Mefenamic Acid Dosage

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Usual Adult Dose for:

Usual Pediatric Dose for:

Additional dosage information:

Usual Adult Dose for Pain

500 mg orally followed by 250 mg every 6 hours as needed, not to exceed 7 days

Usual Adult Dose for Dysmenorrhea

500 mg orally followed by 250 mg every 6 hours starting with the onset of menses

Usual Pediatric Dose for Pain

14 to 18 years: 500 mg orally followed by 250 mg every 6 hours as needed, not to exceed 7 days

Renal Dose Adjustments

Use of mefenamic acid in patients with preexisting renal disease is contraindicated.

Liver Dose Adjustments

A lower dose should be considered in patients with hepatic dysfunction.

Dose Adjustments

A lower dose should be considered in the elderly.

Precautions

NSAIDs may cause an increased risk of serious cardiovascular (CV) thrombotic events, myocardial infarction, and stroke, which can be fatal. This risk may increase with duration of administration. All NSAIDs, both COX-2 selective and nonselective, may have a similar risk. Patients with CV disease or risk factors for cardiovascular disease may be at greater risk. To minimize the potential risk for an adverse CV event in patients treated with NSAIDs, the lowest effective dose should be used for the shortest duration possible. Prescribers and patients should remain vigilant for the development of such events, even in the absence of previous CV symptoms. Patients should be advised about the signs and/or symptoms of serious CV events and the steps to take if they occur. There is no consistent evidence that concurrent use of aspirin mitigates the increased risk of serious CV thrombotic events associated with NSAID use.

NSAIDs 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 serious adverse events can occur at any time, with or without warning symptoms, in patients treated with NSAIDs. Only one in five patients who develop a serious upper GI adverse event on NSAID therapy is symptomatic. It has been shown that the incidence of symptomatic upper GI ulcers, gross bleeding, or perforation, caused by NSAIDs, increases with duration of use. However, even short-term therapy is not without risk. Patients should be informed about the signs and symptoms of serious GI toxicities and the steps to take if they occur. Great caution should be exercised when using NSAIDs in patients with a prior history of peptic ulcer disease and/or GI bleeding and in patients who may have other comorbid conditions that may increase the risk of GI bleeding. Patients with a prior history of peptic ulcer disease, and/or GI bleeding, and who use NSAIDs have a greater than 10-fold increased risk for developing a GI bleed compared to patients with neither of these risk factors. Other factors that increase the risk for GI bleeding in patients treated with NSAID therapy, smoking, use of alcohol, older age, and poor general health status. Caution should be exercised when using NSAIDs in the elderly and debilitated, because most of the spontaneous reports of fatal GI adverse events are in this population. To minimize the potential risk for an adverse GI event in patients treated with an NSAID, the lowest effective dose should be used for the shortest duration. Patients and physicians should remain alert for signs and symptoms of GI ulceration and bleeding during NSAID therapy and promptly initiate additional evaluation and treatment if a serious GI adverse event is suspected. This should include discontinuation of the NSAID until a serious GI adverse event is ruled out. For high-risk patients, alternate therapies that do not involve NSAIDs should be considered.

Mefenamic acid is contraindicated for the treatment of perioperative pain in the setting of coronary artery bypass graft (CABG) surgery. In addition, the use of mefenamic acid is contraindicated in patients with preexisting renal disease, active ulceration, and chronic inflammation of the upper or lower GI tract. Mefenamic acid should not be given to patients who have experienced asthma, urticaria, or allergic-type reactions after taking aspirin or other NSAIDs. Severe, rarely fatal, anaphylactic-like reactions have been reported in this patient population.

Severe hepatic reactions, including jaundice and cases of fatal hepatitis, have been reported with mefenamic acid as with other NSAIDs. Borderline elevations of one or more liver tests have been reported in patients receiving NSAIDs. If abnormal liver tests persist or worsen, if clinical signs and symptoms consistent with liver disease develop, or if systemic manifestations occur (e.g., eosinophilia, rash, etc.), mefenamic acid should be discontinued.

Anemia has been reported in patients receiving NSAIDs, including mefenamic acid. This may be due to fluid retention, GI loss, or an effect upon erythropoiesis. Patients on long-term treatment with NSAIDs, including mefenamic acid, should have their hemoglobin and hematocrit checked if they exhibit any signs or symptoms of anemia.

NSAIDs inhibit platelet aggregation and there are reports of prolonged bleeding time in some patients. Patients taking mefenamic acid who may be adversely affected by alterations in platelet function, such as those with coagulation disorders should be carefully monitored.

Long-term administration of NSAIDs has resulted in renal papillary necrosis and other renal injury. Patients with impaired renal function, heart failure, liver dysfunction, and the elderly are at greatest risk. Renal blood flow in patients with renal dysfunction, edematous disorders, or hypovolemic states is dependent upon renal prostaglandin synthesis. Renal function may be further compromised by the use of mefenamic acid in patients with renal dysfunction, heart failure, hypovolemia, cirrhosis, nephrotic syndrome, or hypoalbuminemia. If mefenamic acid must be used, periodic monitoring of renal function is recommended. No information is available for controlled studies regarding the use of mefenamic acid in patients with advanced renal disease. Therefore, treatment is not recommended in these patients.

Caution is recommended in patients with hypertension. Blood pressure should be monitored throughout treatment.

NSAIDs may cause fluid retention and edema. Caution is recommended in patients with heart failure or preexisting fluid retention.

Adverse dermatological reactions including exfoliative dermatitis, Stevens-Johnson syndrome, and toxic epidermal necrolysis, that can be fatal, may occur without warning during NSAID treatment. Patients should be advised about the signs and symptoms of these skin manifestations. Mefenamic acid treatment should be discontinued at the first sign of rash or hypersensitivity reaction.

Patients should be adequately hydrated prior to initiation of mefenamic acid therapy.

Safety and efficacy in children younger than 14 years old have not been established.

Dialysis

Data not available

Other Comments

The dose and frequency should be adjusted to achieve an optimal response at the lowest dose possible in each patient.

Take with food or milk.

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