Mefenamic acid
PONSTEL
Pronunciation: me-fe-NAM-ik AS-id (PON-stel)
“Mef’s Pony’s tail”
“The N said... NSAID”
What it isFenamate NSAID; dysmenorrhea and mild to moderate pain.
Why this oneParticularly effective for dysmenorrhea, where it reduces menstrual blood loss as well as pain.
What limits itDiarrhea is prominent among the fenamates, and overdose causes seizures. Standard NSAID GI and renal risk; it raises serum lithium.
FDA-approved for
- pain/dysmenorrhea (~1967)
FDA label
Read the full label on DailyMed ↗
| FDA dosing | Population | Start | Target | Max |
|---|---|---|---|---|
| Mild to moderate pain | Adults & ≥14 yr | 500 mg once, then 250 mg q6h PRN | 250 mg q6h PRN | |
| Primary dysmenorrhea | Adults & ≥14 yr | 500 mg once, then 250 mg q6h (from onset of bleeding) | 250 mg q6h |
Renal Should not be given to patients with pre-existing renal disease or significantly impaired renal function; avoid in advanced renal disease unless benefits outweigh risks.
Hepatic May require reduced doses in acute or chronic hepatic disease.
Instructions
- Use the lowest effective dose for the shortest duration.
- Avoid using more than one NSAID at a time.
Available strengths
- cap 250 mg
Contraindications
- History of asthma, urticaria, or other allergic-type reactions to aspirin or other NSAIDs.
- In the setting of coronary artery bypass graft (CABG) surgery.
Cautions
- Cardiovascular thrombotic events (MI, stroke).
- GI bleeding, ulceration, perforation.
- Hepatotoxicity.
- Hypertension; heart failure and edema.
- Renal toxicity and hyperkalemia.
- Anaphylactic reactions; aspirin-sensitive asthma (contraindicated).
- Serious skin reactions (SJS, TEN, DRESS).
- Fetal toxicity; hematologic toxicity.
Adverse reactions
- abdominal pain, constipation, diarrhea, dyspepsia, flatulence, heartburn, nausea, vomiting
- GI ulcers/gross bleeding/perforation
- dizziness, headache
- pruritus, rashes
- tinnitus
- edema, anemia
- elevated liver enzymes, abnormal renal function, increased bleeding time
Pregnancy Avoid at ~30 weeks gestation and later (premature closure of fetal ductus arteriosus); limit dose/duration at 20–30 weeks (oligohydramnios/fetal renal dysfunction).
Lactation Present in human milk in low amounts; weigh benefits against potential effects on the infant.
Cost
| Strength | #/mo | generic $/unit | CostPlus | |
|---|---|---|---|---|
| 250 mg | cap | per unit | $0.95/ea | offered |
Generic entry2010
⚠ BOXED WARNINGS
- Cardiovascular thrombotic events
- Gastrointestinal bleeding, ulceration and perforation
Classes and tags
Clinical profile
Legacy pregnancy categoryMultiple / indication-, trimester- or formulation-dependent
Defining liabilityGI bleeding, kidney injury, hypertension and fluid retention; many agents increase lithium concentrations.
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