Calcium channel blockers (verapamil, diltiazem), antiarrhythmics (amiodarone), digoxin, clonidine (rebound hypertension on withdrawal), other antihypertensives, insulin/oral antidiabetics (masks hypoglycaemia), NSAIDs (may reduce antihypertensive effect), bronchodilators (opposing effects), antidepressants like fluoxetine/paroxetine (may increase levels), cimetidine (increases levels), rifampicin (decreases levels)