How long it takes for high blood pressure to come down depends on the antihypertensive medication used and how high the patient’s blood pressure is. If intravenous antihypertensive medications are used, blood pressure will generally begin to drop within 5-10 minutes and will drop significantly within half an hour to an hour of use. If the patient is using short-acting antihypertensive drugs, the blood pressure will generally start to work within 10 minutes and will drop in 2-3 hours. If a long-acting antihypertensive drug is used, it usually starts to work in half an hour and the duration of blood pressure reduction can last for 6-8 hours. If the patient’s blood pressure is high and is Grade 3 hypertension, it takes 3-5 days to bring the blood pressure down to normal. If the patient has Grade 1 hypertension, it will take 1-2 days to bring down to normal after using antihypertensive drugs.