What it is used for
- Period pain (painful menstruation)
- Heavy menstrual bleeding
- Mild to moderate pain such as headache, dental and muscle pain
- Inflammation
How it works
Mefenamic acid blocks the COX enzymes that make prostaglandins, reducing pain and inflammation. By lowering prostaglandins in the womb, it is particularly useful for period pain and heavy periods.
How it is taken
Available as capsules, tablets and oral suspension. Take it exactly as your doctor, pharmacist or the label directs, usually with or after food. It is often used for short courses around menstruation.
No doses here on purpose. The right strength and schedule depend on you — only a doctor or pharmacist should set them. Always follow your prescription and the label.
Common side effects
- Indigestion or stomach discomfort
- Diarrhoea
- Nausea
- Headache or drowsiness
Serious effects — get help
- Stomach or gut bleeding or ulcers (black stools, vomiting blood, severe abdominal pain)
- Serious allergic reaction or asthma flare
- Severe diarrhoea, sometimes with rash (a reason to stop and seek advice)
- Heart attack or stroke warning signs
- Signs of kidney problems; in overdose, seizures can occur
If a reaction is severe — for example trouble breathing, swelling of the face or throat, or collapse — go to the nearest emergency room now or call your local emergency number. Do not wait for an online consultation.
Interactions to watch
- Other NSAIDs and aspirin
- Blood thinners and antiplatelet drugs
- Some blood pressure medicines and diuretics
- Lithium and methotrexate
- Corticosteroids and SSRIs (bleeding risk)
- Alcohol
Who should take care
- Avoided in late pregnancy; use only on clinician advice otherwise
- Stop and seek advice if diarrhoea or a rash develops, as this can signal a reaction
- Tell your doctor about ulcers, asthma, inflammatory bowel disease, heart disease, or kidney or liver problems
- Use the lowest effective amount for the shortest time
- Seek urgent care for gut bleeding, severe reaction or seizures