The Effect of Hyoscine-N-Butylbromide on Respiratory Sinus Arrhythmia in Healthy Young Subjects

Background and

Fluctuations in the heart rate can be affected by many factors such as breathing. The amplitude of heart rate variability during inhalation and exhalation provides a quantitative measure that puts the estimate of cardiac vagal function which is considered. The aim of this study was to investigate the effect of a single dose of hyoscine-N-butylbromide (hyoscine) on the amplitude of heart rate variability, namely cardiac vagal activity.

15 healthy young male subjects participated in the study. Each subject came to the laboratory twice with one week interval. Before and one hour after intramuscular injection of hyoscine or placebo, normal and deep breathing tests were performed every 10 minutes. The amplitude of respiratory sinus arrhythmia (RSA) associated with cardiac vagal activity between periods before and after administration of the drug/ or placebo were analyzed by RM_ANOVA.

Comparing with normal breathing, deep breathing increases the amplitude of the RSA. The One way ANOVA of RSA showed that hyoscine reduced the RSA amplitude that at 50 min after injection returned to basal level. Similar results were also observed during normal breathing test except that RSA amplitude at 40 min after injection of hyoscine returned to baseline.

Overall, the findings of this study showed that intramuscular injection of 20 mghyoscine reduces cardiac vagal activity that returned to base line 40-50 minutes after the injection.