Mefenamic Acid Side Effects

Medically reviewed by Drugs.com. Last updated on Aug 15, 2024.

Applies to mefenamic acid: oral capsule.

Precautions

It is very important that your doctor check your progress at regular visits. to make sure this medicine is working properly. Blood and urine tests may be needed to check for unwanted effects.

This medicine may raise your risk of having a heart attack or stroke. This is more likely in people who already have heart disease or in people who use this medicine for a long time. Check with your doctor right away if you are having chest pain or discomfort, nausea or vomiting, pain or discomfort in the arms, jaw, back, or neck, trouble breathing, slurred speech, or weakness.

This medicine may cause bleeding in your stomach or intestines. These problems can happen without warning signs. This is more likely if you have had a stomach ulcer in the past, if you smoke or drink alcohol regularly, are over 60 years of age, are in poor health, or using certain other medicines (eg, steroid medicine, blood thinner).

Check with your doctor right away if you have pain or tenderness in the upper stomach, pale stools, dark urine, loss of appetite, nausea, vomiting, or yellow eyes or skin. These could be symptoms of a serious liver problem.

Serious skin reactions, including exfoliative dermatitis, Stevens-Johnson syndrome, toxic epidermal necrolysis, and drug reaction with eosinophilia and systemic symptoms (DRESS) can occur with this medicine. Check with your doctor right away if you have black, tarry stools, blistering, peeling, or loosening of the skin, chest pain, chills, cough, diarrhea, fever, itching, joint or muscle pain, painful or difficult urination, red irritated eyes, red skin lesions, sore throat, sores, ulcers, or white spots in the mouth or on the lips, swollen glands, unusual bleeding or bruising, or unusual tiredness or weakness.

Some possible warning signs of some serious side effects that can occur during treatment with this medicine may include swelling of the face, fingers, feet, or lower legs, severe stomach pain, black, tarry stools, or vomiting of blood or material that looks like coffee grounds, unusual weight gain, yellow skin or eyes, decreased urination, bleeding or bruising, or skin rash. Also, signs of serious heart problems could occur including chest pain or tightness, fast or irregular heartbeat, unusual flushing or warmth of skin, weakness, or slurring of speech. Check with your doctor immediately if you notice any of these warning signs.

Check with your doctor right away if you have bloody urine, a decrease in frequency or amount of urine, an increase in blood pressure, increased thirst, loss of appetite, lower back or side pain, nausea, swelling of the face, fingers, or lower legs, trouble breathing, unusual tiredness or weakness, vomiting, or weight gain. These could be symptoms of a serious kidney problem.

Hyperkalemia (high potassium in the blood) may occur while you are using this medicine. Check with your doctor right away if you have stomach pain, confusion, difficulty with breathing, irregular heartbeat, nausea or vomiting, nervousness, numbness or tingling in the hands, feet, or lips, or weakness or heaviness of the legs.

This medicine may cause a serious allergic reaction called anaphylaxis, which can be life-threatening and requires immediate medical attention. Tell your doctor right away if you have a rash, itching, hoarseness, trouble breathing, trouble swallowing, or any swelling of your hands, face, or mouth after using this medicine.

This medicine may cause a delay in ovulation for women and may affect their ability to have children. If you plan to have children, talk with your doctor before using this medicine.

Using this medicine during the later part of a pregnancy can harm your unborn baby. If you think you have become pregnant while using this medicine, tell your doctor right away.

Make sure any doctor or dentist who treats you knows that you are using this medicine. This medicine may affect the results of certain medical tests.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

Serious side effects of mefenamic acid

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:

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

Other side effects of mefenamic acid

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:

For healthcare professionals

Applies to mefenamic acid: oral capsule.

General adverse events

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]

Gastrointestinal

• 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]

Cardiovascular

• 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]

Hematologic

• 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]

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]

Metabolic

• 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]

Respiratory

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

Dermatologic

• 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]

Hepatic

• 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]

Ocular

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

Genitourinary

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

Renal

• 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]

Psychiatric

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

Hypersensitivity

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

Other

• 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]

See also:

Further information

Mefenamic acid side effects can vary depending on the individual. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Note: Medication side effects may be underreported. If you are experiencing side effects that are not listed, submit a report to the FDA by following this guide.

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