The greatest risk is when several different types of the drugs, known as antihypertensives, are taken in combination, and, in particular, the drugs that regulate the hormone, renin, which affects blood pressure levels.
Researchers from the University of Virginia school of medicine have noticed damage to the kidneys when both drugs are taken in tests with laboratory mice. They're not sure if they would see the same problem in humans.
Renin has a dual function; it doesn't only regulate blood pressure, it also helps create blood vessels when we're developing in the womb. When the drugs block renin production, they also seem to trigger another process that damages the kidneys. "It was as though the renin cells were trying to build blood vessels, only these were defective and non-functional," said R Ariel Gomez, one of the researchers.
Their discovery makes sense: pregnant women are not permitted to take drugs that suppress renin production for that very reason.
The discovery doesn't mean that people should instantly stop taking the medication, but it does throw into question the continued use of combination drugs, and just how low—and fast—blood pressure levels need to be reduced.
Until the problem is seen in humans, doctors should be a little conservative, and not look to treat high blood pressure quite so aggressively, Gomez added.