Warfarin + amiodarone — ↑ anticoagulation
- Amiodarone inhibits warfarin metabolism
- mainly CYP2C9; also 3A4/2C19
- INR rises slowly over days–weeks
- Effect persists because amiodarone t½ is long
- Often need ~25–50% warfarin reduction
- Check INR frequently after start/stop
Interaction at a glance
- INR rises slowly over days–weeks
- Often need ~25–50% warfarin reduction
Timing / washout
- Amiodarone inhibits warfarin metabolism
- mainly CYP2C9; also 3A4/2C19
- INR rises slowly over days–weeks
Management
- Often need ~25–50% warfarin reduction
Monitoring
- Effect persists because amiodarone t½ is long
- Check INR frequently after start/stop
Self-check
- About how much warfarin reduction is often needed after starting amiodarone?
About 25–50%.
- How quickly does the warfarin–amiodarone interaction develop?
Gradually over days to weeks.
- What should be monitored after starting or stopping amiodarone with warfarin?
INR.
Drugs in this interaction (2)
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