How long it takes for antihypertensive drugs to take effect depends on which antihypertensive drugs are chosen, short-acting preparations take effect within 30min, medium-acting preparations take effect within 60min, and long-acting preparations take effect within 24h. 1. Short-acting antihypertensive drugs, such as nifedipine tablets, are often used to lower blood pressure quickly when blood pressure increases. It often takes effect within 30min after taking the drug, because of its fast onset of action to lower blood pressure is not stable, so when using this kind of drugs to lower blood pressure need to always observe the changes in blood pressure. 2. Medium-acting antihypertensive drugs: such as Nitrendipine, oral intake of such drugs within 60min to start the effect, but to play the maximum antihypertensive effect often need 5~6 hours, and then the effect of antihypertensive gradually weakened. 3. Long-acting antihypertensive drugs: such as Irbesartan tablets, these drugs have a slow onset of action, but the most stable antihypertensive effect. Its onset of action is often within 24 hours after taking the drug, the amount of drugs accumulated to a certain extent to play the maximum antihypertensive effect, the time required is often 3 to 4 days or even up to a week. Selection of appropriate antihypertensive drugs, should go to a regular hospital for consultation and treatment.