Mefenamic Acid

Class: Other Nonsteroidal Anti-inflammatory Agents
VA Class: MS120
Chemical Name: N-(2,3-xylyl)anthranilic acid
Molecular Formula: C₁₅H₁₅NO₂
CAS Number: 61-68-7
Brands: Ponstel

• Cardiovascular Risk


• 
  

  Possible increased risk of serious (sometimes fatal) cardiovascular thrombotic events (e.g., MI, stroke).^{125 b} Risk may increase with duration of use.^{125 b} Individuals with cardiovascular disease or risk factors for cardiovascular disease may be at increased risk.^{125 b} (See Cardiovascular Effects under Cautions.)

  
  


• 
  

  Contraindicated for the treatment of pain in the setting of CABG surgery.^{125 b}

  
  

• GI Risk


• 
  

  Increased risk of serious (sometimes fatal) GI events (e.g., bleeding, ulceration, perforation of the stomach or intestine).^{100 104 125 b} Serious GI events can occur at any time and may not be preceded by warning signs and symptoms.^{100 101 104 125 b} Geriatric individuals are at greater risk for serious GI events.^{125 b} (See GI Effects under Cautions.)

  
  

Introduction

Prototypical NSAIA; anthranilic acid derivative (fenamate); structurally and pharmacologically related to meclofenamate sodium.^{125 a}

Uses for Mefenamic Acid

Consider potential benefits and risks of mefenamic acid therapy as well as alternative therapies before initiating therapy with the drug.^{125 b} Use lowest possible effective dosage and shortest duration of therapy consistent with patient’s treatment goals.^{125 b}

Pain

Relief of mild to moderate pain in patients ≥14 years of age when the duration of therapy ≤1 week.^{125 b}

Dysmenorrhea

Treatment of primary dysmenorrhea.^{125 b}

Fever

Has been used for reduction of fever† associated with infection in children; routine use as an antipyretic not recommended because of potential adverse effects.^a

Mefenamic Acid Dosage and Administration

General

• 
  

  Consider potential benefits and risks of mefenamic acid therapy as well as alternative therapies before initiating therapy with the drug.^{125 b}

  
  

Administration

Oral Administration

Administer orally.¹²⁵ May be administered in divided doses up to 4 times daily.¹²⁵

Dosage

To minimize the potential risk of adverse cardiovascular and/or GI events, use lowest effective dosage and shortest duration of therapy consistent with the patient’s treatment goals.^{125 b} Adjust dosage based on individual requirements and response; attempt to titrate to the lowest effective dosage.^{125 b}

Pediatric Patients

Pain

Oral

Adolescents ≥14 years of age should receive dosage recommended for adults.¹²⁵ (See Adult Dosage.)

Adults

Pain

Oral

For mild to moderate pain in adults, 500 mg initially followed by 250 mg every 6 hours as necessary.¹²⁵

Dysmenorrhea

Oral

For relief of primary dysmenorrhea in adults, 500 mg initially followed by 250 mg every 6 hours as necessary.¹²⁵ Initiate at onset of bleeding and associated symptoms; treatment should not be necessary for >2–3 days.¹²⁵

Prescribing Limits

Pediatric Patients

Pain

Oral

Duration of therapy usually should not exceed 1 week.¹²⁵

Adults

Pain

Oral

Duration of therapy usually should not exceed 1 week.¹²⁵

Dysmenorrhea

Oral

Therapy should not be necessary for more than 2–3 days.¹²⁵

Special Populations

Hepatic Impairment

Dosage reduction may be required.¹²⁵

Renal Impairment

Dosage reduction may be required if used in patients with renal impairment.¹²⁵

Use not recommended in patients with preexisting renal disease or substantial renal impairment.¹²⁵

Geriatric Patients

Select dosage carefully since may be more likely to have decreased renal function.^{125 b}

Cautions for Mefenamic Acid

Contraindications

• 
  

  Known hypersensitivity to mefenamic acid or any ingredient in the formulation.^{125 b}

  
  


• 
  

  History of asthma, urticaria, or other sensitivity reaction precipitated by aspirin or other NSAIAs.^{125 b}

  
  


• 
  

  Treatment of perioperative pain in the setting of CABG surgery.^{125 b}

  
  


• 
  

  Active ulceration or chronic inflammation of upper or lower GI tract.¹²⁵

  
  


• 
  

  Preexisting renal disease.¹²⁵

  
  

Warnings/Precautions

Warnings

Cardiovascular Effects

Selective COX-2 inhibitors have been associated with increased risk of cardiovascular events (e.g., MI, stroke) in certain situations.^{125 129} Several prototypical NSAIAs also have been associated with increased risk of cardiovascular events.^{125 133 134 135} Information not available on risk associated with mefenamic acid at this time.^{133 134 135 136}

Use NSAIAs with caution and careful monitoring (e.g., monitor for development of cardiovascular events) and at the lowest effective dosage for the shortest duration necessary.^{125 b}

Short-term use to relieve acute pain, especially at low dosages, does not appear to be associated with increased risk of serious cardiovascular events (except immediately following CABG surgery).^{125 b}

No consistent evidence that concomitant use of low-dose aspirin mitigates the increased risk of serious adverse cardiovascular events associated with NSAIAs.^{125 b} (See Specific Drugs under Interactions.)

Hypertension and worsening of preexisting hypertension reported; either event may contribute to the increased incidence of cardiovascular events.^{125 b} Use with caution in patients with hypertension; monitor BP.^{125 b} Impaired response to certain diuretics may occur.^{125 b} (See Specific Drugs under Interactions.)

Fluid retention and edema reported.^{125 b} Caution in patients with fluid retention or heart failure.^{125 b}

GI Effects

Serious GI toxicity (e.g., bleeding, ulceration, perforation) can occur with or without warning symptoms; increased risk in those with a history of GI bleeding or ulceration, geriatric patients, smokers, those with alcohol dependence, and those in poor general health.^{100 104 124 125 126 b}

For patients at high risk for complications from NSAIA-induced GI ulceration (e.g., bleeding, perforation), consider concomitant use of misoprostol;^{124 127 h i} alternatively, consider concomitant use of a proton-pump inhibitor (e.g., omeprazole)^{124 h i} or use of an NSAIA that is a selective inhibitor of COX-2 (e.g., celecoxib).^{125 h}

Renal Effects

Direct renal injury, including renal papillary necrosis, reported in patients receiving long-term NSAIA therapy.^{125 b}

Potential for overt renal decompensation.^{125 b} Increased risk of renal toxicity in patients with renal or hepatic impairment or heart failure, in geriatric patients, in patients with volume depletion, and in those receiving a diuretic, ACE inhibitor, or angiotensin II receptor antagonist.^{125 128 b} (See Renal Impairment under Cautions.)

Sensitivity Reactions

Hypersensitivity Reactions

Anaphylactoid reactions reported.^{125 b}

Immediate medical intervention and discontinuance for anaphylaxis.^{125 b}

Avoid in patients with aspirin triad (aspirin sensitivity, asthma, nasal polyps); caution in patients with asthma.^{125 b}

Dermatologic Reactions

Serious skin reactions (e.g., exfoliative dermatitis, Stevens-Johnson syndrome, toxic epidermal necrolysis) reported; can occur without warning.^{125 b} Discontinue at first appearance of rash or any other signs of hypersensitivity (e.g., blisters, fever, pruritus).^{125 b}

General Precautions

Hepatic Effects

Severe reactions including jaundice, fatal fulminant hepatitis, liver necrosis, and hepatic failure (sometimes fatal) reported rarely with NSAIAs.^{125 b}

Elevations of serum ALT or AST reported.^{125 b}

Monitor for symptoms and/or signs suggesting liver dysfunction; monitor abnormal liver function test results.^{125 b} Discontinue if signs or symptoms of liver disease or systemic manifestations (e.g., eosinophilia, rash) occur.^{125 b}

Hematologic Effects

Anemia reported rarely.^{125 b} Determine hemoglobin concentration or hematocrit in patients receiving long-term therapy if signs or symptoms of anemia occur.^{125 b}

May inhibit platelet aggregation and prolong bleeding time.^{125 b}

Ocular Effects

Visual disturbances reported; ophthalmic evaluation recommended if visual changes occur.^{125 a}

Other Precautions

Not a substitute for corticosteroid therapy; not effective in the management of adrenal insufficiency.^{125 b}

May mask certain signs of infection.^{125 b}

Obtain CBC and chemistry profile periodically during long-term use.^{125 b}

Specific Populations

Pregnancy

Category C.^{125 b} Avoid use in third trimester because of possible premature closure of the ductus arteriosus.^{125 b}

Lactation

Distributed into milk.^{125 c} Discontinue nursing or the drug.¹²⁵

Pediatric Use

Safety and efficacy not established in children <14 years of age.¹²⁵

Geriatric Use

Use with caution in patients ≥65 years of age.^{125 b} Geriatric adults appear to tolerate therapy less well (e.g., possible higher incidence of adverse GI effects, greater risk of developing renal decompensation) than younger individuals.^{125 b} Fatal adverse GI effects reported more frequently in geriatric patients than younger adults.^{125 b}

Substantially eliminated by kidneys; periodic monitoring of renal function may be useful since geriatric patients are more likely to have decreased renal function.¹²⁵ (See Geriatric Patients under Dosage and Administration and Renal Impairment under Cautions.)

Renal Impairment

Use not recommended in patients with preexisting renal disease or substantial renal impairment.¹²⁵

Common Adverse Effects

Abdominal pain,¹²⁵ constipation,¹²⁵ diarrhea,¹²⁵ dyspepsia,¹²⁵ flatulence,¹²⁵ gross bleeding/perforation,¹²⁵ heartburn,¹²⁵ nausea,¹²⁵ GI ulcers (gastric/duodenal),¹²⁵ vomiting,¹²⁵ abnormal renal function,¹²⁵ anemia,¹²⁵ dizziness,¹²⁵ edema,¹²⁵ elevated liver enzymes,¹²⁵ headaches,¹²⁵ increased bleeding time,¹²⁵ pruritus,¹²⁵ rashes,¹²⁵ tinnitus.¹²⁵

Interactions for Mefenamic Acid

Protein-bound Drugs

Possible pharmacokinetic interaction; potential for mefenamic acid to be displaced from binding sites by, or to displace from binding sites, other protein-bound drugs (e.g., oral anticoagulants, hydantoins, salicylates, sulfonamides, and sulfonylureas).^{125 a f} Observe for adverse effects if used with other protein-bound drugs.^a

Drugs Affecting Hepatic Microsomal Enzymes

Inhibitors of CYP2C9: possible altered safety and efficacy of mefenamic acid.¹²⁵

Specific Drugs

Drug	Interaction	Comments
ACE inhibitors	Reduced BP response to ACE inhibitor possible 125 128 b Possible deterioration of renal function in individuals with renal impairment128	Monitor BP128
Angiotensin II receptor antagonists	Reduced BP response to angiotensin II receptor antagonist possible128 Possible deterioration of renal function in individuals with renal impairment128	Monitor BP128
Antacids (magnesium-containing)	Increased peak plasma concentrations and AUC of mefenamic acid125 d
Anticoagulants (e.g., warfarin)	Possible bleeding complications125 128 a b e	Use with caution; frequent monitoring of PT advised125 128 a e
Aspirin	Increased risk of GI ulceration or other complications 125 128 b No consistent evidence that low-dose aspirin mitigates the increased risk of serious cardiovascular events associated with NSAIAs125 b	Concomitant use generally not recommended125 b
Diuretics (furosemide, thiazides)	Reduced natriuretic effects possible125 b	Monitor for diuretic efficacy and renal failure125 b
Lithium	Increased plasma lithium concentrations105 125 b	Monitor for lithium toxicity105 125 b
Methotrexate	Possible toxicity associated with increased plasma methotrexate concentrations during concomitant NSAIA use125 b	Caution advised125 b

Mefenamic Acid Pharmacokinetics

Absorption

Bioavailability

Rapidly absorbed following oral administration.^{125 a} Peak plasma concentrations usually attained within 2–4 hours.^{125 a}

Food

Effect of food on rate and extent of absorption not known.¹²⁵

Distribution

Extent

Appears to cross the placenta.^g

Distributed into milk in small amounts.^{125 c}

Plasma Protein Binding

>90%.¹²⁵

Elimination

Metabolism

Metabolized by CYP2C9 to 3′-hydroxymethyl mefenamic acid; further oxidation to 3′-carboxymefenamic acid may occur. ¹²⁵ Mefenamic acid and its metabolites also are glucuronidated.¹²⁵

Elimination Route

Excreted in urine (52%) primarily as glucuronic acid conjugates of the drug and its metabolites and in feces (<20%).¹²⁵

Half-life

Mefenamic acid: approximately 2 hours.¹²⁵ Half-lives of 3′-hydroxymethyl mefenamic acid and 3′-carboxymefenamic acid may be longer than parent compound.¹²⁵

Special Populations

Half-life 5 times longer in preterm infants compared with adults.¹²⁵

In patients with renal or hepatic impairment, clearance of metabolites may be decreased.¹²⁵

Not substantially removed by hemodialysis.^{125 a}

Stability

Storage

Oral

Capsules

20–25°C (may be exposed to 15–30°C).^{125 a}

ActionsActions

• 
  

  Inhibits cyclooxygenase-1 (COX-1) and COX-2.^{117 118 119 120 121 122}

  
  


• 
  

  Pharmacologic actions similar to those of other prototypical NSAIAs; exhibits anti-inflammatory, analgesic, and antipyretic activity.^{125 a}

  
  

Advice to Patients

• 
  

  Importance of reading the medication guide for NSAIAs that is provided to the patient each time the drug is dispensed.^{125 b}

  
  


• 
  

  Risk of serious cardiovascular events with long-term use.^{125 133 134 135 136 b} Importance of notifying clinician if signs and symptoms of a cardiovascular event (chest pain, dyspnea, weakness, slurred speech) occur.^{125 b}

  
  


• 
  

  Risk of GI bleeding and ulceration.^{100 104 125 b} Importance of notifying a clinician if signs and symptoms of serious adverse GI effects occur.^{125 b}

  
  


• 
  

  Importance of discontinuing mefenamic acid and contacting clinician if rash or other signs of hypersensitivity (blisters, fever, pruritus) develop.^{125 b} Importance of seeking immediate medical attention if an anaphylactic reaction occurs.^{125 b}

  
  


• 
  

  Risk of hepatotoxicity.^{125 b} Importance of discontinuing therapy and contacting a clinician immediately if signs and symptoms of hepatotoxicity (nausea, fatigue, lethargy, pruritus, jaundice, upper right quadrant tenderness, flu-like symptoms) occur.^{125 b}

  
  


• 
  

  Importance of notifying clinician if signs and symptoms of unexplained weight gain or edema develop.^{125 b}

  
  


• 
  

  Importance of women informing clinicians if they are or plan to become pregnant or plan to breast-feed.¹²⁵ Importance of avoiding mefenamic acid in late pregnancy (third trimester).¹²⁵

  
  


• 
  

  Importance of informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs.¹²⁵

  
  


• 
  

  Importance of informing patients of other important precautionary information.¹²⁵ (See Cautions.)

  
  

Preparations

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

* available from one or more manufacturer, distributor, and/or repackager by generic (nonproprietary) name

Mefenamic Acid

Routes	Dosage Forms	Strengths	Brand Names	Manufacturer
Oral	Capsules	250 mg*	Ponstel	First Horizon

Comparative Pricing

This pricing information is subject to change at the sole discretion of DS Pharmacy. This pricing information was updated 03/2011. Actual costs to patients will vary depending on the use of specific retail or mail-order locations and health insurance copays.

Ponstel 250MG Capsules (SHIONOGI PHARMA): 100/$1345.97 or 300/$3989.97

Disclaimer

This report on medications is for your information only, and is not considered individual patient advice. Because of the changing nature of drug information, please consult your physician or pharmacist about specific clinical use.

The American Society of Health-System Pharmacists, Inc. and Drugs.com represent that the information provided hereunder was formulated with a reasonable standard of care, and in conformity with professional standards in the field. The American Society of Health-System Pharmacists, Inc. and Drugs.com make no representations or warranties, express or implied, including, but not limited to, any implied warranty of merchantability and/or fitness for a particular purpose, with respect to such information and specifically disclaims all such warranties. Users are advised that decisions regarding drug therapy are complex medical decisions requiring the independent, informed decision of an appropriate health care professional, and the information is provided for informational purposes only. The entire monograph for a drug should be reviewed for a thorough understanding of the drug's actions, uses and side effects. The American Society of Health-System Pharmacists, Inc. and Drugs.com do not endorse or recommend the use of any drug. The information is not a substitute for medical care.

AHFS Drug Information. © Copyright, 1959-2011, Selected Revisions November 2007. American Society of Health-System Pharmacists, Inc., 7272 Wisconsin Avenue, Bethesda, Maryland 20814.

† Use is not currently included in the labeling approved by the US Food and Drug Administration.

References

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101. Food and Drug Administration. Labeling revisions for NSAIDs. FDA Drug Bull. 1989; 19:3-4.

102. Searle. Cytotec (misoprostol) prescribing information. Skokie, IL; 1989 Jan.

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106. Miller LG, Bowman RC, Bakht F. Sparing effect of sulindac on lithium levels. J Fam Prac. 1989; 28:592-3.

107. Corticosteroid interactions: nonsteroidal anti-inflammatory drugs (NSAIDs). In: Hansten PD, Horn JR. Drug interactions and updates. Vancouver, WA: Applied Therapeutics, Inc; 1993:562.

108. Garcia Rodriguez LA, Jick H. Risk of upper gastrointestinal bleeding and perforation associated with individual non-steroidal anti-inflammatory drugs. Lancet. 1994; 343:769-72. [IDIS 328176] [PubMed 7907735]

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110. Schubert TT, Bologna SD, Yawer N et al. Ulcer risk factors: interaction between Helicobacter pylori infection, nonsteroidal use, and age. Am J Med. 1993; 94:413-7. [IDIS 314155] [PubMed 8475935]

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112. Piper JM, Ray WA, Daugherty JR et al. Corticosteroid use and peptic ulcer disease: role of nonsteroidal anti-inflammatory drugs. Ann Intern Med. 1991; 114:735-40. [IDIS 280191] [PubMed 2012355]

113. Lithium interactions: diclofenac. In: Hansten PD, Horn JR. Drug interactions and updates. Vancouver, WA: Applied Therapeutics, Inc; 1993:607.

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115. Reviewers’ comments (personal observations) on diclofenac 28:08.04.

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118. Kurumbail RG, Stevens AM, Gierse JK et al. Structural basis for selective inhibition of cyclooxygenase-2 by anti-inflammatory agents. Nature. 1996; 384:644-8. [PubMed 8967954]

119. Riendeau D, Charleson S, Cromlish W et al. Comparison of the cyclooxygenase-1 inhibitory properties of nonsteroidal anti-inflammatory drugs (NSAIDs) and selective COX-2 inhibitors, using sensitive microsomal and platelet assays. Can J Physiol Pharmaco. 1997; 75:1088-95.

120. DeWitt DL, Bhattacharyya D, Lecomte M et al. The differential susceptibility of prostaglandin endoperoxide H synthases-1 and -2 to nonsteroidal anti-inflammatory drugs: aspirin derivatives as selective inhibitors. Med Chem Res. 1995; 5:325-43.

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122. Simon LS, Role and regulation of cyclooxygenase-2 during inflammation. Am J Med. 1999; 106(Suppl 5B):37-42S.

123. Morrison BW, Daniels SE, Kotey P et al. Rofecoxib, a specific cyclooxygenase-2 inhibitor, in primary dysmenorrhea: a randomized controlled study. Obstet Gynecol. 1999; 94:504-8. [IDIS 437014] [PubMed 10511349]

124. Wolfe MM, Lichtenstein DR, Singh G. Gastrointestinal toxicity of nonsteroidal antiinflammatory drugs. N Engl J Med. 1999; 340:1888-99. [IDIS 426864] [PubMed 10369853]

125. First Horizon Pharmaceutical Corporation. Ponstel (mefenamic acid) capsules prescribing information. Alpharetta, GA; 2006 Jan.

126. Singh G, Triadafilopoulos G. Epidemiology of NSAID induced gastrointestinal complications. J Rheumatol. 1999; 26(suppl 56):18-24.

127. Lanza FL, and the Ad Hoc Committee on Practice Parameters of the American College of Gastroenterology. A guideline for the treatment and prevention of NSAID-induced ulcers. Am J Gastroenterol. 1998; 93:2037-46. [IDIS 417402] [PubMed 9820370]

128. Merck & Co., Inc. Clinoril (sulindac) tablets prescribing information. Whitehouse Station, NJ; 2007 Feb.

129. Food and Drug Administration. Analysis and recommendations for agency action regarding non-steroidal anti-inflammatory drugs and cardiovascular risk. 2005 Apr 6.

130. Cush JJ. The safety of COX-2 inhibitors: deliberations from the February 16-18, 2005, FDA meeting. From the American College of Rheumatology website (). Accessed 2005 Oct 12.

131. Novartis Pharmaceuticals. Diovan (valsartan) capsules prescribing information (dated 1997 Apr). In: Physicians’ desk reference. 53rd ed. Montvale, NJ: Medical Economics Company Inc; 1999:2013-5.

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133. McGettigan P, Henry D. Cardiovascular risk and inhibition of cyclooxygenase: a systematic review of observational studies of selective and nonselective inhibitors of cyclooxygenase 2. JAMA. 2006; 296: 1633-44. [PubMed 16968831]

134. Kearney PM, Baigent C, Godwin J et al. Do selective cyclo-oxygenase-2 inhibitors and traditional non-steroidal anti-inflammatory drugs increase the risk of atherothrombosis? Meta-analysis of randomised trials. BMJ. 2006; 332: 1302-5. [PubMed 16740558]

135. Graham DJ. COX-2 inhibitors, other NSAIDs, and cardiovascular risk; the seduction of common sense. JAMA. 2006; 296:1653-6. [PubMed 16968830]

136. Chou R, Helfand M, Peterson K et al. Comparative effectiveness and safety of analgesics for osteoarthritis. Comparative effectiveness review no. 4. (Prepared by the Oregon evidence-based practice center under contract no. 290-02-0024.) . Rockville, MD: Agency for Healthcare Research and Quality. 2006 Sep. Available at: .

a. AHFS drug information 2007. McEvoy GK, ed. Mefenamic acid. Bethesda, MD: American Society of Health-System Pharmacists; 2007:2096-9.

b. US Food and Drug Administration. Proposed NSAID Package Insert Labeling Template 1. From the FDA website (). Accessed 10 Oct 2005.

c. Buchanan RA, Eaton CJ, Koeff ST et al. The breast milk excretion of mefenamic acid. Curr Ther Res Clin Exp. 1968; 10: 592-7. [PubMed 4973976]

d. Neuvonen PJ, Kivistö KT. Enhancement of drug absorption by antacids: an unrecognized drug interaction. Clin Pharmacokinet. 1994; 27:120-8. [PubMed 7955775]

e. Chan TY. Adverse interactions between warfarin and nonsteroidal antinflammatory drugs: mechanisms, clinical significance, and avoidance. Ann Pharmacother. 1995; 29:1274-83. [PubMed 8672833]

f. Diana FJ, Veronich K, Kapoor AL. Binding of nonsteroidal anti-inflammatory agents and their effect on binding of racemic warfarin and its enantiomers to human serum albumin. J Pharm Sci. 1989; 78: 195-9. [PubMed 2724076]

g. MacKenzie IZ, Graf AK, Mitchell MD. Prostaglandins in the fetal circulation following maternal ingestion of a prostaglandin synthetase inhibitor during mid-pregnancy. Int J Gynaecol Obstet. 1985; 23: 455-8. [PubMed 2868938]

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i. Anon. Drugs for rheumatoid arthritis. Med Lett Drugs Ther. 2000; 42:57-64. [PubMed 10887424]

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