Source: Lancet  |  Posted 9 years ago

Different drug classes have variable effects on blood pressure which depend on the time of day they are taken.

Multiple drug therapy may need to be tailored accordingly, say specialists in Heidelberg, Victoria, Australia.

Response to drugs which work relatively non-specifically, such as diuretics and calcium blockers, was relatively consistent over 24 hours, say the researchers. But, response to beta blockers and to angiotensin converting enzyme inhibitors reflected the activity of control systems.

This activity, which controlled blood pressure, varied around the clock. Using drugs which selectively blocked these systems could mean that the fall in blood pressure might not be consistent throughout the 24 hours.

The specialists studied 24 patients, aged over 65 years, who had systolic blood pressure exceeding 150 mm Hg but had not been treated.

In a double-blind, crossover study with a balanced design, the patients received placebo, beta-blocker atenolol 50 mg., angiotensin converting enzyme inhibitor perindopril 8.0 mg., calcium blocker felodipine 10 mg. or diuretic hydrochlorothiazide 50 mg. for two months.

Ambulatory blood pressure was monitored at the end of each period and divided into awake periods (9:00 am to 10:00 pm), sleep periods (midnight to 6:00 am) and morning periods (6:00 to 9:00 am). Medication was taken at 9:00 am.

All four drugs lowered 24-hour mean systolic blood pressure, however, atenolol caused the smallest effect. The fall in awake blood pressure with perindopril was less than with felodipine or hydrochlorothiazide.

Atenolol caused no significant fall in sleep or morning systolic blood pressure. Falls in sleep or morning systolic blood pressure with the other three drugs were significant and greater than with atenolol. Perindopril caused a greater fall in sleep blood pressure than the other drugs.

The awake-sleep difference in systolic blood pressure increased with perindopril, stayed the same with felodipine and hydrochlorothiazide, and declined with atenolol.