ScienceDaily (May 9, 2011) — When doctors give heart drugs to patients, the time of day can make a big difference, according to new research by University of Guelph scientists. Many doctors prefer to give heart drugs to patients in the morning. But the study revealed that angiotensin-converting enzyme (ACE) inhibitors -- commonly given to patients with high blood pressure or after a heart attack or during heart failure -- improve heart structure and function when given at sleep time. In fact, when administered during wake time, ACE inhibitors are no more effective than a placebo, the study found.