Patients with stable heart failure who take acetazolamide, the mild diuretic and respiratory stimulant, before bedtime may significantly reduce sleep apnea and improve overnight blood oxygen levels and daytime alertness, according to an article in the January 15 issue of the American Journal of Respiratory and Critical Care Medicine.

The current research studied 12 men with stable heart failure (average age, 66 years) who had more than 15 episodes per hour each night of sleep apnea, with breathing pause at least 10 seconds in length. There were no significant patient differences in body mass index, blood pressure, or heart rate during the two phases of the study.

The study design was a double-blind, cross-over protocol with either acetazolamide or placebo taken one hour before bedtime over the course of six nights. There was a two-week washout period between the two study segments?acetazolamide and placebo.

“An important finding of the double-blind study was the significant improvement in patient perception of improved sleep quality, waking up more refreshed, with less daytime fatigue and sleepiness while taking acetazolamide, compared with placebo,” said Shahrokh Javaheri, MD, lead author of the study.

Each patient underwent a sleep test, an analysis of blood gases as well as a pH study (a test of acidity or alkalinity), a measurement of serum electrolytes, a pulmonary function test, plus other measurements at the start of the study and at the completion of each arm (acetazolamide and placebo).

“We hypothesize that with long-term drug therapy, as sleep-related breathing disorders improve, it may be reflected in an improvement in cardiac function that will further improve periodic breathing, resulting in a positive feedback cycle,” said Javaheri. “Improvement in sleep apnea may assist cardiac function by a variety of mechanisms such as improved oxygenation.”

The author points out that since the short-term efficacy of the drug has been documented, more long-term studies are needed to measure patient cardiac function, quality of life and levels of norepinephrine in the plasma and urine.