Again it depend regarding which drug you are talking !!But generally it is best to take in morning hours as during the day many psychosomatic works are going on and on we need to have our blood pressure to control !As in evening hours our thinking and prime important things are not causing much worries we can have a cool effect in night time so we do not need the availability of anti hypertensive drug to the extent we need in beginning of the day !But some anti hypertensive drug is also having heart protective effect separately and that can be taken for both the purpose in evening hours !Always YouRsmE