[On the cardiac and hemodynamic side-effects of the beta 2-adrenergic broncholytic agent clenbuterol (Contraspasmin)].

Clenbuterol was tested for cardiac and haemodynamic side-effects by administering cumulative broncholytically efficient doses (continuous infusion) to anaesthetized dogs. The application of a dose of 1.25 micrograms/kg produced increased heart rate (+ 18%), increased maximum pressure-rise rate dp/dt max (+ 44%), increased heart time volume (+ 43%) and decreased total peripheral resistance (- 30%). The circulatory action of an isoprenaline dose of equivalent broncholytic efficacy (0.1875 micrograms/kg/min) led to more considerably marked changes of + 75%, - 117%, + 51% and - 33%, respectively. Parallel to the cardiovascular changes, Clenbuterol causes only a slight and non-significant increase of free fatty acids in the serum (+ 23%), whereas isoprenaline (with + 107%) has a strong beta 1-mimetic effect. In contrast to this, Clenbuterol stimulates the mobilization of glucose to a greater extent than isoprenaline. These findings show that Clenbuterol must be considered as a broncholytic agent of great beta 2-specificity; due to its long duration of action and its easy enteral absorption, it constitutes a true enrichment of therapeutics.