Mefenamic acid 500mg tablets or capsules are

a prescription non-steroidal anti-inflammatory drug (NSAID) primarily used for the short-term relief of mild to moderate pain and menstrual pain. 

Key Information

• Drug Class: Mefenamic acid belongs to the anthranilic acid derivatives (fenamate) class of non-steroidal anti-inflammatory drugs (NSAIDs).

• Mechanism of Action: It works by blocking the body's production of prostaglandins, natural chemicals that cause pain, fever, and inflammation. It may also compete for binding at the prostaglandin receptor sites.

• Indications:

• Relief of mild to moderate acute pain (generally for no longer than one week).

• Treatment of primary dysmenorrhea (period pain).

• Treatment of heavy periods (menorrhagia) due to dysfunctional causes.

• Relief of pain associated with conditions such as rheumatoid arthritis, osteoarthritis, muscle/joint injuries, and dental pain.

• Dosage: The typical adult dose is one 500mg tablet or capsule taken three times a day, usually with food to help reduce stomach upset. The initial dose is often 500mg, followed by 250mg every 6 hours as needed.

• Physical Appearance: 500mg tablets or capsules are typically yellow, oval-shaped, film-coated tablets or opaque capsules, though appearance can vary by manufacturer (e.g., brand name Ponstan capsules are aqua blue and ivory). 

Important Safety Information

Mefenamic acid is a prescription-only medication and should be used under a doctor's supervision due to potential serious side effects. 

• Serious Risks: The medication carries a risk of serious cardiovascular events (heart attack, stroke), gastrointestinal bleeding or ulcers, and kidney damage, which may be fatal. The risk is generally higher with long-term use, higher doses, and in patients with pre-existing conditions.

• Contraindications: Do not take mefenamic acid if you have a history of allergic reactions to NSAIDs (including aspirin), a current stomach ulcer or gastrointestinal bleeding, severe heart/liver/kidney problems, or are in the third trimester of pregnancy.

• Common Side Effects: Common side effects can include diarrhea, nausea, stomach pain, gas, constipation, headache, and dizziness.

• Interactions: Inform your doctor about all other medications you are taking, especially blood thinners (like warfarin), steroids, or other NSAIDs, as mefenamic acid can interact with them and increase the risk of adverse effects. 

Always read the patient information leaflet provided with the medication for full details and consult a healthcare professional for any questions.