This study investigated whether taking a drug to reduce high blood pressure at bedtime is more effective than taking the drug in the morning. 

High blood pressure (hypertension) occurs when blood pressure inside the body’s arteries is too high. This can put strain on the heart and damage blood vessels while also increasing the risk of blood clots.

Blood pressure measurements are given as two numbers. The first number represents the pressure inside arteries when the heart is beating (systolic blood pressure), and the second number represents the pressure inside arteries when the heart is relaxed (diastolic blood pressure). Normal blood pressure is considered to be around 120/80 mmHg.

Blood pressure can be measured at one sitting during the day (called office blood pressure) or at regular intervals for 24 hours (called ambulatory blood pressure).

Hypertension is treated with antihypertensive drugs. These include angiotensin receptor blockers (ARBs) such as valsartan (Diovan), angiotensin-converting enzyme (ACE)-inhibitors like Lisinopril (Zestril), and thiazide diuretics such as Hydrochlorothiazide (Microzide).

This study investigated whether antihypertensive drugs have different effects depending on whether they are given in the morning or night.

A total of 1,093 patients with high blood pressure and who were at risk of having a cardiovascular event (such as a heart attack) due to hypertension were included in the study. The patients received either valsartan or lisinopril for 26 weeks. Valsartan was given either in the morning or night whereas lisinopril, which stays working in the body for much longer, was only given in the morning.

Patients started on a low dose of valsartan (160 mg) and lisinopril (20 mg) for 4 weeks. This was then increased to 320 mg valsartan and 40 mg lisinopril for 8 weeks. If blood pressure was still too high after this (e.g. office blood pressure > 140/90 mmHg), hydrochlorothiazide (12.5 mg) was added for the remaining 14 weeks.

The study found that valsartan and lisinopril had similar effects on ambulatory blood pressure between weeks 12 and 26, even though lisinopril was only given in the morning and valsartan was given either in the morning or night time. Valsartan had the same effect on blood pressure, regardless of it being given in the morning or night.

Valsartan given in the morning reduced blood pressure by 13.3 mmHg by 26 weeks, night time valsartan reduced blood pressure by 12.3 mmHg and lisinopril given in the morning reduced blood pressure by 13.7 mmHg.

The study concluded that valsartan (320 mg) in the morning or night has the same effect on blood pressure.

One limitation of the study is that the investigators were not able to precisely determine the time each patient went to bed and when they awoke, and if their treatment times were consistent throughout the study. 

If you or someone you know have high blood pressure, talk to a doctor about whether taking your antihypertensive medication at a specific time during the day is beneficial.