As the coronavirus pandemic rages on, medical experts are debating whether blood pressure-lowering drugs that are taken by many millions of people worldwide might make COVID-19 more deadly — or less so.

Several professional medical organizations have said no evidence exists to justify changing guidelines for prescribing the drugs, called angiotensin-converting enzyme inhibitors (ACEI) and angiotensin receptor blockers (ARB). The medications are mainstays of treating hypertension, heart disease, heart failure, diabetes, and chronic kidney disease.

Now, two separate reviews of existing studies — one published in the New England Journal of Medicine, the other in Mayo Clinic Proceedings — speculate that the drugs may be helpful for coronavirus patients.

The Mayo review is by physicians battling the pandemic in Italy, Spain, and the U.S. In an accompanying video, coauthor Carl J. Lavie, a cardiologist at the John Ochsner Heart and Vascular Institute in New Orleans, explained that a hormone involved in high blood pressure narrows blood vessels while increasing inflammation and tissue scarring. ARBs and ACEIs tamp down production of the hormone.

That “could actually be very beneficial for preventing lung injury and also for systemic health,” Lavie said. “Certainly, it is premature right now to start using these agents as a preventive measure for COVID-19 in patients. However, this is an active area for investigation.”

ACEIs and ARBs act on a complex system that regulates blood pressure, fluid, and mineral balance. The problem — in theory — is that the drugs increase the activity of a protective enzyme that also appears to help the coronavirus gain entry to cells in the lungs and other organs.

The concern is that the drugs could make patients more susceptible to the virus, or worsen the severity of infection. A number of studies in China, where the novel virus emerged in December, have linked high blood pressure to a higher risk of respiratory failure and death in coronavirus patients. Also, hypertension was the most common chronic health problem among COVID-19 patients.

But the studies could not answer the chicken-and-egg question: Did these coronavirus patients, who tended to be older, fare worse because of their high blood pressure or other chronic illnesses, or because of drugs they were taking to treat chronic illnesses — or both?

In the New England Journal article, Harvard Medical School cardiologist Muthiah Vaduganathan and his coauthors point out that after the coronavirus gets into cells using the enzyme, the germ appears to suppress the enzyme, thus reducing its protective effects in organs. That suggests ARBs and ACEIs, which boost the enzyme, may be beneficial. To test that idea, a clinical trial of losartan, an ARB, is now underway in Minnesota in hospitalized coronavirus patients who have not previously been treated with the blood pressure drugs.

The Mayo article concludes that one thing is clear: Patients should not stop taking ARBs and ACEIs because these drugs reduce deaths from cardiovascular disease and kidney disease.