mefenamic acid at a glance
Medicine class
A fenamate non-steroidal anti-inflammatory drug (NSAID).
Main roles
Relieves inflammatory and other pain, including painful periods; selected solid formulations are also licensed for defined causes of heavy periods.
Administration
Taken by mouth. Tablets and capsules are preferably taken with or after food; capsules should be swallowed with water.
Important stop signal
Stop taking it and contact a clinician if diarrhoea develops.
What is mefenamic acid used for?
Licensed indications vary by formulation and include:
Symptomatic relief of rheumatoid arthritis, including Still’s disease, and osteoarthritis.
Muscular, traumatic, dental, postoperative and postpartum pain, and headaches of most causes.
Primary dysmenorrhoea (painful periods).
Menorrhagia caused by dysfunctional bleeding or an intrauterine device, after other pelvic disease has been excluded; this applies to selected solid formulations.
The selected suspension is also licensed for fever in children and primary dysmenorrhoea in older children.
How does mefenamic acid work?
Mefenamic acid inhibits cyclo-oxygenase activity, reducing prostaglandin production. Prostaglandins contribute to inflammation, pain, fever, uterine cramping and menstrual blood loss.
mefenamic acid preparations and strengths
Capsule
Route: Oral
Strengths: 250 mg
Oral suspension
Route: Oral
Strengths: 50 mg/5 mL
Tablet
Route: Oral
Strengths: 500 mg
How to take mefenamic acid
Take mefenamic acid exactly as directed on the dispensing label. It is taken by mouth; tablets and capsules are preferably taken with or after food.
Swallow capsules with a drink of water.
Avoid heavy alcohol consumption because it can increase stomach irritation and gastrointestinal bleeding risk.
Do not take it with another NSAID, such as ibuprofen, naproxen or diclofenac, unless specifically directed by a clinician.
If dizziness, drowsiness or visual disturbance occurs, do not drive or operate machinery.
mefenamic acid side effects
Common or expected effects
- Gastrointestinal effects, including nausea, vomiting, indigestion, abdominal pain, wind and constipation.
- Diarrhoea: stop treatment and contact a clinician.
- Dizziness, drowsiness, tiredness, headache, ringing in the ears and skin rash.
Get urgent medical advice
- Stomach or intestinal ulceration, bleeding or perforation, which may present with severe pain, vomiting blood or black stools.
- Severe allergic reactions, bronchospasm or worsening asthma.
- Serious blistering or peeling skin reactions.
- Kidney injury, liver injury, blood-cell disorders, severe fluid retention, heart failure, heart attack or stroke.
- Seizures, particularly following overdose.
mefenamic acid in pregnancy
Mefenamic acid is not advised during pregnancy unless prescribed after clinical assessment. NSAIDs should generally be avoided from week 20 because exposure can affect fetal kidney function, amniotic-fluid volume and the ductus arteriosus; mefenamic acid is contraindicated during the third trimester. Contact a doctor or midwife promptly if it has been taken after week 20 without supervision, particularly on several occasions.
mefenamic acid interactions
Check prescribed, pharmacy and non-prescription medicines before use. Important interactions include:
Other NSAIDs, including ibuprofen, naproxen, diclofenac, aspirin used for pain, and COX-2 inhibitors
Combining NSAIDs increases gastrointestinal, kidney and other adverse-effect risks and should be avoided unless directly supervised.
Warfarin, heparin and other anticoagulants
Can increase anticoagulant effects and bleeding risk; specialist supervision and coagulation monitoring may be required.
Common questions about mefenamic acid
Answers are fully visible for fast scanning and source review.
What is mefenamic acid used for?
It is licensed for inflammatory arthritis, several types of pain and painful periods. Selected solid formulations are also licensed for defined causes of heavy menstrual bleeding.
Should mefenamic acid be taken with food?
Selected tablets and capsules are preferably taken with or after food; capsules should also be swallowed with water.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.