Antiarrhythmic potency of naloxone determined by a screening test using the isolated ischaemic perfused rat heart preparation

The antiarrhythmic potency of naloxone was determined by a screening test using the isolated ischaemic perfused rat heart preparation. The cardiac antiarrhythmic potency CAP50 with 95% confidence limit was 818 nmole/heart (646-985) and relative potency 0.22 compared with 0.35, 0.51 and 1.0 for lidocaine, quinidine and propranolol, respectively. These values are of clinical importance when considering the use of naloxone as an antiarrhythmic agent.