Answer
Starting siponimod fumaric acid while taking verapamil or diltiazem can add to their heart-rate-lowering effects, potentially causing severe bradycardia and heart block, so initiation is generally not recommended unless anticipated benefits outweigh risks.
Sources for this answer
- Mayzent 0.25 mg, 1 mg & 2 mg film-coated tabletsNovartis Pharmaceuticals UK Ltd · emc · SmPC §4.4 Special warnings and precautions for use · Version 8Document updated
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