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Look Up > Drugs > Mefenamic Acid
Mefenamic Acid
Pronunciation
U.S. Brand Names
Generic Available
Pharmacological Index
Use
Pregnancy Risk Factor
Contraindications
Warnings/Precautions
Adverse Reactions
Overdosage/Toxicology
Drug Interactions
Mechanism of Action
Pharmacodynamics/Kinetics
Usual Dosage
Dietary Considerations
Test Interactions
Mental Health: Effects on Mental Status
Mental Health: Effects on Psychiatric Treatment
Dental Health: Local Anesthetic/Vasoconstrictor Precautions
Dental Health: Effects on Dental Treatment
Patient Information
Nursing Implications
Dosage Forms
References

Pronunciation
(me fe NAM ik AS id)

U.S. Brand Names
Ponstel®

Generic Available

No


Pharmacological Index

Nonsteroidal Anti-Inflammatory Agent (NSAID)


Use

Short-term relief of mild to moderate pain including primary dysmenorrhea


Pregnancy Risk Factor

C


Contraindications

Known hypersensitivity to mefenamic acid or other NSAIDs


Warnings/Precautions

May have adverse effects on fetus


Adverse Reactions

>10%:

Central nervous system: Dizziness

Dermatologic: Rash

Gastrointestinal: Abdominal cramps, heartburn, indigestion, nausea

1% to 10%:

Central nervous system: Headache, nervousness

Dermatologic: Itching

Endocrine & metabolic: Fluid retention

Gastrointestinal: Vomiting

Otic: Tinnitus

<1%: Congestive heart failure, hypertension, arrhythmias, tachycardia, confusion, hallucinations, aseptic meningitis, mental depression, drowsiness, insomnia, urticaria, erythema multiforme, toxic epidermal necrolysis, Stevens-Johnson syndrome, angioedema, polydipsia, hot flashes, gastritis, GI ulceration, cystitis, polyuria, agranulocytosis, anemia, hemolytic anemia, bone marrow suppression, leukopenia, thrombocytopenia, hepatitis, peripheral neuropathy, toxic amblyopia, blurred vision, conjunctivitis, dry eyes, decreased hearing, acute renal failure, shortness of breath, allergic rhinitis, epistaxis


Overdosage/Toxicology

Symptoms of overdose include CNS stimulation, agitation, seizures

Management of a nonsteroidal anti-inflammatory drug (NSAID) intoxication is primarily supportive and symptomatic. Fluid therapy is commonly effective in managing the hypotension that may occur following an acute NSAIDs overdose, except when this is due to an acute blood loss. Seizures tend to be very short-lived and often do not require drug treatment. Although, recurrent seizures should be treated with I.V. diazepam. Since many of the NSAID undergo enterohepatic cycling, multiple doses of charcoal may be needed to reduce the potential for delayed toxicities.


Drug Interactions

CYP2C9 enzyme substrate

Increased effect/toxicity with oral anticoagulants, methotrexate


Mechanism of Action

Inhibits prostaglandin synthesis by decreasing the activity of the enzyme, cyclo-oxygenase, which results in decreased formation of prostaglandin precursors


Pharmacodynamics/Kinetics

Peak effect: Oral: Within 2-4 hours

Duration of action: Up to 6 hours

Protein binding: High

Metabolism: Conjugated in the liver

Half-life: 3.5 hours

Elimination: In urine (50%) and feces as unchanged drug and metabolites


Usual Dosage

Children >14 years and Adults: Oral: 500 mg to start then 250 mg every 4 hours as needed; maximum therapy: 1 week


Dietary Considerations

May be administered with food, milk, or antacids


Test Interactions

chloride (S), sodium (S), positive Coombs' [direct], false-positive urinary bilirubin


Mental Health: Effects on Mental Status

Dizziness is common; may cause nervousness, may rarely cause confusion, hallucination, or depression


Mental Health: Effects on Psychiatric Treatment

May rarely cause agranulocytosis; use caution with clozapine or carbamazepine; may decrease lithium clearance resulting in an increase in serum lithium levels and potential lithium toxicity; monitor serum lithium levels


Dental Health: Local Anesthetic/Vasoconstrictor Precautions

No information available to require special precautions


Dental Health: Effects on Dental Treatment

NSAID formulations are known to reversibly decrease platelet aggregation via mechanisms different than observed with aspirin. The dentist should be aware of the potential of abnormal coagulation. Caution should also be exercised in the use of NSAIDs in patients already on anticoagulant therapy with drugs such as warfarin (Coumadin®). Recovery of platelet function usually occurs 1-2 days after discontinuation of NSAIDs.


Patient Information

Take with food, milk, or with antacids; extended release capsules must be swallowed intact


Nursing Implications

Extended release capsules must be swallowed intact


Dosage Forms

Capsule: 250 mg


References

Balali-Mood M, Critchley JA, Proudfoot AT, et al, "Mefenamic Acid Overdosage," Lancet, 1981, 2(8234):1354-6.

Brooks PM and Day RO, "Nonsteroidal Anti-inflammatory Drugs - Differences and Similarities," N Engl J Med, 1991, 324(24):1716-25.

Clinch D, Banerjee AK, Ostick G, "Absence of Abdominal Pain in Elderly Patients With Peptic Ulcer," Age Ageing, 1984, 13:120-3.

Clive DM, Stoff JS, "Renal Syndromes Associated With Nonsteroidal Anti-inflammatory Drugs," N Engl J Med, 1984, 310(9):563-72.

Court H and Volans GN, "Poisoning After Overdose With Nonsteroidal Anti-inflammatory Drugs," Adverse Drug React Acute Poisoning Rev, 1984, 3(1):1-21.

"Drugs for Pain," Med Lett Drugs Ther, 1998, 40(1033):79-84.

Gossinger H, Hruby K, Haubenstock A, et al, "Coma in Mefenamic Acid Poisoning," Lancet, 1982, 2(8294):384.

Graham DY, "Prevention of Gastroduodenal Injury Induced by Chronic Nonsteroidal Anti-inflammatory Drug Therapy," Gastroenterology, 1989, 96(2 Pt 2 Suppl):675-81.

Gurwitz JH, Avorn J, Ross-Degnan D, et al, "Nonsteroidal Anti-Inflammatory Drug-Associated Azotemia in the Very Old," JAMA, 1990, 264(4):471-5.

Hawkey CJ, Karrasch JA, Szczepanski L, et al, "Omeprazole Compared With Misoprostrol for Ulcers Associated With Nonsteroidal Anti-inflammatory Drugs," N Engl J Med, 1998, 338(11):727-34.

Hendrickse MT, "Mefenamic Acid Overdose Mimicking Brainstem Stroke," Lancet, 1988, 2(8618):1019.

Hoppmann RA, Peden JG, and Ober SK, "Central Nervous System Side Effects of Nonsteroidal Anti-inflammatory Drugs. Aseptic Meningitis, Psychosis, and Cognitive Dysfunction," Arch Intern Med, 1991, 151(7):1309-13.

Pounder R, "Silent Peptic Ulceration: Deadly Silence or Golden Silence?" Gastroenterology, 1989, 96(2 Pt 2 Suppl):626-31.

Shipton EA and Muller FO, "Severe Mefenamic Acid Poisoning. A Case Report," S Afr Med J, 1985, 67(20):823-4.

Smolinske SC, Hall AH, Vandenberg SA, et al, "Toxic Effects of Nonsteroid Anti-inflammatory Drugs in Overdose. An Overview of Recent Evidence on Clinical Effects and Dose-Response Relationships," Drug Saf, 1990, 5(4):252-74.

Turnbull AJ, Campbell P, and Hughes JA, "Mefenamic Acid Nephropathy - Acute Renal Failure in Overdose," Br Med J (Clin Res Ed), 1988, 296(6622):646.

Vale JA and Meredith TJ, "Acute Poisoning Due to Nonsteroidal Anti-inflammatory Drugs," Med Toxicol, 1986, 1(1):12-31.

Verbeeck RK, "Pharmacokinetic Drug Interactions With Nonsteroidal Anti-inflammatory Drugs," Clin Pharmacokinet, 1990, 19(1):44-66.

Yeomans ND, Tulassay Z, Juhasz L, et al, "A Comparison of Omeprazole With Ranitidine for Ulcers Associated With Nonsteroidal Anti-inflammatory Drugs," N Engl J Med, 1998, 338(11):719-26.


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