Use of Clenbuterol for Weight Loss The drug is specifically a selective beta-2 sympathomimetic, primarily affecting only one of the three subsets of beta-receptors. Of particular interest is the fact that Clenbuterol has little beta-i stimulating activity. Since beta-i receptors are closely tied to the cardiac effects of adrenoceptors, this allows to reduce reversible airway obstruction (and effect of beta-2 stimulation) with much less cardiovascular side effects compared to non-selective beta agonists. Clinical studies with Clenbuterol show it is extremely effective as a bronchodilator, with a low level of user complaints and high patient compliance Clenbuterol also exhibits an extremely long half-life in the body, which is measured to be approximately 34 hours long. This makes steady blood levels easy to achieve, requiring only a single or twice daily dosing schedule at most. This of course makes it much easier for the patient to use, and may tie into its high compliance rate. To spite that Clenbuterol is available in a wide number of other countries however; Clenbuterol has never been approved for use in the United States. The fact that there are a number of similar to Clenbuterol, effective asthma medications already available in this country may have something to do with this, as a prospective drug firm would likely not find it a profitable enough product to warrant undergoing the expense of the FDA approval process. Regardless, foreign Clenbuterol preparations are widely available on the U.S. black market.