What is Mefenamic Acid used for?

Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) predominantly used to treat mild to moderate pain, including menstrual pain, and sometimes arthritis. It is marketed under various trade names, including Ponstel and Ponstan. Mefenamic acid works by targeting the enzymes responsible for inflammation and pain, specifically cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2). This drug falls under the class of anthranilic acid derivatives (or fenamates) and has been the subject of extensive research since its development in the 1960s by Parke-Davis, now a subsidiary of Pfizer.

Its primary indications include the treatment of dysmenorrhea (painful menstruation) and pain management for conditions such as arthritis and other musculoskeletal disorders. In some cases, mefenamic acid is also prescribed for short-term relief of mild to moderate pain from various sources, such as dental pain or headaches. Research and clinical trials have consistently demonstrated its efficacy in these applications, although newer NSAIDs have somewhat overshadowed its use in recent years due to the development of drugs with more favorable side effect profiles.

Mefenamic acid's mechanism of action revolves around its ability to inhibit the enzymes COX-1 and COX-2, which play a crucial role in the biosynthesis of prostaglandins. Prostaglandins are lipid compounds that mediate inflammation, pain, and fever. By inhibiting these enzymes, mefenamic acid effectively reduces the production of prostaglandins, alleviating pain and inflammation.

COX-1 is involved in maintaining the normal lining of the stomach, protecting the gastrointestinal tract, and supporting platelet function. COX-2, on the other hand, is primarily active at sites of inflammation. While inhibition of COX-2 is desirable for reducing pain and inflammation, inhibition of COX-1 can lead to gastrointestinal side effects, which is a common challenge with NSAIDs, including mefenamic acid.

Mefenamic acid is typically administered orally, in the form of capsules or tablets. The usual dose for adults and children over 14 years of age is 500 mg initially, followed by 250 mg every 6 hours as needed, for no more than seven days. For the treatment of primary dysmenorrhea, the medication should be started with the onset of menstruation and continued for 2-3 days. It is essential to follow the prescribed dosage and not to exceed the recommended duration of use, as prolonged consumption can increase the risk of side effects.

The onset of action for mefenamic acid is relatively quick, with pain relief usually occurring within 1-2 hours after ingestion. For optimal results, it should be taken with food or milk to minimize gastrointestinal discomfort. Patients are advised to drink a full glass of water with each dose and avoid lying down for at least 10 minutes after taking the medication.

Like all medications, mefenamic acid can cause side effects. Common side effects include gastrointestinal issues such as nausea, vomiting, diarrhea, constipation, and abdominal pain. These are often manageable and can be mitigated by taking the medication with food. More serious gastrointestinal side effects can include ulcers, bleeding, and perforation, which require immediate medical attention.

Other potential side effects include dizziness, headache, and drowsiness. In rare cases, mefenamic acid can cause severe allergic reactions, manifesting as rash, itching, swelling, severe dizziness, or difficulty breathing. If any of these symptoms occur, it is crucial to seek medical help promptly.

Mefenamic acid is contraindicated in certain populations. Patients with a history of hypersensitivity to mefenamic acid or any other NSAIDs should avoid this medication. It is also contraindicated in individuals with active gastrointestinal bleeding or ulcer disease, as well as those with severe renal impairment. Pregnant women, especially in the third trimester, should not use mefenamic acid due to potential risks to the fetus, including premature closure of the ductus arteriosus. Breastfeeding mothers are also advised to avoid this medication, as it can pass into breast milk and potentially harm the nursing infant.

Several other drugs can interact with mefenamic acid, potentially altering its effectiveness or increasing the risk of adverse effects. For example, anticoagulants such as warfarin can increase the risk of bleeding when taken with mefenamic acid. Similarly, other NSAIDs or corticosteroids can exacerbate gastrointestinal side effects, and combining these medications should be done with caution.

Diuretics and antihypertensive drugs, including ACE inhibitors and angiotensin II receptor blockers, may have their efficacy reduced when taken with mefenamic acid, potentially leading to increased blood pressure or fluid retention. Lithium, used for bipolar disorder, and methotrexate, used for certain cancers and autoimmune diseases, can also interact with mefenamic acid, leading to increased toxicity and requiring careful monitoring.

Additionally, certain antidepressants, such as selective serotonin reuptake inhibitors (SSRIs), can increase the risk of bleeding when combined with mefenamic acid. It is essential for patients to inform their healthcare provider of all medications they are taking, including over-the-counter drugs and supplements, to avoid potential interactions.

In conclusion, mefenamic acid is a valuable NSAID for the treatment of mild to moderate pain, particularly menstrual pain. Its mechanism of action involves inhibiting the COX enzymes, thereby reducing prostaglandin production and alleviating pain and inflammation. While effective, it is crucial to be aware of its potential side effects and contraindications, as well as possible drug interactions, to ensure safe and effective use. Always consult with a healthcare provider before starting or combining mefenamic acid with other medications.