Improving blood pressure control through night-time medication
Administration of a long-acting medication at the time that is most suitable for maximum patient compliance is the best approach in controlling blood pressure, said Dr Trefor Morgan at the recently concluded 13th Asian-Pacific Congress of Hypertension (APCH 2017), held at the Suntec Singapore Convention and Exhibition Centre.
If blood pressure control for 24 hours is not certain, then night-time medication may have an advantage over daytime medication, he added. What is important is that it should be “ensure[d], either by measuring it or by knowing what the drugs do, that sleep and awaking blood pressure is controlled.”
Citing various reports from the literature, Dr Morgan established a strong correlative link between the declining blood pressure during sleep and various cardiovascular outcomes such as ischaemic stroke, with lower sleep blood pressures predicting better outcomes.
Blood pressure while waking up, on the other hand, is a weak predictor of cardiovascular events despite being the period where such events normally occur.
These daily fluctuations in blood pressure may be principally explained through the changes in the activity of different control systems, Dr Morgan explained. At night, during sleep, the sympathetic nervous system relaxes, resulting in the decline in blood pressure which, in turn, causes the renin-angiotensin system to kick in.
It is important to note that these trends do not mean that the renin-angiotensin system is normally turned off, he emphasized, stating that renin levels also fluctuate with activity and posture during the day.
Moreover, because these changes in the activity of the control systems are not universal, they also account for the interindividual differences in the daily blood pressure fluctuations.
Indeed, many studies group participants into two: the dippers who show the normal decline in blood pressure during sleep and the nondippers who do not show this night-time fall in blood pressure.
Notably, nondippers have been shown, across many studies, to have poorer prognosis than dippers, and thus benefit the most from pharmaceutical interventions.
However, “if we have these two important systems controlling blood pressure with different activities, if we’re using drugs that interfere with the activity of this system, we need to make certain the drug is present at the time when the system is active,” said Dr Morgan.
This makes the timing of medication critical because the duration of the drug in the body is highly dependent on its dose, and it is highly unusual that drugs work for 24 hours.
It is routine clinical practice to administer medication in the morning and measure its effects a couple of hours after. In this setup, the peak and adequate blood pressure response is achieved during the day and is typically already gone by the critical periods: during sleep and as the patients wake up.
So, to improve blood pressure control, Dr Morgan emphasized that medications are titrated using the morning blood pressure predose measurements and administered at night. That way, “you avoid measurement at the highest peak effect.”