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Mefenamic acid Side Effects

For the Consumer

Applies to mefenamic acid: oral capsule

Along with its needed effects, mefenamic acid may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while 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 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 feeling in the throat
  • pinpoint red or purple spots on the skin
  • pounding in the ears
  • rapid, slow breathing
  • redness, swelling, or soreness of the tongue
  • severe or continuing stomach pain
  • 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 stomach pain
  • 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 suddenly getting up from a lying or sitting position
  • 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 or back
  • sweating
  • swollen, painful, or tender lymph glands in the neck, armpit, or groin
  • unexplained weight loss

Get emergency help immediately if any of the following symptoms of overdose occur while taking mefenamic acid:

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

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

More common
  • Continuing ringing or buzzing or other unexplained noise in the ears
  • excess air or gas in the stomach or intestines
  • feeling of fullness
  • 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 the 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
  • trouble concentrating
  • trouble sleeping
  • 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. MHRA. Medicines and Health Regulatory Agency "MHRA Drug Safety Update. Available from: URL:"

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

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

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

Some side effects of mefenamic acid may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.

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.