operation or dental treatment, tell the person carrying out the treatment which medicines you are taking.
Can mefenamic acid cause problems?
Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. The table below contains some of the most common ones associated with mefenamic acid. You will find a full list in the manufacturer's information leaflet supplied with your medicine. The unwanted effects often improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any of the following continue or become troublesome.
|Common mefenamic acid side-effects
||What can I do if I experience this?|
|Indigestion, heartburn, abdominal discomfort||Remember to take your doses with a meal or after a snack. If the discomfort continues, speak with your doctor|
|Feeling or being sick||Stick to simple meals. Drink plenty of liquid to replace any lost fluids|
|Diarrhoea, mouth ulcers||Stop taking mefenamic acid and let your doctor know as soon as possible|
Important: if you experience any of the following less common but possibly serious symptoms, stop taking mefenamic acid and contact your doctor for advice straightaway:
- If you have any breathing difficulties such as wheeze or breathlessness.
- If you have any signs of an allergic reaction such as swelling around your mouth or face, or an itchy skin rash.
- If you have severe diarrhoea, pass blood or black stools, vomit blood, or have abdominal pains.
If you experience any other symptoms which you think may be due to this medicine, speak with your doctor or pharmacist.
How to store mefenamic acid
- Keep all medicines out of the reach and sight of children.
- Store in a cool, dry place, away from direct heat and light.
Important information about all medicines
Never take more than the prescribed dose. If you suspect that you or someone else might have taken an overdose of this medicine, go to the accident and emergency department of your local hospital. Take the container with you, even if it is empty.
This medicine is for you. Never give it to other people even if their condition appears to be the same as yours.
Do not keep out-of-date or unwanted medicines. Take them to your local pharmacy which will dispose of them for you.
If you have any questions about this medicine ask your pharmacist.
Further reading & references
- Manufacturer's PIL, Mefenamic Acid 250 mg Capsules; Amdipharm Mercury Company Limited, The electronic Medicines Compendium. Dated October 2012.
- British National Formulary; 66th Edition (September 2013) British Medical Association and Royal Pharmaceutical Society of Great Britain, London
Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.
Dr Adrian Bonsall