Updated 07 February 2018

Why taking more than one blood pressure drug is better

Researchers have found that two-thirds of patients taking a blood pressure-lowering drug don't improve as much as their doctors would like.

More than 6.2 million South Africans have blood pressure higher than 140/90mm Hg. More than 3.2 million of these have blood pressure higher than 160/95mm Hg, a level, which is unacceptably high, according to researchers.

Combining low doses of several different blood pressure drugs may be better than using a standard dose of just one medication, a new review of past studies suggests.

The review was published online in the journal Hypertension.

Ultra-low doses

Two-thirds of patients taking a blood pressure-lowering drug don't improve as much as their doctors would like, the researchers noted.

Citing a "critical need" for new approaches, they reviewed 42 studies involving ultra-low doses of multiple medications.

Their conclusion: "Low doses can achieve large effects when used in combination," said review co-author Dr Anthony Rodgers. "What we found was that four quarter doses [of different medications] gives a lot of benefit with few apparent side effects."

High blood pressure is a leading cause of stroke, heart attack and several other major conditions, so it's important to get good treatment, said Rodgers. He is a professor of global health at the George Institute for Global Health and University of New South Wales, in Australia.

However, "all blood pressure medications have only moderate effects when used alone, and many have side effects when used at higher doses," he added.

Combination doses

Cardiologist Dr Eugene Yang said blood pressure medications seem to work better when they're combined.

"There seems to be a synergetic effect between two kinds of drugs," said Yang, who wasn't involved in the study.

About one out of three US adults has high blood pressure, according to the US Centers for Disease Control and Prevention.

Blood pressure meds


In this new study, almost 20 300 adults had high blood pressure. Participants were taking different types of blood pressure medications, including ACE inhibitors, angiotensin receptor blockers, beta blockers, thiazides and calcium channel blockers.

According to the researchers, combining quarter doses of two drugs was as effective as a single standard dose of one blood pressure-lowering medication.

Even better, a combination of four medications – each at one-quarter dose – was nearly twice as effective as one drug at the standard dose, they found.

Fewer side effects

"A quarter dose gives about half as much benefit, which is not a lot by itself, but still something, with little or no side effects," Rodgers said.

In general, all of the quarter-dose combinations reduced systolic and diastolic blood pressure (the upper and lower numbers in a blood pressure reading) by several points compared to a placebo.

One study of quarter doses of four medications combined found that that combination reduced systolic blood pressure by 22 points and diastolic by 13 points, on average, compared to a placebo, the researchers reported.

Little information was provided on side effects for the four-drug combo. But side effects for the other quarter-dose therapies were far less than those seen with a standard dose of one blood pressure-lowering medication, the researchers said.

Yang pointed out that the research has limitations. Most of the studies ended more than 17 years ago, he said. He also noted that several of the authors have received funding from drug makers. Also, two of the authors, including Rodgers, are listed as inventors on patent applications related to this area of research.

Find out if you are at risk for hypertension, and just how big your risk is: Hypertension questionnaire

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Ask the Expert

Hypertension expert

Dr Jacomien de Villiers qualified as a specialist physician at the University of Pretoria in 1995. She worked at various clinics at the Department of Internal Medicine, Steve Biko Hospital, these include General Internal Medicine, Hypertension, Diabetes and Cardiology. She has run a private practice since 2001, as well as a consultant post at the Endocrine Clinic of Steve Biko Hospital.

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