What is Indomethacin?
Indomethacin is a potent nonsteroidal anti-inflammatory drug (NSAID) that works by inhibiting prostaglandin synthesis, providing antipyretic, analgesic, and anti-inflammatory effects for conditions like acute gout, rheumatoid arthritis, ankylosing spondylitis, and osteoarthritis. 1
Mechanism of Action
Indomethacin functions as a potent inhibitor of prostaglandin synthesis, blocking the cyclooxygenase (COX) enzyme pathway. 1 This inhibition decreases prostaglandins in peripheral tissues, which are key mediators of inflammation and pain. Prostaglandins sensitize nerve endings and amplify bradykinin's pain-inducing effects, so blocking their production provides significant anti-inflammatory and analgesic benefits. 1
The drug is classified as a nonselective COX inhibitor, meaning it blocks both COX-1 and COX-2 enzymes. 2 This differs from selective COX-2 inhibitors and explains both its efficacy and its side effect profile.
Pharmacokinetics
- Absorption: Virtually 100% bioavailable orally, with peak plasma concentrations reached at approximately 2 hours after administration 1
- Distribution: Approximately 99% protein-bound in plasma; crosses the blood-brain barrier and placenta 1
- Metabolism: Undergoes extensive hepatic metabolism to inactive metabolites with appreciable enterohepatic circulation 1
- Elimination: Half-life of approximately 4.5 hours; 60% recovered in urine (26% as unchanged drug and glucuronide), 33% in feces 1
Clinical Indications
Acute Gout
Indomethacin has been historically considered first-line NSAID therapy for acute gout, though moderate-quality evidence shows no difference in efficacy compared to other NSAIDs like naproxen or ibuprofen. 3 The 2017 American College of Physicians guidelines explicitly state there is no evidence that indomethacin is more efficacious than other NSAIDs for gout treatment. 3
Chronic Inflammatory Conditions
- Rheumatoid arthritis: Reduces joint swelling, morning stiffness, and improves functional capability 1
- Ankylosing spondylitis: Effective for long-term management 1
- Osteoarthritis: Provides symptom relief without altering disease progression 1
Indomethacin-Responsive Headaches
Indomethacin is uniquely effective for specific headache disorders including paroxysmal hemicrania and hemicrania continua, where it serves as both a diagnostic and therapeutic tool. 4, 5
Important Safety Considerations
Gastrointestinal Risks
NSAIDs including indomethacin carry risk for dyspepsia, gastrointestinal perforations, ulcers, and bleeding. 3 In comparative studies, indomethacin showed higher rates of gastrointestinal adverse events (63%) compared to corticosteroids (27%) in gout treatment. 6
Contraindications
Indomethacin should be avoided or used with extreme caution in patients with:
- Renal disease (contraindicated in severe renal impairment with GFR <30 mL/min) 3, 7
- Heart failure 3
- Cirrhosis 3
- Active peptic ulcer disease or GI bleeding history
Drug Interactions
Special attention required when co-prescribed with:
- Statins 7
- P-glycoprotein inhibitors (cyclosporin, clarithromycin, verapamil, ketoconazole) 7
- CYP3A4 inhibitors 7
Clinical Context: The Indomethacin Myth in Gout
A critical clinical pitfall is the persistent belief that indomethacin is superior to other NSAIDs for acute gout. This is explicitly contradicted by current evidence. 3 The 2017 ACP guidelines make clear that corticosteroids should actually be considered first-line therapy for acute gout in patients without contraindications, as they are generally safer with fewer adverse effects than NSAIDs. 3
When NSAIDs are chosen for gout, any NSAID at appropriate anti-inflammatory doses is equally effective—the choice should be based on patient-specific factors including contraindications, prior response, cost, and comorbidities. 3, 8
Dosing Considerations
For acute conditions, indomethacin is typically dosed at 25-50 mg three times daily, with steady-state plasma concentrations averaging 1.4 times those after the first dose. 1 Sustained-release formulations allow for once or twice daily dosing with comparable efficacy. 9