Risk assessment of ractopamine and other beta-agonists used in animal feed

Beta-adrenoceptor agonists (beta-agonists) bind to beta-receptors on cardiac and smooth muscle tissues. They also have important actions in other tissues, especially bronchial smooth muscle, the liver and kidney. Beta-adrenoceptors normally bind to norepinephrine released by sympathetic adrenergic nerves, and to circulating epinephrine. Overall, the effect of beta-agonists is cardiac stimulation (increased heart rate, contractility, conduction velocity, relaxation) and systemic vasodilatation. 
Ractopamine is a compound, which participates on the nutrients repartitioning for purpose to increase lean deposition and to improve growth performance and carcass characteristics.
Ractopamine belongs into the group of beta-adrenoceptor agonists, which can negatively affect heart action, reactivity of lung tissue to the drugs, elongate therapy of asthma. Beta-agonists may also have anabolic effect. 
In terms of possible negative effect of residues of these substances contained in food of animal origin, EMEA concluded, than incorrect use of beta-adrenoreceptor agonists can represents serious risk for human health.