Extensive, random testing of steroid use in athletes around the world has led to the creation of a range of steroid "alternatives." These substitutes have emerged on illicit health foods, mail-order orders and "black market" drug networks to combat evasion of drug detection. The sympathetic amine Clenbuterol is one drug that has become very popular among athletes due to its purported tissue-building and fat-reducing properties. When athletes stop using steroids before competition to evade detection and avoid disqualification, athletes instead use Clenbuterol to slow muscle tissue degradation and promote fat burning to achieve the desired "sculpting" body shape. Clenbuterol is particularly attractive to women because it does not produce the anabolic, androgenic side effects of steroids.
Steroid “substitute” – Clenbuterol
Clenbuterol is a group of B2-adrenoceptor agonist compounds (albuterol, clenbuterol, albuterol (Salmeterol, Terbutaline)) that promotes the response of adrenergic receptors to epinephrine, norepinephrine, and other adrenergic amines in the blood. A review of animal studies (there are no human studies) on the effectiveness of clenbuterol shows that when sedentary, growing livestock are fed Clenbuterol at doses that exceed European regulations for the treatment of bronchial asthma in humans, Luo can reshape body composition by increasing the deposition of bone and cardiac protein and delaying fat accumulation (enhancing lipolysis). When fed long-term at therapeutic doses to thoroughbred racehorses, clenbuterol may increase lean body mass and decrease fat mass, possibly in part because clenbuterol alters plasma adiponectin and leptin levels. Clenbuterol has been used in animal studies to investigate its effects on muscle aging, immobility, malnutrition, and pathological tissue wasting. Under the above circumstances, b2-agonists exhibit a specific growth-promoting effect on skeletal muscle. In rats, clenbuterol can change the distribution of muscle fiber types, resulting in an increase in the size and proportion of type 2 muscle fibers. The reason Clenbuterol increases muscle size in animals may be because it reduces protein breakdown and increases protein synthesis.
Potential adverse effects on muscle, bone and cardiovascular function
Female rats were subcutaneously injected with clenbuterol or an equal volume of clenbuterol-free carrier solution every day for 14 days. Injection of clenbuterol can increase 1. muscle mass, 2. absolute maximum contraction force, and 3. fast and slow contraction. Contractile muscle fiber hypertrophy. One study to the contrary showed that clenbuterol accelerates muscle fatigue during short-term, intense exercise. Other studies have observed similar positive and negative effects of clenbuterol. For example, by measuring muscle contractility, it was found that regular exercise combined with clenbuterol delayed the progression of muscular dystrophy in mdx mice. The clenbuterol group experienced increased muscle fatigue and cell deformities that did not occur in the regular exercise group. Based on the side effects on muscle structure and function, it may be concluded that in animals, although clenbuterol increases muscle protein content, it has a negative impact on endurance exercise. Administration of clenbuterol induced excessive muscle growth in young male rats but also inhibited longitudinal bone growth. This is related to the fact that Clenbuterol can accelerate epiphyseal closure in growing animals, so the use of Clenbuterol in prepubertal children and adolescents must be prohibited.
Evaluation of echocardiograms in female Standardbred horses demonstrates that long-term use of clenbuterol, even at subtherapeutic levels, changes the structural dimensions of the heart in a manner that impairs cardiac function. The effects occur regardless of horse racing activity or not. Furthermore, clenbuterol causes post-exercise aortic dilation to the extent that it increases the risk of aortic rupture and sudden death. When clenbuterol is used in combination with aerobic training, the plasma volume-increasing effects of normal training on standard competition horses are attenuated, which is associated with a reduced effect of aerobic training and reduced recovery.
Clenbuterol has not been approved for human use in the United States, but in other countries it is commonly used clinically as an inhaled bronchodilator to treat obstructive pulmonary disease. Short-term side effects reported from accidental "overdoses" in humans resulting from the accidental consumption of meat contaminated with clenbuterol include: skeletal muscle tremors, anxiety, heart palpitations, dizziness, nausea, muscle cramps, rapid heart rate, and Headache. Despite these adverse effects, clenbuterol can be beneficial to humans when used under medical supervision, including treating muscular dystrophy, immobilization syndrome, and aging. Unfortunately, there is currently no data on the potential toxicity levels or effectiveness and safety of clenbuterol with long-term use.
Clearly, clenbuterol is an unproven substance and cannot be recommended for use in performance-enhancing drugs.