Mefenamic Acid

Trade Names:
Ponstel
- Capsules 250 mg

Pharmacology

Decreases inflammation, pain, and fever, probably through inhibition of cyclooxygenase activity and prostaglandin synthesis.

Indications and Usage

Relief of moderate pain lasting less than 1 wk; treatment of primary dysmenorrhea.

Unlabeled Uses

Treatment of sunburn, migraine (acute attack), PMS.

Contraindications

Patients in whom aspirin, iodides, or any NSAID has caused allergic-type reactions; preexisting renal disease; active ulceration or chronic inflammation of GI tract.

Dosage and Administration

PO 500 mg, followed by 250 mg every 6 h as needed. Usually not used more than 1 wk.

PO 500 mg, followed by 250 mg every 6 h starting with onset of bleeding and associated symptoms.

Storage/Stability

Store at room temperature (59° to 86°F) in tightly closed, light-resistant container.

Drug Interactions

Increased risk of gastric erosion and bleeding.

Nephrotoxicity of both agents may be increased.

Exercise caution when coadministering mefenamic acid with drugs known to inhibit the isoenzyme 2C9.

Serum lithium levels may be increased.

Increased methotrexate levels.

Additive GI toxicity.

Laboratory Test Interactions

May cause prolonged bleeding time or false-positive reaction for urinary bile using diazo tablet test.

Adverse Reactions

Cardiovascular

Edema; weight gain; CHF; altered BP; palpitations; chest pain; bradycardia; tachycardia.

CNS

Headache; vertigo; drowsiness; dizziness; insomnia.

Dermatologic

Rash; urticaria; purpura.

EENT

Blurred vision; tinnitus; salivation; glossitis.

GI

Diarrhea; dry mouth; vomiting; abdominal pain; dyspepsia; GI bleeding; nausea; constipation; flatulence.

Genitourinary

Hematuria; proteinuria; dysuria; renal failure.

Hematologic

Decreased hematocrit; bleeding; neutropenia; leukopenia; pancytopenia; eosinophilia; thrombocytopenia.

Hepatic

Mild elevations in LFT results.

Respiratory

Bronchospasm; laryngeal edema; rhinitis; dyspnea; pharyngitis; hemoptysis; shortness of breath.

Miscellaneous

Autoimmune hemolytic anemia may occur if used long term.

Precautions

Pregnancy

Category C .

Lactation

Undetermined.

Children

Not recommended for children younger than 14 yr of age.

Elderly

Increased risk of adverse reactions.

Hypersensitivity

May occur; use with caution in aspirin-sensitive individuals because of possible cross sensitivity.

Renal Function

Acute renal insufficiency, interstitial nephritis, hyperkalemia, hyponatremia, and renal papillary necrosis may occur. Lower doses may be necessary in patients with renal function impairment.

Diarrhea

If diarrhea occurs, reduce dosage or temporarily discontinue.

GI toxicity

Bleeding, ulceration, or perforation can occur at any time, with or without warning symptoms.

Rash

Promptly discontinue if rash develops.

Overdosage

Symptoms

Acute renal failure, coma, grand mal seizures, muscle twitching, status epilepticus.

Patient Information

• Inform patient not to use drug for longer than 1 wk. If given for dysmenorrhea, instruct patient to begin taking drug with onset of bleeding and associated symptoms.
• Warn patient about potential for bleeding, and advise patient to notify other health care professionals that drug is being taken.
• Advise patient to discontinue medication if rash develops and to contact health care provider.
• Instruct patient to report the following symptoms to health care provider: rash, visual problems, dark stools, decreased urinary output, persistent headache or stomach pain and unusual bruising or bleeding.
• Advise patient to avoid intake of alcoholic beverages.
• Instruct patient that drug may cause drowsiness and to use caution while driving or performing other activities requiring mental alertness.
• Caution patient to avoid prolonged exposure to sunlight and to use sunscreen or wear protective clothing to avoid photosensitivity reaction.
• Instruct patient not to take OTC medications, including aspirin and ibuprofen or other prescription drugs, without consulting health care provider.

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