Mefenamic acid Side Effects

Medically reviewed by Drugs.com. Last updated on Jun 12, 2023.

Applies to mefenamic acid: oral capsule.

Warning

Oral route (Capsule)

NSAIDs cause an increased risk of serious cardiovascular thrombotic events, including myocardial infarction and stroke, which can be fatal. This risk may occur early in treatment and may increase with duration of use. Mefenamic acid is contraindicated in the setting of CABG surgery. NSAIDs can also cause an increased risk of serious gastrointestinal (GI) adverse events including bleeding, ulceration, and perforation of the stomach or intestines, which can be fatal. These events can occur at any time during use and without warning symptoms. Elderly patients and patients with a prior history of peptic ulcer disease or GI bleeding are at greater risk for serious GI events.

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:

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 rash
loss of appetite
lower back or side pain
nausea
pale skin
severe stomach pain, cramping, or burning
stomach bloating
swelling of the face, fingers, feet, or lower legs
trouble breathing
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 or tightness
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
fainting
fast, pounding, or irregular heartbeat or pulse
fever or chills
frequent urge to urinate
headache
increased volume of pale, dilute urine
irregular, rapid, or slow 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
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
tremors
unpleasant breath odor
upper right stomach pain
yellow eyes and skin

Rare

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
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

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:

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

Rare

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.

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]

General

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]

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

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]

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]