Mefenamic acid (Ponstan)
How does it work?
Ponstan capsules contain the active ingredient mefenamic acid, which is a type of medicine called a non-steroidal anti-inflammatory drug (NSAID). NSAIDs are used to relieve pain and inflammation. Mefenamic acid is also available without a brand name, ie as the generic medicine.
Mefenamic acid works by blocking the action of a substance in the body called cyclo-oxygenase (COX). Cyclo-oxygenase is involved in the production of various chemicals in the body, some of which are known as prostaglandins. Prostaglandins are produced by the body in response to injury and certain diseases and conditions, and cause pain, swelling and inflammation. Mefenamic acid blocks the production of these prostaglandins and is therefore effective at reducing inflammation and pain.
Mefenamic acid may also work by preventing the action of prostaglandins after they have already been formed.
Mefenamic acid is used to relieve pain and inflammation in a wide range of musculoskeletal conditions, including rheumatoid arthritis, muscular pain and traumatic pain such as sprains and fractures. It can also be used to relieve other types of pain, such as toothache, headaches and pain following surgery or childbirth.
Mefenamic acid is also useful for heavy and painful menstrual periods, in addition to its general painkilling properties. This is because period pain cramps are caused by the production of prostaglandins by the lining of the womb and prostaglandin production is known to be increased in women who suffer from heavy periods. By opposing the production and action of prostaglandins, mefenamic acid relieves period pains and also reduces blood loss in women who have heavy periods.
What is it used for?
- Painful periods (dysmenorrhoea).
- Abnormally heavy periods (menorrhagia).
- Rheumatoid arthritis.
- Juvenile arthritis (Still's disease).
- Muscular pain.
- Pain and inflammation due to accidents, such as sprains, strains, fractures.
- Pain following childbirth.
- Pain following surgery.
- This medicine should be taken with or after food to help reduce irritation to the stomach.
- If you get diarrhoea while taking this medicine you should stop taking it and consult your doctor. Your doctor may decide that you should not take this medicine again.
- Your doctor will prescribe you the lowest effective dose of this medicine for the shortest possible time necessary to relieve your symptoms. This is to minimise the chances of any side effects, particularly those mentioned below. It is important not to exceed the prescribed dose.
- NSAIDs can occasionally cause serious side effects on the gut, such as ulceration, bleeding or perforation of the stomach or intestinal lining. This type of side effect is more likely to occur in elderly people and in people taking high doses of the medicine. The risk can also be increased by taking certain other medicines (see below). It is important that these people, as well as people with a history of disorders affecting the stomach or intestines, are closely monitored by a doctor while taking this medicine. If your doctor thinks you are at high risk of side effects on the gut you may be prescribed an additional medicine to help protect your gut. All people taking this medicine should stop treatment and consult their doctor immediately if they experience any sign of bleeding from the stomach or intestine during treatment, for example vomiting blood and/or passing black/tarry/bloodstained stools.
- Studies have suggested that use of some NSAIDs may be associated with a small increase in the risk of heart attacks and stroke (particularly if used in high doses or for long periods of time). If you have risk factors for heart disease or stroke, such as diabetes, high blood pressure, high cholesterol or smoking, your doctor will need to assess the overall benefits and risks before deciding if this medicine is suitable for you. Ask your doctor or pharmacist for further information.
- Very rarely, NSAIDS may cause serious blistering or peeling skin reactions (eg Stevens-Johnson syndrome, toxic epidermal necrolysis, exfoliative dermatitis). For this reason, you should stop taking this medicine and consult your doctor if you get a skin rash or sores inside your mouth while taking this medicine. This side effect is very rare, but if it occurs, is most likely to happen in the first month of treatment.
- During long-term treatment with this medicine you should have regular check-ups with your doctor so that you can be monitored for possible side effects of the medicine. This might include routine blood tests to monitor your kidney function, liver function and levels of blood components, particularly if you are elderly.
- If you have heart failure, liver disease or kidney disease, you are taking diuretic medicines, or you are recovering from major surgery, your kidney function should be assessed before starting and regularly throughout treatment with this medicine.
- This medicine may mask the signs and symptoms of infection, such as fever and inflammation. This may make you think mistakenly that an infection is getting better when it isn't, or that an infection is less serious than it is. For this reason you should tell your doctor if you get an infection while you are taking this medicine.
Use with caution in
- Elderly people.
- History of disorders affecting the stomach or intestines.
- Decreased liver function.
- Decreased kidney function.
- Heart failure.
- High blood pressure (hypertension).
- Heart disease caused by inadequate blood flow to the heart (ischaemic heart disease), eg angina or history of heart attack.
- Disease of the blood vessels in and around the brain (cerebrovascular disease), eg history of stroke or mini-stroke (TIA).
- Poor circulation in the arteries of the legs or feet (peripheral arterial disease).
- Raised levels of fats such as cholesterol in the blood (hyperlipidaemia).
- History of allergies.
- History of asthma.
- People with blood clotting disorders or taking anticoagulant medicines.
- Diseases affecting connective tissue, eg systemic lupus erythematosus.
- Hereditary blood disorders called porphyrias.
Not to be used in
- People in whom aspirin or other NSAIDs, eg ibuprofen, cause allergic reactions such as asthma attacks, itchy rash (urticaria), nasal inflammation (rhinitis) or swelling of the lips, tongue and throat (angioedema).
- People with an active peptic ulcer or bleeding in the gut.
- People who have had recurrent peptic ulcers or bleeding in the gut (two or more episodes).
- People who have experienced bleeding or perforation in the gut as a result of previous treatment with an NSAID.
- Inflammatory bowel disease such as ulcerative colitis or Crohn's disease.
- Severe heart failure.
- Severe liver failure.
- Severe kidney failure.
- Third trimester of pregnancy.
- Relieving pain following coronary artery bypass graft (CABG) surgery.
- Rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption (Ponstan capsules contain lactose).
This medicine should not be used if you are allergic to any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.
If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.
Pregnancy and breastfeeding
Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.
- This medicine is not recommended for use in pregnancy unless considered essential by your doctor. This is particularly important in the first and third trimesters. If taken in the third trimester it may delay labour, increase the length of labour and cause complications in the newborn baby. Some evidence suggests that NSAIDs should also be avoided by women attempting to conceive, as they may temporarily reduce female fertility during treatment and may also increase the risk of miscarriage or malformations. Seek medical advice from your doctor.
- This medicine may pass into breast milk in small amounts. The manufacturer states that it should not be used by breastfeeding mothers. Seek medical advice from your doctor.
- Take this medication with or after food.
Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Just because a side effect is stated here, it does not mean that all people using this medicine will experience that or any side effect.
- Disturbances of the gut such as indigestion, diarrhoea, constipation, nausea, vomiting or abdominal pain (see warning section above).
- Ulceration or bleeding in the stomach or intestines (see warning section above).
- Skin reactions such as rashes or itching.
- Visual disturbances.
- Sensation of spinning (vertigo).
- Sensation of ringing, or other noise in the ears (tinnitus).
- Pins and needles sensations.
- Retention of fluid in the body tissues, resulting in swelling (oedema).
- Increased blood pressure.
- Awareness of your heartbeat (palpitations).
- Inflammation of the pancreas (pancreatitis).
- Allergic reactions such as severe skin rashes, swelling of the lips, tongue and throat (angioedema) or narrowing of the airways (bronchospasm).
- Kidney, liver or blood disorders.
The side effects listed above may not include all of the side effects reported by the medicine's manufacturer.
For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.
How can this medicine affect other medicines?
It is important to tell your doctor or pharmacist what medicines you are already taking, including those bought without a prescription and herbal medicines, before taking this medicine. Similarly, check with your doctor or pharmacist before taking any new medicines while taking this one, to make sure that the combination is safe.
Mefenamic acid should not be used in combination with painkilling doses of aspirin or any other NSAID taken by mouth, eg ibuprofen, as this increases the risk of side effects on the stomach and intestines. Selective inhibitors of COX-2 such as celecoxib or etoricoxib should also be avoided for the same reason.
There may be an increased risk of ulceration or bleeding in the gut if mefenamic acid is taken with corticosteroids such as prednisolone.
There may also be an increased risk of bleeding in the gut if mefenamic acid is taken with the following medicines:
- anti-blood-clotting (anticoagulant) medicines such as warfarin or heparin
- anti-platelet medicines to reduce the risk of blood clots or 'thin the blood', eg low-dose aspirin, clopidogrel, dipyridamole
- SSRI antidepressants, eg fluoxetine, paroxetine, citalopram
There may be an increased risk of side effects on the kidneys if mefenamic acid is used with any of the following medicines:
- ACE inhibitors, eg enalapril
- angiotensin II receptor antagonists such as losartan
- diuretics, eg furosemide
Mefenamic acid may oppose the blood pressure lowering effects of certain medicines to treat high blood pressure, including the following:
- ACE inhibitors such as captopril
- angiotensin II receptor antagonists such as losartan
- beta-blockers such as propranolol
- diuretics such as furosemide.
Mefenamic acid may reduce the removal of the following medicines from the body and so may increase the blood levels and risk of side effects of these medicines. People using mefenamic acid with any of these should be closely monitored by their doctor:
If this medicine is used in combination with quinolone antibiotics, such as ciprofloxacin or norfloxacin there may be an increased risk of seizures (fits). This may occur in people with or without a previous history of epilepsy or convulsions.
Other medicines containing the same active ingredient
Mefenamic acid tablets, capsules and suspension are also available without a brand name, ie as the generic medicine.