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mefenamic acid (Rx)Brand and Other Names:

 
 
 

Dosing & Uses

AdultPediatricGeriatric

Dosage Forms & Strengths

capsule

  • 250mg
more...

Acute Pain

Initial 500 mg PO once, THEN

250 mg PO q6hr PRN usually not to exceed 7 days

Primary Dysmenorrhea

Initial 500 mg PO once, THEN

250 mg PO q6hr PRN usually not to exceed 3 days

Administration

Take with food or 8-12 oz water to avoid GI effects

For dysmenorrhea, start with onset of bleeding & pain

Other Indications & Uses

Off-label: Vascular headache

Dosage Forms & Strengths

capsule

  • 250mg
more...

Acute Pain

<14 years old: Not recommended

≥14 years old: Initial 500 mg PO once, THEN

250 mg PO q6hr PRN usually not to exceed 7 days

Primary Dysmenorrhea

<14 years old: Not recommended

≥14 years old: Initial 500 mg PO once, THEN

250 mg PO q6hr PRN usually not to exceed 3 days

Acute pain

Initial 500 mg PO once, THEN

250 mg PO q6hr PRN usually not to exceed 7 days

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Interactions

Interaction Checker

mefenamic acid and

No Results

     
     activity indicator 
    No Interactions Found
    Interactions Found

    Contraindicated

      Serious - Use Alternative

        Significant - Monitor Closely

          Minor

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            Adverse Effects

            >10%

            Borderline elevations of one or more LFTs (<15%)

            1-10%

            Abdominal pain

            Anorexia

            Diarrhea

            Nausea

            Pyrosis

            Gastritis

            Flatulence

            Constipation

            Steatorrhea

            Upper GI ulcers, gross bleeding/perforation (1% of patients treated for 3-6 mth and 2-4% of those treated for 1 yo)

            <1%

            Leukopenia

            Eosinophilia

            Thrombocytopenic purpura

            Agranulocytosis

            Pancytopenia

            Bone marrow hypoplasia

            Renal failure (including papillary necrosis & acute interstitial nephritis)

            Acute interstitial nephritis has been associated with hematuria, proteinuria, & nephrotic syndrome

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            Warnings

            Black Box Warnings

            Cardiovascular risk

            • NSAIDs may increase risk of serious cardiovascular thrombotic events, myocardial infarction (MI), & stroke, which can be fatal
            • Risk may increase with duration of use
            • Patients with risk factors for or existing cardiovascular disease may be at greater risk
            • NSAIDs are contraindicated for perioperative pain in the setting of coronary artery bypass graft (CABG) surgery (increased risk of MI & stroke)

            Gastrointestinal risk

            • NSAIDs increase risk of serious GI adverse events including bleeding, ulceration, & perforation of the stomach or intestines, which can be fatal
            • GI adverse events may occur at any time during use & without warning symptoms
            • Elderly patients are at greater risk for serious GI events

            Contraindications

            Hypersensitivity, ASA allergy, history of aspirin triad, GI tract ulcer/inflammation, CABG, renal dz, late pregnancy (may cause premature closure of ductus arteriosus)

            Cautions

            Anemia, bronchospasm, cardiac dz, CHF, HTN, SLE, fluid retention, hepatic/renal impairment, bleeding diathesis

            Long-term administration of NSAIDs may result in renal papillary necrosis and other renal injury; patients at greatest risk include the elderly, or those with impaired renal function, hypovolemia, heart failure, liver dysfunction, salt depletion, and individuals taking diuretics, ACE inhibitors, or ARBs

            History of: peptic ulcer, GI bleeding, upper GI disease

            If severe diarrhea occurs, reduce dose or temporarily discontinue drug

            Risk of serious skin reactions

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            Pregnancy & Lactation

            Pregnancy Category: C; D if used for prolonged periods, or near term (premature closure of ductus arteriosus)

            The Quebec Pregnancy Registry identified 4705 women who had spontaneous abortions by 20 weeks' gestation; each case was matched to 10 control subjects (n=47,050) who had not had spontaneous abortions; exposure to nonaspirin NSAIDs during pregnancy was documented in approximately 7.5% of cases of spontaneous abortions and in approximately 2.6% of controls. (CMAJ, September 6, 2011; DOI:10.1503/cmaj.110454)

            Lactation: contraindicated; excreted in breast milk

            Pregnancy Categories

            A:Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

            B:May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.

            C:Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.

            D:Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.

            X:Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.

            NA:Information not available.

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            Pharmacology

            Mechanism of Action

            Inhibits synthesis of prostaglandins in body tissues by inhibiting at least 2 cyclooxygenase isoenzymes, cyclooxygenase-1 (COX-1) and -2 (COX-2)

            May inhibit chemotaxis, may alter lymphocyte activity, decrease proinflammatory cytokine activity, and may inhibit neutrophil aggregation.  These effects may contribute to its anti-inflammatory activity

            Pharmacokinetics

            Half-life: 2 hr

            Onset: Rapid

            Peak Plasma Time: 2-4 hr (1 g dose); reached by the second day of administration (1 g dose, 4x daily)

            Peak Plasma Concentration: 10 mcg/mL (1 g dose); 20 mcg/mL (1 g dose, 4x daily)

            Protein Bound: Extensive

            Metabolism: Hepatic oxidation/conjugation

            Metabolites: 3'-hydroxymethyl and 3'-carboxyl acid metabolites and their glucuronic acid conjugates

            Enzymes inhibited: Cyclooxygenase

            Excretion: urine 66% (single dose); feces 20-25%

            Dialyzable: No

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            Images

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            Formulary

            FormularyPatient Discounts

            To view formulary information first create a list of plans. Your list will be saved and can be edited at any time.

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            • View the formulary and any restrictions for each plan.
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            • Compare formulary status to other drugs in the same class.
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            The above information is provided for general informational and educational purposes only. Individual plans may vary and formulary information changes. Contact the applicable plan provider for the most current information.

            Tier Description
            1 This drug is available at the lowest co-pay. Most commonly, these are generic drugs.
            2 This drug is available at a middle level co-pay. Most commonly, these are "preferred" (on formulary) brand drugs.
            3 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs.
            4 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            5 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            6 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            NC NOT COVERED – Drugs that are not covered by the plan.
            Code Definition
            PA Prior Authorization
            Drugs that require prior authorization. This restriction requires that specific clinical criteria be met prior to the approval of the prescription.
            QL Quantity Limits
            Drugs that have quantity limits associated with each prescription. This restriction typically limits the quantity of the drug that will be covered.
            ST Step Therapy
            Drugs that have step therapy associated with each prescription. This restriction typically requires that certain criteria be met prior to approval for the prescription.
            OR Other Restrictions
            Drugs that have restrictions other than prior authorization, quantity limits, and step therapy associated with each prescription.
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