Doctors may no longer need trial-and-error when prescribing blood pressure drugs. A huge new study has mapped exactly how much each medication, alone or in combos, lowers blood pressure, and offers doctors an online tool to guide treatment.
There are lots of different medications available to treat high blood pressure, or hypertension, which can make choosing the right one tricky. Until now, it’s been a case of trial and error in finding the most effective drug. That might be a thing of the past thanks to a new, recently published study.
Led by researchers from the University of New South Wales’ (UNSW) George Institute for Global Health in Australia, the study sought to figure out exactly how much commonly used medications lowered blood pressure (BP), both when used alone and when combined with other antihypertensives. They also looked at whether taking a bigger dose actually made a difference, and how starting BP affected the results.
“This is really important because every 1 mmHg [millimeter of mercury] reduction in systolic blood pressure lowers your risk of heart attack or stroke by 2%,” said Nelson Wang, MD, PhD, cardiologist and research fellow at the George Institute, and the study’s lead author. “But with dozens of drugs, multiple doses per drug, and most patients needing two or more drugs, there are literally thousands of possible options, and no easy way to work out how effective they are.”
A healthy blood pressure is generally considered to be below 120/80 mmHg. The top number (systolic pressure) is the pressure in the arteries when the heart is contracting; the bottom number (diastolic pressure) is when the heart is resting between beats.
For this study, the researchers pooled the data from 484 randomized clinical trials with more than 100,000 people. All trials had been carefully controlled, comparing a drug (or a drug combination) to a placebo. They looked at the five main types of antihypertensives: angiotensin-converting enzyme (ACE) inhibitors, angiotensin II receptor blockers (ARBs), beta-blockers, calcium channel blockers, and diuretics.
- Angiotensin converting enzyme (ACE) inhibitors: Stop the body from making a hormone that tightens blood vessels, so the vessels relax and BP goes down.
- Angiotensin II receptor blockers (ARBs): Block the action of the same hormone, keeping blood vessels from tightening and helping them stay relaxed.
- Beta-blockers: Slow the heart rate and reduce how hard the heart pumps, lowering blood pressure.
- Calcium channel blockers: Prevent calcium from entering the muscle cells of the heart and blood vessels, so the vessels relax and widen.
- Diuretics (“water pills”): Help the body offload extra salt and water through the urine, reducing the amount of fluid in the blood vessels and lowering pressure.
The average participant started with a blood pressure of about 154/100 mmHg, and the researchers looked mainly at effects on systolic blood pressure. They found that taking one medication at a standard dose lowered BP by about 9 mmHg on average. Doubling the dose resulted in an additional drop of about 1.5 mmHg. This means that higher doses do work, but the extra benefit is small. Taking two drugs together at the standard dose lowered BP by about 15 mmHg, noticeably better than one drug alone. Doubling the doses of both drugs resulted in an additional approximately 2.5 mmHg drop.
People who began with lower BP saw smaller benefits from the drugs. For every 10-mmHg lower starting point, the drop achieved was about 1 mmHg less. Most single drugs (about 80%) were found to be “low-intensity,” meaning the BP drop was less than 10 mmHg. Most two-drug combinations were “moderate-intensity” (10-19 mmHg drop). Only about one in 10 combinations produced a “high-intensity” drop of 20 mmHg or more.
That wasn’t the end of the study, though. The researchers took this data and built a model that could predict how these drugs, either alone or in combination, would affect a patient’s BP. The resulting Blood Pressure Treatment Efficacy Calculator showed a high correlation between predicted and observed systolic BPs when validated on external trials; that is, it showed strong accuracy when it was tested. The calculator is now available for online use.
“Using the calculator challenges the traditional ‘start low, go slow, measure and judge’ approach to treatment, which comes with the high probability of being misled by BP readings, inertia setting in or the burden on patients being too much,” said the study’s corresponding author, Anthony Rodgers, PhD, Professor of Global Health at UNSW Sydney’s Faculty of Medicine and Chair of Clinical Epidemiology at the Faculty of Medicine at the Imperial College of London. “With this new method you specify how much you need to lower blood pressure, choose an ideal treatment plan to achieve that based on the evidence, and get the patient started on that ideally sooner rather than later.”
The researchers plan to test the new approach in a clinical trial, where, guided by the calculator, patients will be prescribed treatments based on the amount needed to lower their blood pressure.
“Given the enormous scale of this challenge, even modest improvements [in blood pressure] will have a large public health impact – increasing the percentage of people whose hypertension is under control globally to just 50% could save many millions of lives,” Rodgers said.
The study was published in the journal The Lancet.
