Dave FL how long did it take for Losartan to lower your BP? I've been taking 100 MG for a week now and my BP can still go to 163/100! My doctor took me off Clonidine 0.2 MG Twice a day and put me on the Losartan. I think he took me off the clonidine too quickly. Only weaned me off it for 3 days. Since then my BP has spiked.