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Pharmacological particulars
Pharmacotherapeutic group: selective beta-2-adrenoreceptor agonists.
ATCvet code: QR03CC13
Pharmacodynamic properties
The product contains clenbuterol hydrochloride, which is a sympathomimetic amine which preferentially binds to β2 adrenoreceptors on cell membranes of the bronchi. This subsequently activates the enzyme adenylate cyclase in smooth muscle cells, thus providing intense bronchodilating properties and decreasing airway resistance with minimum effect on the cardiovascular system. The product has been shown to inhibit histamine release from mast cells in the lungs, and enhance mucociliary clearance in horses.
Pharmacokinetic properties
After oral administration in horses, clenbuterol is readily absorbed and maximum plasma concentrations reached within 2 hours of dosing.
Steady state concentrations in plasma are reached after 3-5 days treatment and range from 1.0–2.2 ng/ml.
The substance is rapidly distributed in tissues and metabolised primarily by the liver. Clenbuterol is the main excretory product and approximately 45% of the dose is eliminated unchanged in the urine. The kidneys excrete 70–91% of the total dose, and the remainder is eliminated in the faeces (6–15%).