Indomethacin (Indocin)
indomethacin
Indications
| Indication | Approved Population | Therapy Type | Status |
|---|---|---|---|
| Moderate to severe rheumatoid arthritis | Adults | Monotherapy or adjunctive | FDA Approved |
| Moderate to severe ankylosing spondylitis | Adults | Monotherapy | FDA Approved |
| Moderate to severe osteoarthritis | Adults | Monotherapy | FDA Approved |
| Acute painful shoulder (bursitis/tendinitis) | Adults | Short-term (7–14 days) | FDA Approved |
| Acute gouty arthritis | Adults (IR only; not SR) | Short-term until pain resolves | FDA Approved |
| Patent ductus arteriosus (PDA) | Premature neonates (IV formulation) | Monotherapy | FDA Approved |
Indomethacin is one of the oldest and most potent non-selective NSAIDs, first approved in 1965. As an indoleacetic acid derivative, it is a powerful inhibitor of both COX-1 and COX-2, making it highly effective for severe inflammatory conditions but also associated with a higher adverse effect burden than many other NSAIDs, particularly regarding CNS and GI toxicity. Its high lipophilicity enables it to cross the blood-brain barrier, which accounts for its distinctive CNS side effect profile (headache, dizziness, drowsiness, and rarely confusion or psychosis in the elderly). Indomethacin remains a first-line option for acute gout flares and is uniquely approved for PDA closure in neonates via the IV route. The FDA PI specifically warns that persistent headache despite dose reduction mandates cessation of the drug.
Prevention of post-ERCP pancreatitis — Rectal indomethacin 100 mg is strongly recommended by multiple guidelines (ESGE, ACG) for prevention of post-ERCP pancreatitis in all patients undergoing ERCP. Evidence quality: High.
Recurrent pericarditis — Indomethacin is used in combination with colchicine for treatment of recurrent pericarditis, supported by ESC guidelines. Evidence quality: Moderate.
Hemicrania continua / paroxysmal hemicrania — Indomethacin is considered diagnostic and therapeutic for these trigeminal autonomic cephalalgias; complete response to indomethacin is a diagnostic criterion. Evidence quality: High.
Preterm labour tocolysis — Used short-term (<48 h, <32 weeks gestation) to inhibit premature contractions; limited by fetal ductus concerns. Evidence quality: Moderate.
Dosing
Adult Oral Dosing by Clinical Scenario
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| RA / AS / OA — chronic management | 25 mg BID–TID | Increase by 25–50 mg/week to response | 150–200 mg/day | Doses above 150–200 mg generally do not increase efficacy; give large portion at bedtime for night pain/morning stiffness (max 100 mg at bedtime) Reduce dose after acute flare is controlled |
| RA / AS / OA — SR formulation | 75 mg once daily | 75 mg once or twice daily | 150 mg/day | SR may substitute for IR in RA/AS/OA but NOT for acute gout Swallow whole; do not crush or chew |
| Acute gouty arthritis | 50 mg TID | Reduce rapidly once pain tolerable | 150 mg/day | Relief within 2–4 h; tenderness/heat subside in 24–36 h; swelling resolves in 3–5 days; rapidly taper to cessation Use IR capsules only (not SR) |
| Acute painful shoulder (bursitis/tendinitis) | 25 mg TID–QID | 75–150 mg/day in 3–4 divided doses | 150 mg/day | Discontinue after symptoms controlled for several days; usual course 7–14 days |
| Post-ERCP pancreatitis prevention (off-label) | 100 mg PR single dose | Single dose immediately before or after ERCP | 100 mg single dose | Rectal administration; supported by ESGE/ACG guidelines; evidence from multiple RCTs |
Pediatric Dosing
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| JRA (≥2 years; only if other drugs warrant risk) | 1–2 mg/kg/day divided | 1–2 mg/kg/day in divided doses | 3 mg/kg/day or 150–200 mg/day (whichever is less) | Not recommended for patients ≤14 years unless other therapies have failed; cases of fatal hepatotoxicity in paediatric JRA reported Monitor LFTs periodically; limited data for 4 mg/kg/day |
Indomethacin occupies a unique niche in headache medicine. Complete responsiveness to indomethacin is a diagnostic criterion for hemicrania continua, paroxysmal hemicrania, and primary stabbing headache. If a patient with a unilateral continuous headache responds dramatically and completely to indomethacin (typically 25 mg TID, titrated up to 75 mg TID if needed), this effectively confirms the diagnosis. Paradoxically, indomethacin itself commonly causes headache as a side effect — persistent headache despite dose reduction mandates drug cessation per the FDA PI.
Special Population Adjustments
| Population | Adjustment | Rationale |
|---|---|---|
| Hepatic impairment | Use with caution; PK not studied | Hepatic metabolism is a major elimination pathway |
| Renal impairment | Avoid in advanced renal disease; PK not studied | Triamterene combination is CONTRAINDICATED (acute renal failure in 2/4 healthy volunteers) |
| Elderly (≥65 years) | Use greater care; start at lowest dose | Increased CNS adverse effects (confusion, psychosis); increased GI, CV, and renal risk |
Pharmacology
Mechanism of Action
Indomethacin is an indoleacetic acid derivative that potently inhibits both cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2), resulting in broad suppression of prostaglandin synthesis. It is among the most potent non-selective NSAIDs, which accounts for both its high anti-inflammatory efficacy and its significant adverse effect profile. Indomethacin’s high lipophilicity enables it to readily cross the blood-brain barrier, producing central nervous system effects (headache, dizziness, drowsiness) that are more prominent than with other NSAIDs. Its ability to close the patent ductus arteriosus in neonates is mediated through inhibition of ductal prostaglandin E2 synthesis. Indomethacin has also been reported to diminish cerebral blood flow via prostaglandin inhibition, though this effect appears transient with continued oral dosing.
ADME Profile
| Parameter | Value | Clinical Implication |
|---|---|---|
| Absorption | Virtually 100% bioavailable; 90% absorbed within 4 h; Tmax ~2 h; peak plasma ~1 mcg/mL (25 mg) and ~2 mcg/mL (50 mg); suppositories absorbed more rapidly but total absorption 80–90% of capsules | Complete oral absorption; take with food, after meals, or with antacids for GI tolerability (PI recommendation); rectal route provides faster absorption but slightly lower total bioavailability |
| Distribution | ~99% albumin-bound; crosses blood-brain barrier and placenta; appears in breast milk; high concentrations in synovial fluid; steady-state levels 1.4× first dose | BBB penetration explains CNS effects (headache, dizziness, confusion); synovial fluid persistence supports anti-inflammatory action despite moderate plasma half-life |
| Metabolism | Hepatic: O-demethylation, deacetylation, and glucuronidation; major metabolites include O-desmethyl-indomethacin and O-deschloro-benzoyl-indomethacin; appreciable enterohepatic circulation | Enterohepatic recycling produces variable effective half-life (reported range 1.5–16 h in literature); specific CYP enzyme roles less characterised than for diclofenac; PK not studied in hepatic impairment |
| Elimination | Mean t½ ~4.5 h (FDA PI); ~60% urine (26% as indomethacin + glucuronide), ~33% faeces (1.5% as indomethacin); no significant accumulation with repeated dosing | Moderate half-life supports TID dosing; enterohepatic circulation may extend effective duration; renal impairment PK not studied — caution warranted |
Side Effects
Adverse reactions generally correlate with dose. The most common adverse reactions (≥3%) are headache, dizziness, dyspepsia, and nausea (FDA PI). Incidence data below derived from 33 double-blind controlled clinical trials involving 1,092 patients. Indomethacin has a notably higher rate of CNS adverse effects (headache, dizziness, drowsiness, confusion) than other NSAIDs, attributable to its BBB penetration.
| Adverse Effect | Incidence | Clinical Note |
|---|---|---|
| Headache | 3–9% | Distinctive to indomethacin; may be persistent and severe; if headache persists despite dose reduction, drug must be STOPPED per PI |
| Dizziness | 3–9% | CNS effect from BBB penetration; advise caution with driving; more common than with other NSAIDs |
| Dyspepsia | 3–9% | Take with food or antacids; co-prescribe PPI in high-risk patients |
| Nausea (with or without vomiting) | 3–9% | Dose-related; may improve with dose reduction or food |
| Drowsiness / somnolence | 1–3% | CNS effect; may impair driving and operating machinery; caution patients |
| Abdominal pain / distress | 1–3% | Evaluate for ulceration if persistent |
| Diarrhoea / constipation | 1–3% | GI complaints more frequent than with some newer NSAIDs |
| Tinnitus | 1–3% | Usually reversible with dose reduction |
| Peripheral edema | 1–3% | Monitor weight and BP; caution in heart failure |
| Depression / fatigue | 1–3% | CNS effect; monitor mood especially in elderly |
| Adverse Effect | Estimated Frequency | Typical Onset | Required Action |
|---|---|---|---|
| Cardiovascular thrombotic events (MI, stroke) | NSAID class risk; may begin early in treatment | First weeks; increases with dose and duration | Use lowest effective dose for shortest duration; avoid post-CABG |
| GI bleeding, ulceration, perforation | ~1% at 3–6 months; 2–4% at 1 year (NSAID class) | Any time; without warning | Discontinue immediately; urgent endoscopy; add PPI prophylaxis in high-risk patients |
| Hepatotoxicity (severe) | Rare; ALT >3× ULN in <1%; up to 15% with borderline elevations; fatal cases in paediatric JRA | 1–8 weeks typically; can be 4–6 months | Discontinue if persistent or symptomatic; periodic LFTs especially in paediatric JRA patients |
| CNS effects (confusion, psychosis, depersonalisation) | Rare; more common in elderly | Days to weeks | Discontinue if severe CNS adverse reactions develop (FDA PI) |
| Corneal deposits / retinal disturbances | Rare (reported with chronic use) | Months of use | Ophthalmological examination if visual complaints; discontinue if changes confirmed |
| Acute kidney injury / renal papillary necrosis | Uncommon; higher with dehydration or concurrent triamterene | Days to weeks | Discontinue; never co-administer with triamterene; IV hydration |
| Severe skin reactions (SJS, TEN, DRESS) | Very rare | 1–8 weeks | Discontinue immediately; dermatology referral |
| Heart failure exacerbation | ~2-fold increased hospitalisation (NSAID class) | Days to weeks | Avoid in severe HF; monitor fluid balance |
The FDA PI includes specific warnings (sections 5.15 and 5.16) that are unique to indomethacin among oral NSAIDs. Indomethacin may cause drowsiness, and patients should be cautioned about driving. Headache that persists despite dose reduction requires cessation of the drug. Corneal deposits and retinal disturbances have been reported with prolonged use and ophthalmological examination is recommended if visual complaints arise. In the elderly, confusion and even psychosis have been reported rarely — physicians should remain alert to these possibilities.
Drug Interactions
Indomethacin undergoes enterohepatic circulation and hepatic metabolism. Its most clinically distinctive interaction is a CONTRAINDICATION with triamterene, which caused reversible acute renal failure in 2 of 4 healthy volunteers. Chronic aspirin co-administration reduces indomethacin levels by approximately 20%. Diflunisal significantly increases indomethacin plasma levels.
Monitoring
- CNS SymptomsEvery visit; urgently if new symptoms
RoutineAsk about headache (persistent headache mandates cessation per PI), dizziness, drowsiness, confusion, mood changes. Particularly important in elderly where psychosis has been reported. - Hepatic FunctionBaseline; periodically during chronic use
RoutineALT/AST. Borderline elevations in up to 15% of NSAID-treated patients; ALT >3× ULN in <1%. Fatal hepatotoxicity reported in paediatric JRA — mandatory periodic LFTs in children. - Blood PressureBaseline, then periodically
RoutineNSAIDs including indomethacin can elevate BP and impair response to antihypertensives. - Renal FunctionBaseline, then q6–12 months
RoutineCreatinine, BUN, eGFR. PK not studied in renal impairment — monitor closely. Never co-administer with triamterene. - CBCBaseline; then if signs of anaemia or bleeding
Trigger-basedMonitor for occult GI blood loss. Chemistry profile periodically for long-term use per PI. - OphthalmologicalIf visual complaints arise
Trigger-basedCorneal deposits and retinal disturbances reported (PI section 5.16). Examine if blurred vision, visual disturbance, or eye pain develops.
Contraindications & Cautions
Absolute Contraindications
- Known hypersensitivity to indomethacin or any component
- Aspirin-exacerbated respiratory disease (AERD)
- Peri-operative CABG surgery setting
- Concurrent triamterene — acute renal failure reported (PI-specific contraindication)
- Pregnancy ≥30 weeks gestation
- Previous serious skin reactions to NSAIDs
Relative Contraindications (Specialist Input Recommended)
- Advanced renal disease — PK not studied; avoid unless benefits outweigh risk
- Active peptic ulcer or recent GI bleed
- Severe heart failure (NYHA III–IV)
- Pre-existing psychiatric conditions in elderly — confusion/psychosis risk
- Pregnancy 20–30 weeks — limit use
Use with Caution
- Elderly (≥65 years) — greater care needed per PI; increased CNS, GI, CV, and renal risk
- Paediatric patients ≤14 years — only if other drugs warrant the risk; fatal hepatotoxicity reported
- Concurrent anticoagulants, SSRIs, corticosteroids — additive bleeding risk
- Epilepsy, parkinsonism, psychiatric illness — CNS effects may exacerbate
- Dehydration or hypovolaemia — correct volume status before starting
Cardiovascular Thrombotic Events: NSAIDs cause an increased risk of serious cardiovascular thrombotic events, including myocardial infarction and stroke, which can be fatal. This risk may begin early in treatment and increase with duration of use. Indomethacin is contraindicated in the setting of CABG surgery.
Gastrointestinal Bleeding, Ulceration, and Perforation: NSAIDs cause an increased risk of serious GI adverse events which can be fatal. These events can occur at any time without warning. Elderly patients and those with prior peptic ulcer disease or GI bleeding are at greater risk.
Patient Counselling
Purpose of Therapy
Indomethacin is a powerful anti-inflammatory medicine used to reduce pain, swelling, and stiffness. It works quickly for acute gout (often within 2–4 hours) and is also used for chronic arthritis. Because it is stronger than many other anti-inflammatory drugs, it may cause more side effects, especially headache and dizziness.
How to Take
Take with food, immediately after meals, or with antacids to reduce stomach upset. Swallow extended-release capsules whole. If using oral suspension, shake well before each dose. For acute gout, your doctor will instruct you to stop the medicine once pain resolves — do not continue longer than necessary.
Sources
- Indomethacin Capsules — Full Prescribing Information. Revised 04/2021. Reference ID: 4786627. accessdata.fda.govPrimary source for all approved oral indications, dosing (RA/AS/OA, gout, bursitis), adverse reactions from 33 controlled trials (N=1,092), PK data (t½ ~4.5 h, bioavailability ~100%), and CNS/ocular effect warnings (sections 5.15, 5.16).
- INDOCIN (indomethacin) Capsules, Oral Suspension, and Suppositories — Full Prescribing Information. Revised 2019. accessdata.fda.govSource for suppository and oral suspension data; documents comparable upper GI adverse effects between suppositories and capsules, with higher lower GI effects from suppositories.
- INDOCIN SR (indomethacin extended-release capsules) — Full Prescribing Information. Revised 2019. accessdata.fda.govSource for SR formulation data: 75 mg once or twice daily; substitutes for IR in all indications except acute gout.
- Elmunzer BJ, Scheiman JM, Lehman GA, et al. A randomized trial of rectal indomethacin to prevent post-ERCP pancreatitis. N Engl J Med. 2012;366(15):1414–1422. doi:10.1056/NEJMoa1111103Landmark RCT demonstrating rectal indomethacin 100 mg reduces post-ERCP pancreatitis in high-risk patients (NNT=13); basis for guideline recommendations.
- Bhala N, Emberson J, Merhi A, et al. (CNT Collaboration). Vascular and upper gastrointestinal effects of non-steroidal anti-inflammatory drugs. Lancet. 2013;382(9894):769–779. doi:10.1016/S0140-6736(13)60900-9CNT meta-analysis: provides NSAID-class CV and GI risk estimates applicable to indomethacin.
- FitzGerald JD, Dalbeth N, Mikuls T, et al. 2020 American College of Rheumatology guideline for management of gout. Arthritis Care Res. 2020;72(6):744–760. doi:10.1002/acr.24180ACR gout guideline conditionally recommending NSAIDs (including indomethacin) for acute gout flares as first-line; full-dose initiation emphasised.
- Dumonceau JM, Kapral C, Aabakken L, et al. ESGE Guideline: prophylaxis of post-ERCP pancreatitis. Endoscopy. 2020;52(11):948–980. doi:10.1055/a-1262-3543ESGE strongly recommends routine rectal indomethacin (or diclofenac) for all patients undergoing ERCP.
- Kolasinski SL, Neogi T, Hochberg MC, et al. 2019 American College of Rheumatology/Arthritis Foundation guideline for the management of osteoarthritis. Arthritis Care Res. 2020;72(2):149–162. doi:10.1002/acr.24131Conditionally recommends oral NSAIDs for OA; indomethacin generally not first-line due to higher adverse effect profile.
- Vane JR. Inhibition of prostaglandin synthesis as a mechanism of action for aspirin-like drugs. Nat New Biol. 1971;231(25):232–235. doi:10.1038/newbio231232a0Nobel Prize-winning work establishing prostaglandin synthesis inhibition as the mechanism of NSAIDs; indomethacin was a key experimental agent.
- Indomethacin. In: LiverTox: Clinical and Research Information on Drug-Induced Liver Injury. Bethesda, MD: NIDDK; Updated Aug 5, 2025. ncbi.nlm.nih.govDocuments indomethacin hepatotoxicity as rare (likelihood score C); ALT >3× ULN in <1%; fatal cases primarily in paediatric JRA patients.
- Helleberg L. Clinical pharmacokinetics of indomethacin. Clin Pharmacokinet. 1981;6(4):245–258. doi:10.2165/00003088-198106040-00001Comprehensive PK review covering absorption (~100%), protein binding (~99%), enterohepatic circulation, and variable half-life.
- Indomethacin. In: StatPearls. Treasure Island, FL: StatPearls Publishing; Updated May 28, 2024. ncbi.nlm.nih.govComprehensive clinical review covering indications (including PDA), dosing, PK, and adverse effects; notes elimination half-life variability (1.5–16 h) due to enterohepatic circulation.
- Pacifici GM. Clinical pharmacology of indomethacin in preterm infants: implications in patent ductus arteriosus closure. Paediatr Drugs. 2013;15(5):363–376. doi:10.1007/s40272-013-0031-7PK review of IV indomethacin in neonates for PDA closure; documents age-dependent variability in clearance and half-life.