Brand Names

MEFENAMIC ACID
PONSTEL

Boxed Warning

WARNING: RISK OF SERIOUS CARDIOVASCULAR and GASTROINTESTINAL EVENTS Cardiovascular Thrombotic Events Nonsteroidal anti-inflammatory drugs (NSAIDs) cause an increased risk of serious cardiovascular thrombotic events, including myocardial infarction and stroke, which can be fatal. This risk may occur early in treatment and may increase with duration of use [see Warnings and Precautions (5.1)]. Mefenamic acid is contraindicated in the setting of coronary artery bypass graft (CABG) surgery [see Contraindications (4), see Warnings and Precautions (5.1)]. Gastrointestinal Bleeding, Ulceration, and Perforation 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 events can occur at any time during use and without warning symptoms. Elderly patients and patients with a prior history of peptic ulcer disease and/or GI bleeding are at greater risk for serious GI events [see Warnings and Precautions (5.2)].

Contraindications

Mefenamic acid capsules are contraindicated in the following patients: Known hypersensitivity (e.g., anaphylactic reactions and serious skin reactions) to mefenamic acid or any components of the drug product [see Warnings and Precautions (5.7)]. History of asthma, urticaria, or other allergic-type reactions after taking aspirin or other NSAIDs. Severe, sometimes fatal, anaphylactic reactions to NSAIDs have been reported in such patients [see Warnings and Precautions (5.7, 5.8, 5.9)]. In the setting of coronary artery bypass graft (CABG) surgery [see Warnings and Precautions (5.1)].

Adverse Reactions

The following adverse reactions are discussed in greater detail in other sections of the labeling: Cardiovascular Thrombotic Events [see Warnings and Precautions (5.1)] GI Bleeding, Ulceration and Perforation [see Warnings and Precautions (5.2)] Hepatotoxicity [see Warnings and Precautions (5.3)] Hypertension [see Warnings and Precautions (5.4)] Heart Failure and Edema [see Warnings and Precautions (5.5)] Renal Toxicity and Hyperkalemia [see Warnings and Precautions (5.6)] Anaphylactic Reactions [see Warnings and Precautions (5.7)] Serious Skin Reactions [see Warnings and Precautions (5.9, 5.10)] Hematologic Toxicity [see Warnings and Precautions (5.12)] Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. The following adverse reactions associated with the use of mefenamic acid were identified in clinical studies or post- marketing reports. Because some of these reactions were reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure In patients taking mefenamic acid or other NSAIDs, the most frequently reported adverse reactions occurring in approximately 1 to10 % of patients are: Gastrointestinal - Abdominal pain, constipation, diarrhea, dyspepsia, flatulence, gross bleeding/perforation, heartburn, nausea, GI ulcers (gastric/duodenal), vomiting Auditory System - Tinnitus Genitourinary System - Abnormal renal function Hepatic System - Elevated liver enzymes Dermatologic - Pruritus, rashes Cardiovascular - Anemia, edema Central Nervous System - Dizziness, headache Hematopoetic and lymphatic system - Increased bleeding time Additional adverse experiences reported less frequently and listed here by body system include: General - anaphylactoid reac

Drug Interactions

See Table 1 for clinically significant drug interactions with mefenamic acid. Table1: Clinically Significant Drug Interactions with Mefenamic Acid Drugs That Interfere with Hemostasis Clinical Impact: Mefenamic acid and anticoagulants such as warfarin have a synergistic effect on bleeding. The concomitant use of mefenamic acid and anticoagulants have an increased risk of serious bleeding compared to the use of either drug alone. Serotonin release by platelets plays an important role in hemostasis. Case-control and cohort epidemiological studies showed that concomitant use of drugs that interfere with serotonin reuptake and an NSAID may potentiate the risk of bleeding more than an NSAID alone. Intervention: Monitor patients with concomitant use of mefenamic acid with anticoagulants (e.g., warfarin), antiplatelet agents (e.g., aspirin), selective serotonin reuptake inhibitors (SSRIs), and serotonin norepinephrine reuptake inhibitors (SNRIs) for signs of bleeding [see Warnings and Precautions (5.12)] . Aspirin Clinical Impact: Controlled clinical studies showed that the concomitant use of NSAIDs and analgesic doses of aspirin does not produce any greater therapeutic effect than the use of NSAIDs alone. In a clinical study, the concomitant use of an NSAID and aspirin was associated with a significantly increased incidence of GI adverse reactions as compared to use of the NSAID alone [see Warnings and Precautions (5.2)] . Intervention: Concomitant use of mefenamic acid and analgesic doses of aspirin is not generally recommended because of the increased risk of bleeding [see Warnings and Precautions (5.12)] . Mefenamic acid is not a substitute for low dose aspirin for cardiovascular protection. ACE Inhibitors, Angiotensin Receptor Blockers, and Beta-Blockers Clinical Impact: NSAIDs may diminish the antihypertensive effect of angiotensin converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs), or beta-blockers (including propranolol). In patients who are e

Mechanism of Action

Mefenamic acid has analgesic, anti-inflammatory, and antipyretic properties. The mechanism of action of mefenamic acid, like that of other NSAIDs, is not completely understood but involves inhibition of cyclooxygenase (COX-1 and COX-2). Mefenamic acid is a potent inhibitor of prostaglandin synthesis in vitro. Mefenamic acid concentrations reached during therapy have produced in vivo effects. Prostaglandins sensitize afferent nerves and potentiate the action of bradykinin in inducing pain in animal models. Prostaglandins are mediators of inflammation. Because mefenamic acid is an inhibitor of prostaglandin synthesis, its mode of action may be due to a decrease of prostaglandins in peripheral tissues.

Overdosage

Symptoms following acute NSAID overdosages have been typically limited to lethargy, drowsiness, nausea, vomiting, and epigastric pain, which have been generally reversible with supportive care. Gastrointestinal bleeding has occurred. Hypertension, acute renal failure, respiratory depression, and coma have occurred but were rare [see Warnings and Precautions (5.1, 5.2, 5.4, 5.6)]. Manage patients with symptomatic and supportive care following an NSAID overdosage. There are no specific antidotes. Consider emesis and/or activated charcoal (60 to 100 grams in adults, 1 to 2 grams per kg of body weight in pediatric patients) and/or osmotic cathartic in symptomatic patients seen within four hours of ingestion or in patients with a large overdose (5 to 10 times the recommended dosage). Forced diuresis, alkalinization of urine, hemodialysis, or hemoperfusion may not be useful due to high protein binding. For additional information about overdosage treatment, contact a Poison Help Line (1-800-222-1222).

⚠ Caution

Medical Disclaimer: This information is for educational purposes only. Always consult a healthcare professional before taking any medication.