beta-Adrenoceptor hypersensitivity after stopping oxprenolol: discrepant findings not attributable to methodology

Using isoprenaline and glyceryl trinitrate (GTN) induced tachycardia we have compared the rebound beta-adrenoceptor hypersensitivity on stopping slow-release and conventional oxprenolol in young normotensive subjects. Heart rate on standing with GTN rose after stopping slow-release and conventional oxprenolol to peak levels on day 2 or 3 significantly greater than corresponding control levels off treatment on day 5. The isoprenaline CD25 (the dose required to increase heart rate by 25 beats/min) fell after stopping conventional oxprenolol to a significantly lower level on day 3 than the control level off treatment on day 5. Contrary to a recent report describing no rebound beta-adrenoceptor hypersensitivity on stopping slow-release oxprenolol we have demonstrated it after stopping slow release as well as conventional oxprenolol.