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Mefenamic acid Side Effects

In Summary

More frequently reported side effects include: abdominal pain, diarrhea, and nausea. See below for a comprehensive list of adverse effects.

For the Consumer

Applies to mefenamic acid: oral capsule

In addition to its needed effects, some unwanted effects may be caused by mefenamic acid. In the event that any of these side effects do occur, they may require medical attention.

Major Side Effects

You should check with your doctor immediately if any of these side effects occur when taking mefenamic acid:

More common:
  • Bloody urine
  • bloody, black, or tarry stools
  • decreased frequency or amount of urine
  • heartburn
  • increased bleeding time
  • increased blood pressure
  • increased thirst
  • indigestion
  • itching skin
  • loss of appetite
  • lower back or side pain
  • nausea
  • pale skin
  • rashes
  • severe abdominal pain, cramping, or burning
  • stomach bloating
  • swelling
  • swelling of the face, fingers, feet, or lower legs
  • trouble breathing with or without exertion
  • unusual bleeding or bruising
  • unusual tiredness or weakness
  • vomiting
  • vomiting of material that looks like coffee grounds, severe and continuing
  • weight gain
  • weight loss
Less common:
  • Bleeding gums
  • blood in vomit
  • blurred vision
  • burning feeling in the chest or stomach
  • chest pain
  • clay-colored stools
  • cloudy urine
  • confusion
  • constipation
  • cough or hoarseness
  • dark urine
  • difficult or labored breathing
  • difficult, burning, or painful urination
  • difficulty in swallowing
  • dilated neck veins
  • dizziness
  • extreme fatigue
  • fainting
  • fast, pounding, or irregular heartbeat or pulse
  • fever or chills
  • frequent urge to urinate
  • headache
  • increased volume of pale, dilute urine
  • irregular breathing
  • irregular heartbeat
  • large, flat, blue, or purplish patches in the skin
  • light-colored stools
  • lightheadedness
  • nervousness
  • noisy breathing
  • pain or burning throat
  • pinpoint red or purple spots on the skin
  • pounding in the ears
  • rapid, slow breathing
  • redness, swelling, or soreness of tongue
  • severe or continuing stomach pain
  • shortness of breath
  • slow heartbeat
  • sore throat
  • sores, ulcers, or white spots on the lips or tongue or inside the mouth
  • stomach upset
  • swelling or inflammation of the mouth
  • swollen glands
  • tenderness in the stomach area
  • tightness in the chest
  • tremors
  • unpleasant breath odor
  • upper right abdominal pain
  • weight changes
  • wheezing
  • yellow eyes and skin
  • Blistering, peeling, or loosening of the skin
  • change in consciousness
  • chest discomfort
  • continuing vomiting
  • cracks in the skin
  • diarrhea
  • dizziness, faintness, or lightheadedness when getting up from a lying or sitting position suddenly
  • drowsiness
  • fever with or without chills
  • flushed, dry skin
  • fruit-like breath odor
  • general body swelling
  • general feeling of illness
  • high fever
  • hives
  • increased hunger
  • irregular, fast or slow, or shallow breathing
  • joint or muscle pain
  • large, hive-like swelling on the face, eyelids, lips, tongue, throat, hands, legs, feet, or sex organs
  • leg pain
  • loss of consciousness
  • loss of heat from the body
  • no blood pressure
  • no breathing
  • no pulse
  • nosebleeds
  • painful glands
  • pain or discomfort in the arms, jaw, back, or neck
  • pains in the stomach, side, or abdomen, possibly radiating to the back
  • pale or blue lips, fingernails, or skin
  • puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
  • racing heartbeat or pulse
  • red skin lesions, often with a purple center
  • red, irritated eyes
  • red, swollen skin
  • redness or soreness of the skin
  • scaly skin
  • seeing, hearing, or feeling things that are not there
  • seizures
  • severe headache
  • sneezing
  • sores, welting, or blisters
  • stiff neck and/or back
  • sweating
  • swollen, painful, or tender lymph glands in the neck, armpit, or groin
  • unexplained weight loss

If any of the following symptoms of overdose occur while taking mefenamic acid, get emergency help immediately:

Symptoms of overdose:
  • Unusual drowsiness, dullness, tiredness, weakness, or feeling of sluggishness

Minor Side Effects

Some of the side effects that can occur with mefenamic acid may not need medical attention. As your body adjusts to the medicine during treatment these side effects may go away. Your health care professional may also be able to tell you about ways to reduce or prevent some of these side effects. If any of the following side effects continue, are bothersome or if you have any questions about them, check with your health care professional:

More common:
  • Acid or sour stomach
  • belching
  • continuing ringing or buzzing or other unexplained noise in the ears
  • excess air or gas in the stomach or intestines
  • full feeling
  • hearing loss
  • passing gas
  • stomach discomfort
Less common:
  • Burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings
  • discouragement
  • dry mouth
  • fear
  • feeling of constant movement of self or surroundings
  • feeling sad or empty
  • hair loss, thinning of the hair
  • increased sensitivity of skin to sunlight
  • irritability
  • lack of appetite
  • lack of interest or pleasure
  • lack or loss of strength
  • redness or other discoloration of the skin
  • sensation of spinning
  • severe sunburn
  • sleepiness
  • sleeplessness
  • trouble concentrating
  • trouble sleeping
  • unable to sleep
  • Appetite changes
  • burning, dry, or itching eyes
  • change in hearing
  • discharge, excessive tearing
  • redness, pain, swelling of the eye, eyelid, or inner lining of the eyelid

For Healthcare Professionals

Applies to mefenamic acid: oral capsule


Common (1% to 10%): Abdominal pain, constipation, diarrhea, dyspepsia, flatulence, gross bleeding/perforation, heartburn, nausea, gastric ulcers, duodenal ulcers, vomiting
Rare (less than 0.1%): Eructation, pancreatitis
Frequency not reported: Peptic ulcer, dry mouth, esophagitis, gastritis, GI bleeding, glossitis, hematemesis, melena, rectal bleeding, stomatitis, anorexia, colitis, enterocolitis, pyrosis, steatorrhea, GI inflammation, ulcerative stomatitis, exacerbation of Crohn's disease, gastritis[Ref]


The most frequently reported side effects were gastrointestinal (GI) in nature and included abdominal pain, constipation, diarrhea, dyspepsia, flatulence, gross bleeding/perforation, heartburn, nausea, vomiting, and gastric or duodenal ulcers.[Ref]


Rare (less than 0.1%): Hypotension, arrhythmia, myocardial infarction, palpitations, vasculitis
Frequency not reported: Congestive heart failure, tachycardia, hypertension, cardiac failure, arterial thrombotic events[Ref]


Cases of autoimmune hemolytic anemia have been reported with continuous use of this drug for 12 months or longer. In such cases, the Coombs tests were positive for both accelerated RBC production and destruction. The process was reversible upon discontinuation of therapy.[Ref]

Common (1% to 10%): Anemia, bleeding time increased
Rare (less than 0.1%): Agranulocytosis, hemolytic anemia, aplastic anemia, lymphadenopathy, pancytopenia
Frequency not reported: Eosinophilia, leukopenia, thrombocytopenia, bone marrow hypoplasia, hematocrit decreased, thrombocytopenic purpura, disseminated intravascular coagulation, neutropenia, autoimmune hemolytic anemia, eosinophilia, platelet aggregation inhibition[Ref]


Rare (less than 0.1%): Hyperglycemia
Frequency not reported: Hyponatremia, glucose intolerance, anorexia[Ref]

Nervous system

Common (1% to 10%): Dizziness, headache, drowsiness
Rare (less than 0.1%): Convulsions, coma
Frequency not reported: Syncope, paresthesia, somnolence, tremors, optic neuritis[Ref]


Rare (less than 0.1%): Respiratory distress, pneumonia
Frequency not reported: Asthma, dyspnea, bronchospasm, aggravated asthma, laryngeal edema[Ref]


Common (1% to 10%): Rash, pruritus
Rare (less than 0.1%): Angioedema, toxic epidermal necrolysis, Stevens-Johnson syndrome, erythema multiforme, exfoliative dermatitis, urticaria
Frequency not reported: Ecchymosis, purpura, alopecia, photosensitivity, sweating[Ref]


Common (1% to 10%): Elevated liver enzymes
Rare (less than 0.1%): Liver failure
Frequency not reported: Hepatitis, jaundice, cholestatic jaundice, hepatorenal syndrome, mild hepatic toxicity[Ref]


Rare (less than 0.1%): Conjunctivitis
Frequency not reported: Blurred vision, eye irritation, reversible loss of color vision, visual disturbances[Ref]


Frequency not reported: Cystitis, dysuria, hematuria, oliguria, polyuria, proteinuria, false positive urobilinogen urine[Ref]


Common (1% to 10%): Abnormal renal function
Frequency not reported: Interstitial nephritis, renal failure, allergic/non-allergic glomerulonephritis, nephrotic syndrome, non-oliguric renal failure, renal papillary necrosis, tubulointerstitial nephritis[Ref]


Rare (less than 0.1%): Hallucinations
Frequency not reported: Anxiety, confusion, depression, dream abnormalities, insomnia, nervousness[Ref]


Rare (less than 0.1%): Anaphylactoid/anaphylactic reaction
Frequency not reported: Hypersensitivity reaction, non-specific allergic reaction[Ref]


Common (1% to 10%): Edema, tinnitus
Rare (less than 0.1%): Death, meningitis, appetite changes, hearing impairment
Frequency not reported: Fever, infection, sepsis, weight changes, asthenia, malaise, vertigo, aseptic meningitis, ear pain, face edema, fatigue, malaise, multi-organ failure, pyrexia, fluid retention, edema of the larynx[Ref]


1. "Product Information. Ponstel (mefenamic acid)." Pfizer U.S. Pharmaceuticals Group, New York, NY.

2. MHRA. Medicines and Health Regulatory Agency "MHRA Drug Safety Update. Available from: URL:"

3. Cerner Multum, Inc. "Australian Product Information." O 0

4. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0

Not all side effects for mefenamic acid may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This material does not endorse drugs, diagnose patients, or recommend therapy. This information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate safety, effectiveness, or appropriateness for any given patient. does not assume any responsibility for any aspect of healthcare administered with the aid of materials provided. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the substances you are taking, check with your doctor, nurse, or pharmacist.