Mefenamic Acid
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) used for short-term mild to moderate pain and for painful periods (primary dysmenorrhea).
🧬 Where this information comes from Click to expand
The clinical label records used on this page are FDA-filed Structured Product Labeling (SPL) retrieved through openFDA. We identified 6 clinical label sets within the page’s selected clinical scope after exact ingredient or ingredient-combination matching and applicable route/form matching. Forms, routes, brands, labelers, strengths, and NDC product-record counts are built separately from matching FDA National Drug Code Directory records. The linked DailyMed document is a representative official source for verification, not the page’s only clinical source. View the linked label on DailyMed →
Mefenamic acid (Ponstel) is an older NSAID (anti-inflammatory pain reliever) that blocks the COX-1 and COX-2 enzymes driving pain and inflammation, prescribed for a week or less of mild to moderate pain and for painful periods; on the market since about 1984 and available as a generic, it is used less often than ibuprofen or naproxen. Most people tolerate a short course well, with stomach upset, heartburn and diarrhea the usual complaints. The boxed warning covers heart attack, stroke and stomach or intestinal bleeding that can be fatal, so take the lowest dose for the shortest time and get help for chest pain or black or bloody stools.
Clinical pearls
- Do not take it past seven days for pain; for period cramps, start when bleeding and symptoms begin.
- Skip antacids containing magnesium hydroxide, such as milk of magnesia, because they increase how much mefenamic acid your body absorbs.
- Avoid other NSAIDs like ibuprofen or naproxen with it, and never use it as a stand-in for heart-protective low-dose aspirin.
- It is not for people with kidney disease; tell your prescriber first about heart or liver disease or past stomach ulcers.
⚠️ FDA Boxed Warning — the FDA’s strongest safety alert ▾
Mefenamic acid can raise your risk of heart attack, stroke, and serious stomach or intestinal bleeding, which can be fatal.
The heart risk can start early in treatment and may grow the longer you take it. It should never be used around CABG heart surgery.
Stomach or intestinal bleeding, ulcers and perforation can happen at any time, often with no warning symptoms. Older adults and people who have had stomach ulcers or GI bleeding are at higher risk.
Patient information guide A plain-language walkthrough of Mefenamic Acid, written from its FDA label.
What Mefenamic Acid is used for
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Mefenamic acid is an NSAID used for short-term pain and menstrual cramps.
- Mild to moderate pain in adults and teens 14 and older, for no more than 7 days (mefenamic acid capsules).
- Primary dysmenorrhea, meaning painful periods with no other underlying cause (mefenamic acid capsules).
How Mefenamic Acid works
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Mefenamic acid blocks COX-1 and COX-2 enzymes. These enzymes make prostaglandins, which make nerves more sensitive to pain and drive inflammation. Lowering prostaglandins can reduce pain and inflammation. The exact mechanism is not completely understood.
Mefenamic Acid dosage
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Mefenamic acid capsules are taken by mouth. Typically you start with a larger first dose, then take a smaller dose about every 6 hours. For pain it is taken as needed. For painful periods it is started when bleeding and symptoms begin.
- Your prescriber should use the lowest effective dose for the shortest time.
- Your prescriber may adjust the dose and timing based on how you respond.
- Follow your prescription label for exact directions.
Dosing details from the FDA-approved label
From the Mefenamic Acid prescribing information (“Dosage and Administration”). Doses are set by your prescriber for your product, condition, kidney function and age — never change a dose on your own.
- Management of mild to moderate pain (adults and pediatric patients 14 years of age and older)
- 500 mg given orally as an initial dose followed by 250 mg every 6 hours as needed
- Use the lowest effective dose for the shortest duration; adjust dose and frequency to the individual patient's needs after observing response
- Dysmenorrhea (primary dysmenorrhea)
- 500 mg given orally as an initial dose followed by 250 mg every 6 hours starting with the onset of bleeding and associated symptoms
- Use the lowest effective dose for the shortest duration
Read the label’s full dosing text
2 DOSAGE AND ADMINISTRATION Adults and adolescents 14 years of age and older: 500 mg given orally as an initial dose followed by 250 mg every 6 hours as needed ( 2.2 ) For the treatment of primary dysmenorrhea: 500 mg given orally as an initial dose followed by 250 mg every 6 hours ( 2.3 ) 2.1 Important Dosage and Administration Information Carefully consider the potential benefits and risks of mefenamic acid capsules and other treatment options before deciding to use mefenamic acid capsules. Use the lowest effective dose for the shortest duration consistent with individual patient treatment goals [see Warnings and Precautions ( 5.2 )] . After observing the response to initial therapy with mefenamic acid capsules, the dose and frequency should be adjusted to suit an individual patient's needs. 2.2 For the Management of Mild to Moderate Pain The recommended dosage in adults and pediatric patients 14 years of age and older is 500 mg given orally as an initial dose followed by 250 mg every 6 hours as needed. 2.3 Dysmenorrhea The recommended dose is 500 mg given orally as an initial dose followed by 250 mg every 6 hours starting with the onset of bleeding and associated symptoms.
Read the full Dosage and Administration section on DailyMed →
Mefenamic Acid side effects
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The most common side effects are mostly stomach-related:
Common side effects
- Stomach pain
- Nausea or vomiting
- Diarrhea or constipation
- Indigestion, heartburn or gas
- Dizziness
- Headache
- Rash or itching
- Ringing in the ears (tinnitus)
- Swelling, anemia or abnormal kidney or liver tests
When to get medical help
- Get emergency help for chest pain, shortness of breath, weakness on one side of the body, or slurred speech. These can be signs of a heart attack or stroke.
- Call your doctor right away if you have black or bloody stools, vomit blood, or have severe stomach pain. These can be signs of stomach or intestinal bleeding, ulcers or perforation.
- Stop the medicine and get help at the first sign of a skin rash, blisters, fever, swollen glands or facial swelling. These can be serious skin or allergic reactions, including DRESS.
- Seek emergency help for signs of a severe allergic reaction, such as trouble breathing or swelling.
- Call your doctor if you have nausea, unusual tiredness, itching, yellow skin or eyes, right upper belly tenderness, or flu-like symptoms. These can be signs of liver problems.
- Tell your doctor about swelling, fluid retention, new or worsening high blood pressure, or signs of anemia.
Get medical help right away for black or bloody stools, vomiting blood, chest pain, trouble breathing, skin blistering, severe rash, yellow skin or eyes, or swelling of the face.
Mefenamic Acid warnings and precautions
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- Heart attack and stroke: risk can start early and rises with longer use. Never use around CABG surgery.
- Stomach bleeding, ulcers and perforation: can happen without warning and can be fatal. Risk is higher in older adults, people with past ulcers or bleeding, and those who smoke, drink alcohol, or take steroids, blood thinners, aspirin or SSRIs.
- Liver: rare but severe injury has been reported.
- Blood pressure, heart failure and fluid retention: NSAIDs can cause or worsen these.
- Kidneys: long-term use can cause kidney injury, and potassium levels can rise.
- Skin and allergic reactions: including Stevens-Johnson syndrome, toxic epidermal necrolysis and DRESS. Stop at the first rash.
- Anemia and asthma: anemia can occur, and people with asthma should be watched for changes.
- Pregnancy: avoid at about 30 weeks or later.
Mefenamic Acid interactions
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Mefenamic acid can interact with several common medicines:
- Warfarin and other blood thinners: much higher bleeding risk.
- Aspirin and other NSAIDs or salicylates: more stomach toxicity without extra benefit.
- SSRIs and SNRIs: may increase bleeding risk.
- ACE inhibitors, ARBs, beta-blockers and diuretics: NSAIDs can weaken their effect and strain the kidneys.
- Digoxin, lithium, methotrexate, cyclosporine, pemetrexed: levels or toxicity may increase.
- Magnesium hydroxide antacids: increase mefenamic acid absorption.
- It may prolong prothrombin time and cause a false-positive urine bile test.
Interactions listed in the FDA-approved label
From the Mefenamic Acid prescribing information (“Drug Interactions”): what the manufacturer studied or reported to the FDA.
- Anticoagulants (e.g., warfarin), antiplatelet agents (e.g., aspirin), SSRIs, and SNRIs (drugs that interfere with hemostasis): Mefenamic acid and anticoagulants such as warfarin have a synergistic effect on bleeding, with increased risk of serious bleeding compared to either drug alone; SSRIs/SNRIs with an NSAID may potentiate bleeding risk more than an NSAID alone. Monitor patients for signs of bleeding.
- Aspirin: Concomitant NSAID and analgesic doses of aspirin produces no greater therapeutic effect than the NSAID alone and was associated with a significantly increased incidence of GI adverse reactions. Concomitant use with analgesic doses of aspirin is not generally recommended because of the increased risk of bleeding; mefenamic acid is not a substitute for low dose aspirin for cardiovascular protection.
- ACE inhibitors, angiotensin receptor blockers, and beta-blockers: NSAIDs may diminish the antihypertensive effect of these drugs; in elderly, volume-depleted or renally impaired patients, co-administration with ACE inhibitors or ARBs may result in deterioration of renal function, including possible acute renal failure. Monitor blood pressure; in elderly, volume-depleted or renally impaired patients monitor for worsening renal function; ensure adequate hydration and assess renal function at the beginning of concomitant treatment and periodically thereafter.
- Diuretics (loop diuretics e.g., furosemide, and thiazide diuretics): NSAIDs reduced the natriuretic effect of loop and thiazide diuretics in some patients. Observe patients for signs of worsening renal function and for diuretic efficacy including antihypertensive effects.
- Digoxin: Concomitant use has been reported to increase the serum concentration and prolong the half-life of digoxin. Monitor serum digoxin levels.
- Lithium: NSAIDs have produced elevations in plasma lithium levels and reductions in renal lithium clearance. Monitor patients for signs of lithium toxicity.
- Methotrexate: Concomitant use of NSAIDs and methotrexate may increase the risk for methotrexate toxicity (e.g., neutropenia, thrombocytopenia, renal dysfunction). Monitor patients for methotrexate toxicity.
- Cyclosporine: Concomitant use may increase cyclosporine's nephrotoxicity. Monitor patients for signs of worsening renal function.
- Other NSAIDs or salicylates (e.g., diflunisal, salsalate): Concomitant use increases the risk of GI toxicity, with little or no increase in efficacy. Concomitant use is not recommended.
- Pemetrexed: Concomitant use may increase the risk of pemetrexed-associated myelosuppression, renal, and GI toxicity. In patients with creatinine clearance 45 to 79 mL/min, monitor for myelosuppression, renal and GI toxicity. NSAIDs with short half-lives (e.g., diclofenac, indomethacin) should be avoided for two days before, the day of, and two days following pemetrexed; for NSAIDs with longer half-lives (e.g., meloxicam, nabumetone), interrupt dosing for at least five days
Read the label’s full interactions text
7 DRUG INTERACTIONS 7.1 Drug Interactions See Table 1 for clinically significant drug interactions with mefenamic acid. Table1: Clinically Significant Drug Interactions with Mefenamic Acid Drugs That Interfere with Hemostasis Clinical Impact: Mefenamic acid and anticoagulants such as warfarin have a synergistic effect on bleeding. The concomitant use of mefenamic acid and anticoagulants have an increased risk of serious bleeding compared to the use of either drug alone. Serotonin release by platelets plays an important role in hemostasis. Case-control and cohort epidemiological studies showed that concomitant use of drugs that interfere with serotonin reuptake and an NSAID may potentiate the risk of bleeding more than an NSAID alone. Intervention: Monitor patients with concomitant use of mefenamic acid with anticoagulants (e.g., warfarin), antiplatelet agents (e.g., aspirin), selective serotonin reuptake inhibitors (SSRIs), and serotonin norepinephrine reuptake inhibitors (SNRIs) for signs of bleeding [see Warnings and Precautions ( 5.12 )] . Aspirin Clinical Impact: Controlled clinical studies showed that the concomitant use of NSAIDs and analgesic doses of aspirin does not produce any greater therapeutic effect than the use of NSAIDs alone. In a clinical study, the concomitant use of an NSAID and aspirin was associated with a significantly increased incidence of GI adverse reactions as compared to use of the NSAID alone [see Warnings and Precautions ( 5.2 )] . Intervention: Concomitant use of mefenamic acid and analgesic doses of aspirin is not generally recommended because of the increased risk of bleeding [see Warnings and Precautions ( 5.12 )] . Mefenamic acid is not a substitute for low dose aspirin for cardiovascular protection.
Excerpted — the section continues on the label. Read the full Drug Interactions section on DailyMed →
Not a complete list. The label covers the interactions the manufacturer studied or reported, and our own interaction database does not cover every medicine either. Bring your full medication list, including vitamins and herbal products, to your pharmacist.
Before taking Mefenamic Acid
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- Do not use if allergic to mefenamic acid, or if aspirin or NSAIDs have caused asthma, hives or allergic reactions.
- Do not use around CABG surgery.
- Use caution with recent heart attack, heart failure, high blood pressure, or past stomach ulcers or bleeding.
- Should not be given with existing kidney disease or significantly impaired kidney function.
- Liver disease may require a lower dose.
- Pregnancy: avoid at about 30 weeks or later; limit use between about 20 and 30 weeks.
- Breastfeeding: it is present in milk in low amounts.
- May reversibly affect fertility.
- Not established for pain under age 14.
- Older adults have higher risks and need careful dosing.
Mefenamic Acid overdose
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Too much can cause lethargy, drowsiness, nausea, vomiting and upper stomach pain. Stomach bleeding can occur, and high blood pressure, acute kidney failure, slowed breathing and coma are rare. There is no specific antidote, so care is supportive. Contact a poison control center at 1-800-222-1222.
What Mefenamic Acid does in the body
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Mefenamic acid has pain-relieving, anti-inflammatory and fever-reducing activity. Like other NSAIDs, it is thought to work through blocking prostaglandin production.
How your body processes Mefenamic Acid
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Mefenamic acid is rapidly absorbed by mouth, with peak levels in about 2 to 4 hours. Its half-life is about 2 hours. It is broken down in the liver by the CYP2C9 enzyme and cleared mostly through the urine, with some in stool. Kidney or liver disease may allow its breakdown products to build up. Magnesium hydroxide antacids increase its absorption.
How to store Mefenamic Acid
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Store at 25°C (77°F); excursions permitted to 15° to 30°C (59° to 86°F) .
Written from the FDA-approved label with AI and reviewed by our pharmacy team. How we use AI →
Supplements & herbs that interact with Mefenamic Acid
118 supplements and herbal products have documented interactions with Mefenamic Acid in the licensed clinical database we use. Most are manageable — but your pharmacist should know about everything you take, including vitamins and herbals.
- Major · 5
- Moderate · 86
- Minor · 27
Educational information from a licensed clinical database (Natural Medicines) — see our data sources & update cadence. Not medical advice: an interaction being documented does not mean it will happen to you; do not start or stop medications or supplements without professional guidance.
Nutrient depletion considerations
Mefenamic Acid has been associated with lower levels of 1 nutrient in the clinical literature. This does not mean a deficiency will occur — it means these may be worth discussing with your pharmacist or healthcare provider, especially with long-term use.
Educational information from a licensed clinical database (Natural Medicines) — not medical advice. Do not start or stop medications or supplements without professional guidance.
Mefenamic Acid: pharmacist answers to common questions
Quick, plain-English answers to the questions patients ask most about Mefenamic Acid — the kind of thing our pharmacy team would talk through with you at the counter.
What is mefenamic acid for?
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How should I take it?
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What side effects should I expect?
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When should I get help right away?
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Can I take it with aspirin or other pain relievers?
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Is it safe in pregnancy?
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Is Mefenamic Acid available over the counter?
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When was Mefenamic Acid first available?
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Who makes Mefenamic Acid?
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Answers drafted from the FDA-approved label with AI and reviewed by our pharmacy team. How we use AI →
More about Mefenamic Acid on HelloPharmacist
Mefenamic Acid forms and strengths (how it comes)
Mefenamic Acid is available in 1 form. Different forms and brands can have different approved uses, doses, schedules, and directions. Follow the instructions for your exact product, and do not switch forms without guidance from your prescriber or pharmacist.
Capsule
How this form is used
- Mefenamic acid capsules are used for mild to moderate pain in people 14 and older, for no more than 7 days.
- Mefenamic acid capsules are used to treat primary dysmenorrhea.
- Mefenamic acid capsules are taken by mouth, with a larger first dose followed by smaller doses about every 6 hours.
- For pain, mefenamic acid capsules are taken as needed.
- For painful periods, mefenamic acid capsules are started at the onset of bleeding and symptoms.
Mefenamic Acid on the U.S. market: products, makers and brands
How Mefenamic Acid appears in the FDA’s National Drug Code Directory — including its dosage forms, strengths, brand names, manufacturers, and FDA-listed product records. These are directory records, not sales or prescription volume.
6 companies list 6 Mefenamic Acid product records with the FDA, mostly as capsule; the earliest marketing or approval year on record is 1967. Brand names on the directory include Ponstel; the rest are generics.
Also listed with the FDA, not a patient dose form: Powder (6) — bulk drug substance sold to compounders/manufacturers and multi-item kits. These aren’t counted in the dose-form total above.
Share of FDA-listed product records by manufacturer — FDA National Drug Code Directory. Record counts are not sales or prescription volume.
How widely Mefenamic Acid is used (Medicaid data)
A general measure of how commonly Mefenamic Acid is prescribed, based on Medicaid — one of the largest public drug programs. The figure below is prescriptions filled in Q1–Q4 2025, summed across every form and brand of the drug.
Think of this as a proxy for how widely Mefenamic Acid is used, drawn from freely available public data. Medicaid is just one program — these numbers don’t include Medicare, other government coverage, or commercial and cash-pay prescriptions, so real-world use is higher than what’s shown here.
How commonly is Mefenamic Acid prescribed? Of the 1,601 medications we measure, Mefenamic Acid ranks #1,201 by Medicaid prescriptions — more than 25% of them.
Utilization by Mefenamic Acid product
Pick a product to see its own Medicaid numbers. Each chip is one clinical product — a specific strength & dosage form as defined by RxNorm — with brand-name and generic versions combined.
Other Mefenamic Acid products — combination packs and listings not yet matched to a specific clinical product (kept visible so every prescription is accounted for)
Summed across the 2 of 28 listed NDC products with Medicaid activity.
Shares are of the Medicaid prescriptions shown here. Product grouping follows RxNorm (the National Library of Medicine’s drug terminology), so “one product” means one strength & dosage form regardless of manufacturer. Dollar figures are gross Medicaid reimbursement before mandatory rebates — rebates (often large, especially for brand-name drugs) are confidential, so actual net cost to Medicaid is lower than shown.
Source: Medicaid State Drug Utilization Data (CMS), aggregated by generic ingredient — summed across every NDC (all brands, strengths, salt forms and dosage forms) of Mefenamic Acid, and across all states and both fee-for-service and managed-care claims. A general popularity signal; it excludes Medicare, commercial insurance and cash prescriptions, so it is not total U.S. use. Based on the 2 of 28 listed Mefenamic Acid NDCs with Medicaid activity.
Compare Mefenamic Acid products
A representative set of FDA-listed product records for Mefenamic Acid — across manufacturers, strengths, and dosage forms, grouped by form with each product’s manufacturer and how the FDA approved it. The same medicine may be made and packaged by different companies, so a single drug can have many directory entries. (It’s also why a refill can look different — a new shape, color, or box — even though it contains the same medication.)
| Strength | Route | Manufacturer / Labeler | Category ⓘ | Details |
|---|---|---|---|---|
| 💊Capsule | ||||
| 250 mg | Oral | Advanced Rx of Tennessee, LLC | ANDA | View NDC → |
| 250 mg | Oral | Advanced Rx Pharmacy of Tennessee, LLC | ANDA | View NDC → |
| 250 mg | Oral | Bryant Ranch Prepack | ANDA | View NDC → |
| 250 mg | Oral | Lupin Pharmaceuticals, Inc. | ANDA | View NDC → |
| 250 mg | Oral | Micro Labs Limited | ANDA | View NDC → |
| 250 mg | Oral | Misemer Pharmaceuticals, Inc | ANDA | View NDC → |
Showing 6 of 6 products — FDA National Drug Code Directory. See every product, package size and price: browse all 6 Mefenamic Acid NDCs →
Mefenamic Acid side effects reported to the FDA (FAERS)
After a medicine reaches the market, patients, doctors and drugmakers can send the FDA reports of problems they think may be linked to it. Here’s what’s been reported for Mefenamic Acid — a signal of what to watch for, not proof the drug caused it.
Source: openFDA, from the FDA Adverse Event Reporting System (FAERS). These are voluntary reports — they don’t prove the drug caused the effect, and counts reflect how often something was reported, not how often it actually happens. Reports also often name the very problem the medicine is taken for — a common reason to file one is that the drug didn’t help — so for a pain reliever you may see “pain” high on the list; that points to why the report was filed, not to the drug causing the symptom. This counts every report that lists Mefenamic Acid in any role, so the total runs higher than the FDA’s official dashboard, which counts only cases where the drug is the suspect. For the authoritative figures, see the FDA FAERS Public Dashboard. Always talk to your pharmacist or doctor.
Mefenamic Acid FDA approval history
How Mefenamic Acid went from FDA review to the pharmacy shelf — the key milestones in its regulatory journey.
Source: Drugs@FDA.
Mefenamic Acid recall history
A recall is when a specific batch of a medicine is pulled from the market — usually a manufacturing issue, not a problem with the drug itself. Class I is most serious, Class III least.
The FDA’s enforcement reports list no Mefenamic Acid recalls since July 2021.
✅No Mefenamic Acid recalls on record since July 2021Source: FDA enforcement (recall) reports, via openFDA; our copy was last updated Sep 24, 2026.
Mefenamic Acid supply and shortage status
Whether Mefenamic Acid is in short supply in the U.S. right now, plus any shortage history the FDA has on record. A shortage usually reflects a manufacturing or demand issue — not a safety problem with the drug.
Source: openFDA, from the FDA Drug Shortages database.
Mefenamic Acid brand names
Mefenamic Acid is sold under one brand name in the FDA directory — Ponstel. A brand and its generic contain the same active ingredient; the brand name belongs to one company's product.
Who makes Mefenamic Acid: manufacturers and labelers
6 companies list Mefenamic Acid products with the FDA. By number of product records, the largest are Advanced Rx Pharmacy of Tennessee, LLC, Advanced Rx of Tennessee, LLC, Bryant Ranch Prepack. Labelers include manufacturers and repackagers; the product in your bottle depends on which one your pharmacy stocks.
Mefenamic Acid drug class (RxNorm)
Mefenamic Acid belongs to the Nonsteroidal Anti-inflammatory Drug class.
Classified by RxNorm RxClass — the U.S. National Library of Medicine's standardized drug-classification service (Established Pharmacologic Class from the FDA, the ATC drug family from the WHO, and mechanism of action). Reference only, not medical advice.
Sources for this Mefenamic Acid page
Core label, product, RxNorm, safety, and utilization data on this page come from the sources identified below. AI-written, editorial, and licensed sections are labeled separately.
How this page is built
HelloPharmacist combines public FDA and NLM records and does not author the underlying clinical facts. The plain-language sections are written with AI from the FDA-approved label text and reviewed by our pharmacy team before publication. Lupin Pharmaceuticals, Inc. is the representative DailyMed label linked for verification and dates. This is general education, not medical advice: always talk to your doctor or pharmacist about your own medicines. How we build and review drug pages →