To explore the extent to which 2007 Department of Health guidelines on monitoring of high-dose (⩾100 mg) methadone were followed, the reasons for non-adherence to these and the prevalence of QTc prolongation. We developed a simple tool for collecting data from case notes.

Out of 25 service users, 11 had had an electrocardiogram (ECG) and 7 had evidence of requests sent to general practitioners. After implementation of our recommendations, ten more service users had ECGs within 1 month. All but one ECG was normal. Methadone prescribing in favour of lower doses has been observed. QTc interval prolongation was not common.

Effective communication between primary and secondary care services is important in identifying cases and arranging ECGs.