How Does Mefenamic acid Work?

Mefenamic acid is a type of drug called a non-steroidal anti-inflammatory drug (NSAID). It works by stopping the production of compounds called prostaglandins in the body, which have a number of effects, including to cause inflammation.

As a result, mefenamic acid can help to reduce pain and inflammation by stopping the production of prostaglandins. This is why it is usually used to relieve painful inflammatory conditions, such as period pain and heavy menstrual bleeding.

Brand Names and Doses

Mefenamic acid is the generic name of the drug, which is the name of the active component that has an effect on your body. You may also know it better by one of its brand names, Mefic or Ponstan, which are the names given to the medication made by each pharmaceutical company for marketing purposes.

Both Mefic and Ponstan are available as an oral capsule in a dose of 250 mg.

It has a relatively short half-life, which means that your body clears it quite quickly. As a result, you would need to take a dose 3 times a day to maintain a constant effect. It’s best to take each dose with food to reduce the risk of side effects, such as diarrhoea.

What type of drug is it?

Mefenamic acid is a type of drug known as a non-steroidal anti-inflammatory drug (NSAID), which is a group of drugs that all work in a similar way. Other examples of NSAIDs include:

• Aspirin

• Celecoxib

• Diclofenac

• Etoricoxib

• Ibuprofen

• Indomethacin

• Ketoprofen

• Ketorolac

• Meloxicam

• Naproxen

• Parecoxib

• Piroxicam

• Sulindac

• Tiaprofenic acid

How does Mefenamic acid work?

Mefenamic acid works by inhibiting COX-1 and COX-2, which are needed to produce the different prostaglandins in your body. You have many different types of prostaglandins in your body, and there are some in almost every tissue of your body. They each have different effects, such as to cause:

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• the tissues in your body to become inflamed

• your blood vessels to relax and widen

• the platelets in your blood to come together to form a clot

Mefenamic acid has a general effect on almost all the prostaglandins because it blocks both COX-1 and COX-2 from producing prostaglandins in your body. This means that it can reduce all of the usual effects prostaglandins. We want it to reduce inflammation because that is why we are using it, but it can also cause hypertension and affect the way the blood forms clots.

Side Effects

There are many different side effects that you may experience if you are taking mefenamic acid. These do not affect everyone, but it’s important to know what they are so that you can recognize them if you do notice them.

The side effects of mefenamic acid may include:

• Nausea​

• Heartburn (dyspepsia)

• Diarrhea

• Headache

• Dizziness

• Gastrointestinal ulcers

• Gastrointestinal bleeding

• Hypertension

This is not a complete list of side effects, but just some of the most common. Please see the Mefenamic acid information leaflet for more detailed information.

Drug Interactions

Mefenamic acid can interact with many other medications when they are used in together, including:

• ACE Inhibitors

• Aldosterone antagonists

• Alendronate

• Amiloride

• Aspirin

• Beta blockers

• Brimonidine

• Calcineurin inhibitors

• Corticosteroids

• Cyclosporin

• Fluconazole

• Lithium

• Loop diuretics

• Methotrexate

• Phenindione

• Potassium

• Prostaglandin analogues

• Rifampicin

• Sartans

• Tacrolimus

• Thiazide diuretics

• Thiazolidinediones

• Triamterene

• Warfarin

These medications can often be used together, but your doctor should be aware that you are taking both medications so that they can adjust the dose as needed to ensure they are safe and effective.

Cautions

There are some people who may need to avoid using Mefenamic acid, or use it with caution, because they may be at risk of side effects due to the medication.

Peptic ulcers or GI bleeding:

Mefenamic acid is not usually used for people who have a history of gastrointestinal bleeding or peptic ulcers. This is because it can increase the risk of peptic ulcers or gastrointestinal bleeding. If it is required, a medication to help prevent gastrointestinal problems, such as esomeprazole or pantoprazole, is usually recommended as well.

Proctitis:

The suppository form of mefenamic acid should not be used if you have proctitis as it can aggravate the condition.

Coagulation disorders:

Mefenamic acid may increase the risk of bleeding or thrombosis because the antiplatelet effect of the prostaglandins may be reduced.

Cardiovascular disease:

Mefenamic acid may cause retention of sodium and fluid in the body, which can make hypertension and heart failure worse. It should not be used if you have heart failure, angina, peripheral artery disease or cerebrovascular disease.

Asthma:

Mefenamic acid may increase the risk of bronchospasm and cause symptoms of asthma to worsen. Some people with asthma can use them without any problems, but it is best to use a low dose and watch for signs of worsening asthma if you are using it for the first time.

Inflammatory Bowel Disease (IBD):

Mefenamic acid may cause symptoms of inflammatory bowel disease to get worse.

Renal Impairment

Mefenamic acid can cause renal impairment is some people, particularly when used in combination with some other medications. If you already have some renal impairment, an NSAID may not be the best choice for you.

Pregnancy and Breastfeeding

Mefenamic acid is not usually recommended for women who are pregnant or trying to conceive. This is because it can interfere with fertility and the development of the fetus.

For women planning to become pregnant, it can prevent or delay ovulation, so that the woman is less likely to conceive. Additionally, using mefenamic acid during pregnancy, particularly at the time of conception, is linked to a higher risk of miscarriage. It may also cause other problems later on in the pregnancy and should be avoided.

For women who are breastfeeding, mefenamic acid is considered safe to use.

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