Mefenamic acid and Contraindications

Mefenamic acid is a member of the anthranilic acid derivative (or anthranilate) class of nonsteroidal anti-inflammatory drugs (NSAIDs) used to treat mild to moderate pain.Its name is derived from its systematic name, dimethylphenylaminobenzoic acid. In the 1960s, Parke-Davis discovered and marketed it under the Ponstel name.It became generic in the 1980s and is sold worldwide under many brand names such as Meftal.

Medical use 

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, and for the treatment of menorrhagia.Evidence supports the use of mefenamic acid to prevent menstrual migraine, starting two days before blood flow begins or the day before expected headache onset and continuing until menstruation.Mefenamic acid is recommended to be taken with food.

Contraindications

Mefenamic acid is contraindicated in persons who have exhibited hypersensitivity reactions to this drug or other NSAIDs such as aspirin, such as urticaria and asthma; persons with peptic ulcers or chronic inflammation of the gastrointestinal tract; People with kidney or liver disease; heart failure; after coronary artery bypass surgery; during the third trimester of pregnancy.

Side effects

Known mild side effects of mefenamic acid include headache, nervousness, and vomiting.Potentially serious side effects may include diarrhea, gastrointestinal perforation, peptic ulcer, hematemesis (spitting blood), skin reactions (rash, itching, swelling; in rare cases toxic epidermal necrolysis) and rare blood cell disorders such as agranulocytosis.It is associated with acute liver injury.In 2008, US labels were updated to warn about the risk of premature closure of the ductus arteriosus during pregnancy.In October 2020, the U.S. Food and Drug Administration (FDA) required updates to drug labels on all NSAIDs to describe the risk of kidney problems in an unborn baby resulting in low amniotic fluid.They advise pregnant women at 20 weeks or later to avoid NSAIDs.

Overdose

Symptoms of overdose include kidney failure, gastrointestinal problems, bleeding, rash, confusion, hallucinations, dizziness, seizures, and loss of consciousness.It is treated by emetic induction, gastric lavage, bone char, control of electrolytes and vital functions.

Interactive

Interactions are broadly similar to those of other NSAIDs.Mefenamic acid interferes with the anticoagulant mechanism of aspirin.It increases the blood-thinning effects of warfarin and phenprocoumon by displacing their binding to plasma proteins and increasing their free concentrations in the bloodstream.It increases the risk of gastrointestinal ulcers associated with corticosteroids and selective serotonin reuptake inhibitors.It may increase the risk of adverse effects of methotrexate and lithium by decreasing renal excretion.Can increase the nephrotoxicity of cyclosporine and tacrolimus.Concomitant use with antihypertensive drugs such as ACE inhibitors, sartans, and diuretics reduces their effectiveness and increases the risk of nephrotoxicity.