It has long been known that blood pressure typically climbs most rapidly after you get up in the morning, levels off during the middle or late part of the day, and then drops to its lowest level when you go to sleep. Now, according to a 24-patient study published in the January edition of the American Journal of Hypertension, it may be that different blood pressure drugs exert their most powerful effect at different times of the day, regardless of when they are taken.
Australian researchers evaluated the following drugs: a diuretic (hydrochloro-thiazide), a beta-blocker (atenolol), an angiotensin-converting-enzyme (ACE) inhibitor (perindopril), and a calcium-channel blocker (felodipine). The study found that the calcium-channel blocker and the diuretic tended to lower blood pressure at all hours, the beta-blocker appeared to work only during the day, and the ACE inhibitor exerted its greatest effect at night.
Much more work needs to be done, but there may be good reason to switch from high-dose monotherapy to a regimen that includes lower doses of different drugs, each of which is most effective at lowering blood pressure at different times of the day.