Pharmacology
Mechanism of action
Like other members of the anthranilic acid derivatives (or fenamate) class of NSAIDs, it inhibits both isoforms of the enzyme cyclooxygenase (COX-1 and COX-2). This prevents formation of prostaglandins, which play a role in pain sensitivity, inflammation and fever, but also in hemostasis, kidney function, sustaining of pregnancy, and protection of the gastric mucosa. Pharmacokinetics
Mefenamic acid is rapidly absorbed from the gut and reaches highest concentrations in the blood plasma after one to four hours. When in the bloodstream, over 90% of the substance are bound to plasma proteins. It probably crosses the placenta, and is found in the breast milk in small amounts.It is metabolized by the liver enzyme CYP2C9 to the only weakly active 3-hydroxymethylmefenamic acid. 3-carboxymefenamic acid has also been identified as a metabolite, as well as carboxy glucuronides of all three substances. Mefenamic acid and its metabolites are excreted via the urine (52–67%) and the faeces (20–25%, or less than 20% following another source). The parent substance has a biological half-life of two hours; the half-life of its metabolites may be longer. History
Scientists led by Claude Winder from Parke-Davis invented mefenamic acid in 1961, along with fellow members of the class of anthranilic acid derivatives, flufenamic acid in 1963 and meclofenamate sodium in 1964.: 718   U.S. Patent 3,138,636 on the drug was issued in 1964.: 918–919 It was approved in the UK in 1963 as Ponstan, in West Germany in 1964 as Ponalar and in France as Ponstyl, and the US in 1967 as Ponstel.
Mefenamic acid is a member of the anthranilic acid derivatives (or fenamate) class of nonsteroidal anti-inflammatory drugs (NSAIDs), and is used to treat mild to moderate pain.Its name derives from its systematic name, dimethylphenylaminobenzoic acid. It was discovered and brought to market by Parke-Davis in the 1960s. It became generic in the 1980s and is available worldwide under many brand names such as Meftal. Medical uses
Mefenamic acid is used to treat pain and inflammation in rheumatoid arthritis and osteoarthritis, postoperative pain, acute pain including muscle and back pain, toothache and menstrual pain, as well as being prescribed for menorrhagia.There is evidence that supports the use of mefenamic acid for perimenstrual migraine headache prophylaxis, with treatment starting two days prior to the onset of flow or one day prior to the expected onset of the headache and continuing for the duration of menstruation.Mefenamic acid is recommended to be taken with food. Contraindications
Mefenamic acid is contraindicated in people who have shown hypersensitivity reactions such as urticaria and asthma to this drug or to other NSAIDs (e.g. aspirin); those with peptic ulcers or chronic inflammation of the gastrointestinal tract; those with kidney or liver disease; heart failure; after coronary artery bypass surgery; and during the third trimester of pregnancy. Side effects
Known mild side effects of mefenamic acid include headaches, nervousness, and vomiting. Potentially serious side effects may include diarrhea, gastrointestinal perforation, peptic ulcers, hematemesis (vomiting blood), skin reactions (rashes, itching, swelling; in rare cases toxic epidermal necrolysis) and rarely blood cell disorders such as agranulocytosis.