Wednesday, July 20, 2011

Heart drugs best taken at bed time, says researcher

Medications for heart patients may do a better job if they are taken at night, just before bed time, according to a researcher in Canada. “Heart drugs are often given to patients in the morning for convenience, without considering biological rhythms or time-related risks of adverse effects,” said Professor Tami Martino from the department of biomedical sciences at the University of Guelph, Ontario, Canada. However, it is better if such drugs are given at bed time, she added, because they are better able to counter the peaking actions of the renin-angiotensin-aldosterone system (RAAS) which is associated with cardiac remodeling. Martino was the lead author of a study which showed that the short-acting ACE inhibitor captopril improved cardiac function and structure in hypertensive mice when given at sleep time, versus placebo or captopril when given during wake time. [J Am Coll Cardiol 2011;57(20):2020-2028] “The sleep-time benefit of giving the ACE inhibitor correlates with the biological rhythm of this hormone,” she said. “By targeting those hormones when they’re highest during sleep, you’re dropping their levels so they’re not doing so much damage.” In the study, mice were administered intraperitoneal captopril 15 mg/kg or placebo at either murine sleep time or wake time for a period of 8 weeks, starting 1 week after surgery to induce cardiovascular pressure overload by transverse aortic constriction. The results also suggest that physicians might consider using a short-acting version of the drug, said Martino. “Since the drug is most effective during sleep hours, it’s not necessary to have its effects last throughout the entire day. Using a short-acting version of the drug may help to reduce its side effects.” It has long been known that diurnal variations exist for the functioning of the human body, and that biological and physiological rhythms play an important role in health and disease. “RAAS is an important pathway in the pathogenesis of cardiac remodelling and hypertrophy,” said Dr. Tang Hak Chiaw, a consultant with the department of cardiology at the National Heart Centre, Singapore. “By targeting the pathway at the time when it is most active, the authors have successfully shown differences in the treatment outcome in an animal model. This paves the way for clinical studies in human subjects.” However, Chiaw said it would be too premature to advise patients when to take their medication based on this study alone. “In our current practice, clinicians would usually choose a medication that has a longer duration of action to give 24-hour coverage [or] protection if there is an option. Of course, this study [will] generate interest and, as the authors have appropriately concluded, their findings will “provide new opportunities for the effective treatment of cardiovascular disease.” – GT

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