Mefenamic acid is a medicine called a non-steroidal anti-inflammatory drug. It is also known as 'an NSAID'.
Tell your doctor if you have ever had an allergic reaction to any other anti-inflammatory painkiller.
Take mefenamic acid with food.
About mefenamic acid
|Type of medicine||A non-steroidal anti-inflammatory drug (NSAID)|
|Used for||Relief of pain and inflammation in adults and in children over 12 years of age|
|Available as||Capsules, tablets, oral liquid medicine|
Anti-inflammatory painkillers like mefenamic acid are also called non-steroidal anti-inflammatory drugs (NSAIDs), or sometimes 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 natural 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 can 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 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 have asthma or any other allergic disorder.
- If you are pregnant, trying for a baby, or breastfeeding.
- If you have any problems with the way your liver works, or if you have any problems with the way your kidneys work.
- If you have a heart condition or a problem with your blood vessels or circulation.
- If you have high blood pressure.
- If you have any blood clotting problems.
- If you have epilepsy.
- If you have high blood sugar or cholesterol levels.
- If you have a connective tissue disorder such as systemic lupus erythematosus. This is an inflammatory condition which is 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, as well as 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 the treatment, read the manufacturer's printed information leaflet from inside the pack. It will give you more information about mefenamic acid, and it will also provide you with a full list of the side-effects which you could 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 mefenamic acid with food. This will help to protect your stomach from side-effects such as indigestion.
- If you forget to take a dose, take it as soon as you remember unless your next dose is due. If your next dose is due, then take the dose which is due but leave out the forgotten one. 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.
- There is known to be a small increased risk of heart and blood vessel problems in people taking some anti-inflammatory painkillers long-term. Your doctor will explain this to you and will prescribe the lowest suitable dose for the shortest time in order to reduce the risk. Do not take more than the recommended dose.
- If you buy any medicines, check with a pharmacist that they are suitable for you to take. This is because you should not take mefenamic acid with any other anti-inflammatory painkiller, some of which are available in cold and flu remedies which can be bought 'over the counter'.
- 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 more common ones associated with mefenamic acid. The best place to find a full list of the side-effects which can be associated with your medicine, is from the manufacturer's printed information leaflet supplied with the medicine. Alternatively, you can find an example of a manufacturer's information leaflet in the reference section below. 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, wind, stomach pain||Remember to take your doses with a meal or after a snack. If the discomfort continues, speak with your doctor|
|Feeling sick (nausea) or being sick (vomiting)||Stick to simple meals. Drink plenty of liquid to replace any lost fluids|
|Diarrhoea, skin rash||Stop taking mefenamic acid and let your doctor know about this as soon as possible|
|Mouth ulcers||If troublesome, let your doctor know|
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 pass blood or black stools, bring up (vomit) blood, or have severe stomach pains.
If you experience any other symptoms which you think may be due to the medicine, speak with your doctor or pharmacist for further advice.
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 and references
Manufacturer's information for healthcare professionals (SPC), Ponstan® 250 mg Capsules; Chemidex Pharma Ltd, The electronic Medicines Compendium. Dated January 2020.
British National Formulary, 78th Edition (Sep 2019); British Medical Association and Royal Pharmaceutical Society of Great Britain, London.