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