Mefenamic acid is a non‑steroidal anti‑inflammatory drug (NSAID) used mainly for pain, fever and dysmenorrhea (painful menstruation). Because it can affect the stomach, kidneys, liver, and clotting system, it’s important to follow the instructions below and to check with a healthcare provider before you start.
1. Typical Adult Dosing
| Condition |
Typical Dose |
Frequency |
Total Daily Dose |
Duration |
| Pain or Fever |
250 mg to 500 mg |
Every 6–8 hours |
1 – 2 g |
As needed, up to 3–4 days (never exceed 3 g/day) |
| Dysmenorrhea (painful periods) |
250 mg |
Twice daily (12 h apart) |
500 mg/day |
3–5 days, usually beginning 12–24 h before menses and continuing until pain resolves |
| Rheumatoid Arthritis |
250 mg |
Every 6–8 hours |
1 – 2 g |
Long‑term; only under a doctor’s supervision |
Never take more than the maximum recommended dose (≈3 g/day) and limit use to the shortest effective period.
2. How to Take It
| Step |
Detail |
| Take with Food or Milk |
Helps reduce stomach irritation and nausea. |
| Drink Plenty of Water |
At least 8‑12 oz after each dose to aid absorption and reduce GI irritation. |
| Avoid Alcohol |
Alcohol increases the risk of stomach bleeding and kidney problems. |
| Do Not Crush or Chew (unless instructed) |
The tablet is designed to release slowly; crushing can cause GI upset. |
| Follow the Schedule |
Keep the interval between doses as close to the prescribed timing (e.g., 6–8 hours) as possible. |
| Keep a Pill Organizer |
Helps avoid accidental double‑dosing. |
3. When to Call Your Doctor
- Severe stomach pain, vomiting, or black/tarry stools (possible GI bleeding)
- Swelling or pain in the legs (possible kidney or heart issues)
- Unusual bruising or bleeding (bleeding disorders)
- High fever, persistent nausea, or dizziness
- Pregnancy or breastfeeding (NSAIDs are generally avoided)
If you are pregnant, planning to become pregnant, or nursing, consult your provider before using mefenamic acid.
4. Drug Interactions
| Drug |
Potential Interaction |
Why It Matters |
| Other NSAIDs (ibuprofen, naproxen, aspirin) |
Increased GI and renal toxicity |
Avoid overlapping doses |
| Anticoagulants (warfarin, rivaroxaban) |
Elevated bleeding risk |
Monitor INR/bleeding signs |
| ACE inhibitors / ARBs |
Reduced antihypertensive effect & increased kidney risk |
Monitor blood pressure & kidney function |
| Diuretics |
Additive risk of kidney injury |
Monitor kidney function |
| SSRIs / SNRIs |
Increased bleeding risk |
Watch for bleeding |
| Methotrexate |
Increased toxicity |
Use only under supervision |
Always tell your pharmacist or doctor about all medications and supplements you’re taking.
5. Precautions & Contraindications
- History of ulcers or GI bleeding → higher risk of further bleeding.
- Kidney or liver disease → dose reduction or avoidance.
- Heart disease → increased risk of cardiovascular events.
- Peptic ulcer disease → contraindicated.
- Pregnancy (especially 3rd trimester) → avoid.
- Lactation → avoid; not recommended.
If you have any of these conditions, discuss alternatives with your provider.
6. Common Side Effects
| Symptom |
What to Do |
| Stomach upset, heartburn, nausea |
Take with food; if persistent, stop and consult a clinician. |
| Headache, dizziness |
Rest; monitor for worsening. |
| Rash or itching |
Stop use and seek medical advice if severe. |
| Swelling of hands/legs |
Stop use; see a doctor (possible kidney or heart issue). |
| Dark urine or reduced urine output |
Stop use and seek medical attention immediately. |
7. Summary
- Take mefenamic acid with food or milk, at least 8 oz of water, and avoid alcohol.
- Stick to the prescribed dose and interval (e.g., 250–500 mg every 6–8 hours, not exceeding 3 g/day).
- Watch for GI upset, bleeding, or kidney problems and contact a provider if symptoms arise.
- Never use it while pregnant, breastfeeding, or without a doctor’s guidance if you have heart, kidney, or liver disease.
- Discuss all other medications to avoid interactions.
Important: This information is meant for general guidance only. For personalized advice, dosage adjustments, or to discuss whether mefenamic acid is suitable for you, consult your prescribing doctor or pharmacist.