Cardiac autonomic modulation during methadone therapy among heroin users: A pilot study

► We investigate heroin users treated by methadone and healthy controls. ► We compare heart rate variability before and 1 h after methadone use. ► Heroin users show decreased cardiac vagal activity than controls. ► Heroin users with lapse show an increase in high-frequency component. ► Methadone therapy facilitates vagal regulation in patients with a recent lapse.