Indomethacin is a powerful anti-inflammatory drug that reduces pain, swelling, and fever by blocking the production of prostaglandins, chemicals your body makes in response to injury or illness. It belongs to the class of nonsteroidal anti-inflammatory drugs (NSAIDs) and is stronger than over-the-counter options like ibuprofen or naproxen. It’s most commonly prescribed for gout flares, certain types of arthritis, and acute shoulder pain from bursitis or tendinitis.
How Indomethacin Works in the Body
When tissue is damaged or irritated, your body releases a fatty acid called arachidonic acid. An enzyme called cyclooxygenase (COX) converts that acid into prostaglandins, which trigger inflammation, pain, and fever. Indomethacin blocks both forms of this enzyme, COX-1 and COX-2, which shuts down prostaglandin production at the source.
What makes indomethacin distinctive is the way it binds to the COX enzyme. It’s classified as a “slow, tight-binding” inhibitor, meaning it latches onto the enzyme gradually but holds on firmly once it does. This gives it a potent and sustained anti-inflammatory effect compared to milder NSAIDs. After a single oral dose, the drug reaches peak levels in your blood in about two hours and has a half-life of roughly 4.5 hours, so its effects taper over the course of several hours.
Conditions It Treats
Indomethacin is FDA-approved for five conditions:
- Rheumatoid arthritis, including acute flares of chronic disease
- Ankylosing spondylitis (inflammatory arthritis of the spine)
- Osteoarthritis
- Acute painful shoulder from bursitis or tendinitis
- Acute gouty arthritis
Of these, gout is one of the most common reasons it’s prescribed. Gout flares involve intense, rapid-onset joint inflammation, and indomethacin’s strong prostaglandin-blocking action can bring relief faster than weaker anti-inflammatories. For shoulder bursitis and tendinitis, a typical course lasts 7 to 14 days, and the drug is stopped once inflammation is under control.
Use in Newborns
Indomethacin also has a specialized use in premature infants. Some babies are born with a blood vessel near the heart, the ductus arteriosus, that fails to close on its own after birth. Indomethacin given intravenously causes that vessel to constrict and close, often avoiding the need for surgery. This works precisely because prostaglandins are what keep the vessel open, so blocking their production allows it to shut.
Typical Dosing Patterns
Dosing depends on the condition. For arthritis (rheumatoid, osteoarthritis, or ankylosing spondylitis), the starting dose is usually 25 mg taken two or three times daily, with gradual increases over weeks if needed. The daily maximum is 200 mg. People with significant morning stiffness or nighttime pain sometimes take a larger portion of the day’s dose at bedtime.
For acute gout, the dose is higher from the start: 50 mg three times a day until the pain becomes tolerable, then rapidly tapered off. The goal is short, aggressive treatment rather than long-term use. For shoulder bursitis or tendinitis, the range is 75 to 150 mg daily split into three or four doses.
Indomethacin comes in oral capsules (immediate-release and extended-release) and rectal suppositories, which can be useful when nausea makes swallowing a pill difficult. The injectable form is reserved for newborns with patent ductus arteriosus.
Common Side Effects
The most frequent side effects are gastrointestinal. Nausea, indigestion, heartburn, diarrhea, and abdominal pain each occur in roughly 3 to 9 percent of people taking the drug. Constipation, bloating, and loss of appetite are also common. Headache is another well-known complaint, sometimes significant enough that people stop taking it.
More serious GI problems are less common but real. Upper GI ulcers, significant bleeding, or perforation occur in about 1 percent of people who take NSAIDs for three to six months, rising to 2 to 4 percent after a year of use. These events can happen without warning symptoms, which is one reason indomethacin is generally prescribed at the lowest effective dose for the shortest possible time.
Kidney-related effects, including fluid retention, blood in the urine, and elevated kidney function markers, are uncommon but more likely in people who are already dehydrated, elderly, or taking blood pressure medications. In rare cases, indomethacin can cause significant kidney impairment.
Cardiovascular Risks
Like all NSAIDs, indomethacin carries an increased risk of serious cardiovascular events, including heart attack and stroke. This risk can appear within the first weeks of treatment and tends to increase at higher doses and with longer use. A large meta-analysis of clinical trials found that both COX-2 selective and nonselective NSAIDs roughly doubled the rate of hospitalization for heart failure compared to placebo.
Indomethacin can also raise blood pressure or reduce the effectiveness of blood pressure medications, particularly diuretics. If you already have high blood pressure, your doctor will likely want to monitor it closely while you’re on the drug. People who have had a recent heart attack or who have severe heart failure are generally advised to avoid it unless no better option exists.
The drug is strictly contraindicated after coronary artery bypass graft surgery due to the elevated clot risk in that setting.
Who Should Not Take It
Beyond the CABG restriction, indomethacin is off-limits if you’ve ever had an allergic reaction to it, to aspirin, or to another NSAID. This includes people who developed asthma, hives, or swelling after taking those drugs. Severe, sometimes fatal allergic reactions have occurred in this group.
Because of its GI and cardiovascular risks, indomethacin is generally not a first choice for mild pain or conditions that respond to gentler options. It’s best suited for situations where strong anti-inflammatory action is specifically needed, like a gout flare, and for the shortest course that gets the job done.