FRIDAY, Nov. 18, 2016 (HealthDay News) -- Cigarette smoking may decrease the effectiveness of drugs taken during early stages of chronic kidney disease, a small study suggests.

Blood pressure-lowering drugs known as angiotensin-converting enzyme inhibitors slow kidney decline by relaxing blood vessels.

"It has practically become dogma that if you have a patient with high blood pressure and chronic kidney disease that you start them on an angiotensin-converting enzyme inhibitor," said study author Dr. Bethany Roehm, of Tufts Medical Center in Boston.

"We are often comforted as clinicians that we are doing something to help slow progression of their kidney disease in doing this," Roehm added in a news release from the American Society of Nephrology.

"But our data suggest that this may not be the case for smokers, and our study underscores the importance of doing all we can as clinicians to encourage our patients to stop smoking," she noted.

Roehm and her colleagues tracked 108 smokers and 108 nonsmokers taking angiotensin-converting enzyme inhibitors for early chronic kidney diseases. Researchers enrolled all the smokers in a quit-smoking program, and 25 quit.

The study participants were tracked for five years. Kidney function worsened faster in smokers compared to nonsmokers and those who quit. Smokers also showed signs that the drugs weren't protecting their kidneys as well, possibly because cigarette smoking caused oxidative stress, the researchers pointed out.

However, Roehm cautioned that the findings need to be confirmed in larger studies.

The research was presented Thursday at an American Society of Nephrology conference in Chicago. Studies released at meetings should be considered preliminary until they're published in a peer-reviewed medical journal.

More information

For more about kidney disease and smoking, see the National Kidney Foundation.