Major
Prednisolone × Warfarin
Glucocorticoids×Vitamin K antagonist anticoagulants
Mechanism
Prednisolone (a systemic glucocorticoid) raises fibrinogen and clotting factors but can also alter warfarin metabolism through liver enzymes. The effect is unpredictable: INR may either drop or rise.
Symptoms
If INR drops: thromboembolic risk (deep vein thrombosis, stroke in atrial fibrillation). If INR rises: gum bleeding, epistaxis, bruising, GI bleeding (amplified by glucocorticoid-induced gastric mucosa injury).
Management
When prednisolone starts, is escalated, or is withdrawn, check INR at 1 week, then every 2 weeks until stable. Titrate warfarin to INR. PPI cover with pantoprazole is mandatory.