Pharmacology · Nonsteroidal anti-inflammatory drugs (NSAIDs)

Indometacin !

A potent non-selective NSAID used for acute gout and to close the ductus arteriosus in premature babies; headache and other central effects are common.

Updated 2026-11-01

Class: Nonsteroidal anti-inflammatory drugs (NSAIDs)
Enzyme: Cyclooxygenase 1 and 2 (COX-1/COX-2)
ATC code: M01AB01
WHO Model List of Essential Medicines

Also called: indomethacin

Cyclooxygenase 1 and 2 (COX-1/COX-2)Indometacin

The figure shows indometacin in the channel of mouse COX-2, which keeps the same site as the human enzyme.

Target in 3D: Cyclooxygenase 1 and 2 (COX-1/COX-2). PDB structure 4COX (RCSB PDB, public domain). View the structure at RCSB PDB

Mechanism of action

Indometacin, an indole derivative, is a potent non-selective cyclooxygenase inhibitor. It occupies the channel through which arachidonic acid enters and blocks the synthesis of the prostaglandins that drive inflammation, pain and fever. Because prostaglandins keep the ductus arteriosus open, inhibiting them in the premature newborn helps the ductus close.

Occupies the channel of COX-1 and COX-2
Arachidonic acid is not turned into prostaglandin H2
Fewer prostaglandins: less inflammation, pain and fever
In the premature baby, without prostaglandins the ductus closes

Pharmacokinetics

Absorption: Almost complete oral bioavailability.
Distribution: Highly bound to plasma proteins.
Metabolism: Liver: demethylation, debenzoylation and glucuronidation; it undergoes enterohepatic cycling.
Elimination: Urine (most) and faeces.
Half-life: About 4.5 hours on average.

Indications

Acute gouty arthritis Gout →
Moderate to severe rheumatoid arthritis Rheumatoid arthritis →
Ankylosing spondylitis Ankylosing spondylitis →
Moderate to severe osteoarthritis Knee Osteoarthritis →
Closure of a haemodynamically significant patent ductus arteriosus in premature infants (intravenous) Patent ductus arteriosus →

Adverse effects

Common

Headache
Dizziness
Dyspepsia and nausea
Abdominal pain and diarrhoea

Contraindications

Hypersensitivity to the drug
Asthma, urticaria or another allergic reaction after acetylsalicylic acid or another NSAID
The setting of coronary artery bypass graft (CABG) surgery
In neonates: untreated infection, active bleeding (above all intracranial or gastrointestinal), thrombocytopenia or coagulopathy, necrotising enterocolitis, markedly impaired kidney function
In neonates with congenital heart disease that depends on an open ductus (pulmonary atresia, severe tetralogy of Fallot, severe coarctation)

Key interactions

Triamterene: Reversible acute renal failure has been reported; they are not given together.
Diflunisal: Raises indometacin levels and the risk of gastrointestinal bleeding.
Lithium: Raise its blood levels by lowering renal clearance.
Digoxin: May raise its concentration and prolong its half-life.
ACE inhibitors, ARBs and diuretics: Blunt their antihypertensive and diuretic effect; in older or volume-depleted patients they can precipitate acute kidney injury.

What is monitored

Gastrointestinal symptoms and signs of bleeding
Kidney function and potassium
Blood pressure
Persistent headache, mood or vision changes
In the premature baby: urine output, creatinine, electrolytes and signs of bleeding

Administration and safety

Oral forms are given with food, right after meals or with antacids.
The intravenous form is for the premature ductus; it is used in neonatal units with monitoring of urine output and bleeding.

Nursing care

Before starting: history of ulcer, bleeding, kidney or cardiovascular disease, or asthma with NSAIDs.
Watch for black stools, vomiting blood, abdominal pain and signs of anaemia.
Watch blood pressure, oedema, urine output and creatinine, above all in older patients or those on diuretics.
Ask about headache, dizziness or mood changes: central effects are common with this NSAID.
In the premature baby, measure urine output and watch for gastrointestinal or intracranial bleeding.

Pregnancy and breastfeeding

From about week 20 it can cause fetal kidney dysfunction with oligohydramnios, and from about week 30 premature closure of the ductus arteriosus; so use is limited between those weeks and avoided late in pregnancy.

Test yourself

Think of the answer, then tap the question to see it.

Why does indometacin close the ductus arteriosus in a premature baby?

Prostaglandins keep the ductus open; by inhibiting the cyclooxygenases, indometacin lowers prostaglandins and the ductus closes.

In which newborn is closing the ductus with indometacin contraindicated?

One with congenital heart disease whose pulmonary or systemic flow depends on the open ductus, such as pulmonary atresia or severe tetralogy of Fallot.

Which common adverse effect sets indometacin apart from other NSAIDs?

Headache; it also causes dizziness and can worsen depression, epilepsy and parkinsonism.

Which diuretic is not combined with indometacin, and why?

Triamterene, because the combination caused acute renal failure.

Add to my cards (4)

← Back to the class: Nonsteroidal anti-inflammatory drugs (NSAIDs)

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: Indomethacin: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); INDOMETHACIN capsule (DailyMed (U.S. National Library of Medicine), 2026); INDOMETHACIN injection, powder, lyophilized, for solution (DailyMed (U.S. National Library of Medicine), 2026); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 42 (McGraw Hill, 2023).

Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake

Representative model, for educational purposes only.