Mefenamic acid
Mechanism :
It is an NSAID and used as an analgesic in the treatment of painful musculoskeletal problems, chronic JRA.
Indication :
- Menstrual pain
- Musculoskeletal pain
- Fever
- Rheumatoid arthritis
- Osteoarthritis
- Relief of pain with inflammation
Contraindications :
Hypersensitive to drug/class/component.
ASA or NSAID-induced asthma or urticaria, Aspirin triad, Pregnancy 3rd trimester, Renal disease, CABG surgery periop use, Active PUD.
Caution if Prolonged use, Bleeding from ulcer, Cardiovascular, renal or hepatic disease, Anticoagulant use or Coagulation disorder, Asthma, Diuretic use.
Dosing :
<14 years:
Not recommended.
≥14 years:
Initial 500 mg orally once, then 250 mg PO every 6 hours as needed usually not more than 7 days in pain and not more than 3 days in primary dysmenorrhea.
Adverse Effect :
Serious Reactions: Hypertension, GI bleeding, hepatotoxicity, stroke, thromboembolism, GI perforation/ulcer, Stevens-Johnson syndrome, congenital hepatic fibrosis, renal papillary necrosis, myocardial infarction, blood dyscrasias, nephrotoxicity, bronchospasm, anaphylactoid reaction, exfoliative dermatitis, anemia, toxic epidermal necrolysis.
Common Reactions: dizziness, dyspepsia, elevated ALT/AST, fluid retention, ecchymosis, tinnitus, headache, somnolence, rash, peripheral edema, photosensitivity, abdominal pain, anorexia, diarrhea, nausea, gastritis, flatulence, constipation, steatorrhea, upper GI ulcers.
Interaction :
Acenocoumarol: The NSAID, mefenamic acid, may increase the anticoagulant effect of acenocoumarol.
Alendronate: Increased risk of gastric toxicity.
Anisindione: The NSAID, mefenamic acid, may increase the anticoagulant effect of anisindione.
Azilsartan medoxomil: Increases toxicity of each. May deteriorate renal function, particularly in volume depleted or elderly patients. Decreases effects of azilsartan by antagonism.
Colesevelam: Bile acid sequestrants may decrease the absorption of Nonsteroidal Anti-Inflammatory Agents. Monitor for decreased serum concentrations/therapeutic effects of nonsteroidal anti-inflammatory agents (NSAID) if coadministered with bile acid sequestrants. Separating the administration of doses by 2 or more hours may reduce (but not eliminate) the risk of interaction.
Cyclosporine: Monitor for nephrotoxicity.
Dicoumarol: The NSAID, mefenamic acid, may increase the anticoagulant effect of dicumarol.
Eltrombopag: Increases levels of Mefenamic acid via metabolism decrease. UDP-glucuronosyltransferase inhibition with unclear significance.
Lithium: The NSAID, mefenamic acid, may decrease the renal excretion of lithium. Increased risk of lithium toxicity.
Methotrexate: The NSAID, mefenamic acid, may decrease the renal excretion of methotrexate. Increased risk of methotrexate toxicity.
Tamoxifen: Mefenamic acid may reduce clearance rate of Tamoxifen. Monitor for changes in therapeutic/adverse effects of Tamoxifen if Mefenamic acid is initiated, discontinued or dose changed.
Tolbutamide: Mefenamic acid, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Tolbutamide, a CYP2C9 substrate. Consider alternate therapy or monitor for changes in Tolbutamide therapeutic and adverse effects if Mefenamic acid is initiated, discontinued or dose changed.
Torasemide: Mefenamic acid, a strong CYP2C9 inhibitor, may increase the serum concentration of Torasemide, a CYP2C9 substrate, by decreasing Torasemide metabolism and clearance. Consider alternate therapy or monitor for changes in the therapeutic and adverse effects of Torasemide if Mefenamic acid is initiated, discontinued or dose changed.
Trandolapril: The NSAID, Mefenamic acid, may reduce the antihypertensive effect of Trandolapril. Consider alternate therapy or monitor for changes in Trandolapril efficacy if Mefenamic acid is initiated, discontinued or dose changed.
Treprostinil: The prostacyclin analogue, Treprostinil, may increase the risk of bleeding when combined with the NSAID, Mefenamic acid. Monitor for increased bleeding during concomitant therapy.
Trimethoprim: The strong CYP2C9 inhibitor, Mefenamic acid, may decrease the metabolism and clearance of Trimethoprim, a CYP2C9 substrate. Consider alternate therapy or monitor for changes in therapeutic and adverse effects of Trimethoprim if Mefenamic acid is initiated, discontinued or dose changed.
Voriconazole: Mefenamic acid, a strong CYP2C9 inhibitor, may increase the serum concentration of voriconazole by decreasing its metabolism. Monitor for changes in the therapeutic and adverse effects of voriconazole if mefenamic acid is initiated, discontinued or dose changed.
Warfarin: Mefenamic acid, a strong CYP2C9 inhibitor, may decrease the metabolism of warfarin. The antiplatelet effect of mefenamic acid may also increase the bleed risk associated with warfarin. Consider alternate therapy or monitor for changes in the therapeutic and adverse effects of warfarin if mefenamic acid is initiated, discontinued or dose changed.
Renal Dose :
Dose in Renal Impairment GFR (mL/min)
| 20-50 | Dose as in normal renal function, but avoid if possible |
| 10-20 | Dose as in normal renal function, but avoid if possible |
| <10 | Dose as in normal renal function, but only use if on dialysis |
Dose in Patients undergoing Renal Replacement Therapies
| CAPD | Unlikely to be dialysed. Dose as in normal renal function |
| HD | Not dialysed. Dose as in normal renal function. |
| HDF/High flux | Unknown dialysability. Dose as in normal renal function. |
| CAV/VVHD | Unlikely to be dialysed. Dose as in GFR=10–20 mL/min |
Hepatic Dose :
Reduce the dose in hepatic impairment.