Verapamil, diltiazem, digoxin, amiodarone and other antiarrhythmics (risk of bradycardia/heart block), other antihypertensives (additive BP lowering), clonidine (withdrawal interaction), insulin/oral antidiabetics (masks hypoglycaemia), NSAIDs (may reduce BP control), CYP2D6 inhibitors like fluoxetine/paroxetine/quinidine (increase metoprolol levels)