Indomethacin is a potent non-steroidal anti-inflammatory drug (NSAID) of the arylacetic acid class. It is a non-selective inhibitor of cyclooxygenase (COX-1 and COX-2) enzymes, leading to potent anti-inflammatory, analgesic, and antipyretic effects. The 75mg strength is typically formulated as a sustained-release (SR) or modified-release capsule, designed for once-daily administration in conditions requiring prolonged symptom control, such as osteoarthritis, rheumatoid arthritis, and ankylosing spondylitis. It is considered one of the most potent traditional NSAIDs.
Adult: For chronic conditions (RA, OA, AS): 75mg sustained-release capsule once daily, usually in the morning or at bedtime. May initiate with 25mg immediate release 2-3 times daily and switch to 75mg SR for maintenance. Maximum daily dose: 150-200mg.
Note: Take the 75mg SR capsule whole with a full glass of water, preferably with food or milk to minimize gastric upset. Do not crush, chew, or open the capsule. Swallow it intact. Bedtime administration may help control morning stiffness.
Indomethacin exerts its therapeutic effects by non-selectively inhibiting the enzyme cyclooxygenase (COX), both COX-1 and COX-2 isoforms. COX catalyzes the conversion of arachidonic acid to prostaglandin G2 and then to prostaglandin H2, the precursor for various prostanoids (prostaglandins, prostacyclin, thromboxane). By inhibiting prostaglandin synthesis, it reduces inflammation, pain, and fever. COX-1 inhibition is responsible for many adverse effects (GI, renal), while COX-2 inhibition mediates anti-inflammatory effects.
Pregnancy: Category C (first and second trimester). Avoid in third trimester (Category D) due to risk of premature closure of ductus arteriosus, oligohydramnios, and prolonged labor. Use only if potential benefit justifies fetal risk.
Driving: May cause dizziness, drowsiness, or blurred vision. Patients should not drive or operate machinery until they know how the drug affects them.
| Warfarin, Acenocoumarol | Increased risk of bleeding due to antiplatelet effect and protein binding displacement. | Major |
| Aspirin (low-dose) | Competitive COX inhibition; may reduce indomethacin efficacy and increase GI toxicity. | Moderate |
| Lithium | Decreased renal clearance of lithium, leading to toxicity (tremor, confusion). | Major |
| Methotrexate | Decreased renal clearance of methotrexate, increasing risk of bone marrow suppression. | Major |
| Diuretics (Furosemide, Thiazides) | Reduced diuretic and antihypertensive efficacy; risk of renal impairment. | Moderate |
| ACE Inhibitors (Ramipril, Enalapril) / ARBs (Losartan) | Reduced antihypertensive effect; increased risk of renal impairment and hyperkalemia. | Moderate |
| Corticosteroids (Prednisolone) | Synergistic increase in risk of GI ulceration and bleeding. | Major |
| SSRIs (Fluoxetine, Sertraline) | Increased risk of upper GI bleeding. | Moderate |
| Cyclosporine | Increased risk of nephrotoxicity. | Major |
| Antiplatelets (Clopidogrel) | Additive risk of GI bleeding. | Moderate |
Same composition (Indomethacin (75mg)), different brands: