Comparison of the effects of isoprenaline, orciprenaline, salbutamol and isoetharine on the cardiovascular system of anaesthetized dogs.

1. The intravenous injection of isoprenaline, orciprenaline, salbutamol and isoetharine increased heart rate in anaesthetized dogs. Log dose-response curves obtained with a series of doses of salbutamol and isoetharine were flatter than those for isoprenaline and orciprenaline. The order of activity of the drugs in increasing heart rate was isoprenaline, orciprenaline, and salbutamol=isoetharine.2. The injection into the external iliac artery of isoprenaline, orciprenaline, salbutamol and isoetharine produced dose dependent increases in femoral blood flow. Log dose-response curves for all drugs were parallel. The order of activity of the drugs was isoprenaline, salbutamol=isoetharine and orciprenaline.3. Salbutamol and isoetharine were less active than orciprenaline in increasing heart rate but more active in increasing femoral blood flow.4. These observations indicate that salbutamol and isoetharine have a greater effect on beta(2) than on beta(1)-adrenoceptors in the cardiovascular system.