Mefenamic Acid

What is Mefenamic acid?

Mefenamic acid is one of the group of medicines called non-steroidal anti-inflammatory drugs. It is used to relieve many different kinds of pain or discomfort but primarily for relief of period pain. It can also be prescribed to women after childbirth.

How does Mefenamic acid work?

Mefenamic acid contains an active ingredient which targets the pain or inflammation in your body to relive it.

What are the benefits of taking Mefenamic acid?

Periods vary from woman to woman but for some women, they can be an extremely uncomfortable and painful experience that last for a prolonged amount of time.

Taking Mefenamic acid to relieve this pain allows women to go about their daily life, whatever stage of their menstrual cycle they’re in.

How do I use Mefenamic acid?

Mefenamic acid is a prescription-only medication. Always follow the advice of your doctor and read the patient information leaflet provided in the medication packet.

Swallow the tablets whole with a drink of water - do not crush or chew them. It’s recommended to take these tablets during or just after a meal, and your dose will be decided upon by your doctor, based on the type and severity of the condition you’re trying to treat.

Mefenamic acid dosage

Mefenamic acid contains an active anti-inflammatory ingredient, and the tablets or capsules come in various doses. The normal dose for adults is 500mg, taken 3 times a day (1500mg in total), however doctors often prescribe a lower amount for adults aged 70 years or over.

If you take more Mefenamic acid than you should, then you should contact your doctor immediately and be aware that you may experience side effects. If you forget to take it, then take it as soon as you remember, provided it is not too close to the time of your next dose. You should never double up on your dose to make up for a forgotten one.

Side effects & precautions

Before taking Mefenamic acid, you should always first consult your doctor. You should not take Mefenamic acid if any of the following apply to you:

• Have a history of stomach bleeding or perforation which may be related to the use of NSAIDs (naproxen, ibuprofen, diclofenac) or aspirin
• Are allergic to mefenamic acid or any other ingredients of this medicine
• Have a history of allergy to aspirin, ibuprofen or NSAIDs,
• Have a history of, or active disorders of the stomach or intestines such as ulcerative colitis, Crohn’s disease, gastrointestinal cancers or diverticulitis
• Have severe heart failure
• Have severe liver or kidney failure
• Are in the last three months of your pregnancy
• Have recently had coronary artery bypass graft surgery
• Are taking aspirin or other non-steroidal anti-inflammatory drugs for pain relief e.g. naproxen, diclofenac
• Are taking anticoagulants such as warfarin to prevent blood clots.

Your prescription of Mefenamic acid may also be affected by a number of other factors, so you should make your doctor aware if any of the following apply:

• Suffer from asthma or have had a history of asthma
• Are an older person
• Have ulcerative colitis or Crohn’s disease
• Have systemic lupus erythematosus (SLE)
• Are known to be a poor metaboliser of CYP2C9
• Suffer from kidney disease and dehydration
• Suffer from liver disease
• Have diabetes
• Have heart problems, previous stroke or think you might be at risk of these conditions
• Regularly take a painkiller for headaches over a prolonged period
• Have a bleeding disorder or if you are going to have a major operation
• Have epilepsy
• Are taking any other NSAIDs (e.g. ibuprofen, diclofenac)
• Are taking any other anti-inflammatory medicines including steroids
• Are taking aspirin or medicines that thin the blood
• Are taking antidepressants called selective serotonin re-uptake inhibitors
• Have a problem with the metabolism of sugar in your body

Like many medications with active ingredients, Mefenamic acid can affect or be affected by other medicines. Particular medications that you may experience this with include the following:

• Low dose aspirin (75mg) to help prevent heart attack or stroke
• Corticosteroids,
• Certain medicines used to treat heart conditions known as cardiac glycosides
• Certain medicines for depression such as lithium
• Antihypertensives and ACE inhibitors, used to treat high blood pressure
• Methotrexate
• Cyclosporin
• Quinolone antibiotics
• Mifepristone
• Diuretics such as hydrochlorothiazide
• Anti-platelet agents (used to prevent blood clots)
• Tacrolimus which is used to suppress the immune system
• Zidovudine which is used in the treatment of AIDS and HIV infection
• Aminoglycoside antibiotics
• Probenecid used in the treatment of gout
• Some diabetic medicines such as (e.g. glipizide, glibenclamide).

If you are taking any of the above medications, then you should make your doctor aware so that they can advise whether or not Mefenamic acid will be the best course of action for you.

If you are pregnant then you should consult your doctor before taking Mefenamic acid. It is definitely not suitable for those in the last 3 months of pregnancy, but affects on the baby in the first 6 months are not known. This means it’s not usually recommended but your doctor may prescribe it you if they feel it necessary. However, you should not take Mefenamic acid if you are trying to get pregnant, as the drug will make it more difficult.

If you are breastfeeding then you should be aware that Mefenamic acid can be passed into your breast milk and should therefore not be taken during this time unless expressly instructed to do so by your doctor.

The most common side effects of using Mefenamic acid include:

• Diarrhoea or constipation, wind
• Feeling sick (nausea), vomiting, loss of appetite
• Sore mouth and/or lips
• Stomach ache, indigestion, abdominal pain/discomfort
• Blood in the stools or urine
• Oily stools
• Inflammation of the pancreas, stomach, small intestine or colon

If you do experience one or more of these side effects and they persist or worsen, then inform your doctor right away. You should also contact your doctor immediately if you experience any serious side effects, such as vomiting blood, severe skin reaction, or difficulty breathing.