Researchers discover why common blood-pressure medicine doesn’t work for some people: your kidneys don’t want to lose salt

Each year, more than 120 million prescriptions are written around the world for thiazide drugs, which lower salt to treat high blood pressure. High blood pressure affects 28 percent of Kentucky adults, according to the state Department for Public Health. Thiazide drugs often save lives but are ineffective in some patients and only work for a time in others. A study by University of Maryland School of Medicine researchers has found a key reason for the failure.

Thiazides prevent salt from moving through the kidney, causing it to expel salt and water. However, the researchers found that the kidney seems to know “that it’s losing too much salt and activates mechanisms to retain salt in other ways,” said Paul Welling, a professor of physiology at the University of Maryland.

The researchers studied an animal model designed to prevent salt retention, which imitated the thiazides’ effects. They discovered almost 400 genes that alter their activity to assist regulation of the kidney’s salt control. Eventually, it might be possible to make drugs that affect the body’s mechanisms that control how the body interacts with thiazides.

Welling and his colleagues also may have discovered a “biomarker” that could allow doctors to easily find out in which patients thiazides will not work. When the kidney is working against the thiazides, a certain molecule increases in the urine. “Now that we know more about these novel pathways and processes, we can begin to find new ways to help patients with high blood pressure,” said Dean E. Albert Reece, vice president for medical affairs at the University of Maryland.