Effect of β‐blocking agents with and without intrinsic sympathomimetic activity on work efficiency in healthy men

Abstract

In order to evaluate the effect of beta-blocking agents with and without intrinsic sympathomimetic activity (ISA) on work efficiency in healthy subjects, we studied the haemodynamic and gas exchange parameters, as well as blood lactate concentrations, during a graded maximal bicycle exercise test performed after perorally given propranolol (PRO) and pindolol (PIN) in seven healthy men. The medications (PRO: 80 mg x 2/day, PIN: 10 mg x 2/day, for seven days) were given in a placebo (PLA) controlled, double-blind, randomized, cross-over fashion. Both the drugs reduced heart rate and blood pressure during exercise equally compared with the placebo. The oxygen uptake at submaximal work loads, as well as at the maximum, was constantly and equally reduced by PRO and PIN compared with PLA. The anaerobic threshold was reached at a slightly lower oxygen uptake for both the drugs compared with the placebo (P < 0.05). No significant difference was, however, observed in the work levels at which the ventilatory anaerobic threshold was reached. Moreover, the gross efficiency, i.e. the amount of work performed at a certain energy consumption level (aerobic + anaerobic), was increased by both PRO (26.7 +/- 0.5%, P < 0.02 vs PLA: 24.7 +/- 0.5%) and PIN (26.5 +/- 0.5%, P < 0.05 vs PLA) at a submaximal work load of 240 W. The results indicate that beta-blocking agents propranolol and pindolol slightly and equally reduce maximal work performance, but increase the efficiency of submaximal work in a way that a certain amount of external work can be done with smaller consumption of oxygen. These findings may contribute to the benefit of beta-blocking agents in patients with coronary heart disease.

Aerobic capacity in patients with chronic liver disease: Very modest effect of liver transplantation

“…Peak VO 2 was unaffected by liver transplantation in patients initially treated with these agents. This observation is consistent with several studies showing the lack of any change in exercise tolerance and peak VO 2 in cirrhotic patients after the initiation of beta-blocker treatment [16,17]. As Hb and SaO 2 were unchanged after OLT in patients initially treated by bblocker, the persistent alteration in aerobic capacity in this group after OLT may be related to impaired peripheral oxygen diffusion and utilization processes.…”

Physical activity and liver diseases

“…The same researchers showed that pretreatment with propranolol (the most commonly used nonselective beta‐blocker for portal hypertension treatment) blunts the aggravating effects of acute exercise on portal pressure . In this regard, it should be noted that despite their negative chronotropic and inotropic effect, initiation of beta‐blocker therapy is not associated with a worsening in aerobic capacity, except when portopulmonary hypertension is present, and in cirrhosis nonselective beta‐blocker discontinuation post‐LT did not lead to improvement in aerobic capacity.…”

Reduced Hemodynamic Responses to Physical and Mental Stress Under Low-Dose Rilmenidine in Healthy Subjects

“…Although beta-blockers can have similar effects on blood pressure during physical and mental stress, when compared to rilmenidine, there are some issues that must be taken into account in this scenario. Beta-blockers are known to reduce maximal exercise tolerance in humans [38]. In the present study, rilmenidine at a low dose did not affect exercise tolerance of healthy individuals.…”