Topic:Clenbuterol
Clenbuterol is a beta-2 adrenergic agonist commonly used in veterinary medicine to manage respiratory conditions in horses due to its bronchodilator properties. It facilitates breathing by relaxing the muscles in the airways, thereby improving airflow to the lungs. Clenbuterol is also known to have anabolic effects, which has led to its misuse in some contexts for enhancing muscle mass and performance in horses. The use of clenbuterol is regulated in competitive equestrian sports due to its potential impact on performance. This page compiles peer-reviewed research studies and scholarly articles that explore the pharmacology, therapeutic applications, regulatory considerations, and potential side effects of clenbuterol in equine practice.
Effect of Clenbuterol on Muscle Activity During Exercise in Standardbred Horses. Clenbuterol (β agonist) is a commonly administered bronchodilator in race and performance horses. While long-term administration can alter exercise performance and muscle properties, little is known about its effects on these parameters following short-term administration. A single dose of clenbuterol (0.80 µg/kg) was expected to alter muscle activity of the extensor carpi radialis, semitendinosus, and longissimus dorsi during submaximal exercise. Eight mature Standardbred horses exercised for 2 minutes at 5 m/s on a high-speed treadmill following clenbuterol dosing (clenbuterol) or no dosin...
The medication violations in racehorses at Louisiana racetracks from 2016 to 2020. The number of publications for most common drug violations in racehorses is limited. This study reports the most common medication violations in racehorses at four major racetracks in Louisiana between 2016 and 2020. During this 5-year period, 27,237 blood samples and 25,672 urine samples collected during the course of normal race meeting activities were analysed by initial screening procedure utilizing Liquid Chromatography Mass Spectrometry (LC-MS/MS). Following initial screening, suspect samples were subject to quantitative or semi- quantitative confirmation analysis by LC-MS/MS. The total ...
The Effect of the Clenbuterol-β2-Adrenergic Receptor Agonist on the Peripheral Blood Mononuclear Cells Proliferation, Phenotype, Functions, and Reactive Oxygen Species Production in Race Horses In Vitro. Clenbuterol, the β2-adrenoceptor agonist, is gaining growing popularity because of its effects on weight loss (i.e., chemical liposuction). It is also popular in bodybuilding and professional sports, due to its effects that are similar to anabolic steroids. However, it is prohibited by anti-doping control. On the other hand, it is suggested that clenbuterol can inhibit the inflammatory process. The cells from 14 untrained and 14 well-trained race horses were collected after acute exercise and cultured with clenbuterol. The expressions of CD4, CD8, FoxP3, CD14, MHCII, and CD5 in PBMC, and reac...
Relaxing effects of clenbuterol, ritodrine, salbutamol and fenoterol on the contractions of horse isolated bronchi induced by different stimuli. β-adrenoceptor agonists are considered the most effective drugs to counteract bronchoconstriction in horses with asthma, but only clenbuterol is commonly employed in clinical practice. We evaluated the effects of different selective β agonists: clenbuterol, ritodrine, salbutamol, and fenoterol on the contractions of isolated bronchial muscle of horses induced by electrical field stimulation (EFS), carbachol, histamine, and KCl. All β agonists reduced the amplitude of contraction induced by the different stimuli but with variable efficacy and potency. Fenoterol and salbutamol were more effec...
Development of an immunochromatographic assay for the β-adrenergic agonist feed additive zilpaterol. Zilpaterol is a β-adrenergic agonist feed additive approved in the United States to increase weight gain and improve feed efficiency of cattle. A zilpaterol immunochromatographic assay was developed as an economical and user-friendly rapid detection method for zilpaterol and validated using urine and tissue samples derived from animal studies. The assay sensitivity was 1.7-23.2 ng g or mL across a variety of feed and animal matrices and did not cross-react with clenbuterol or ractopamine. No sample pre-treatment of cattle and sheep urine was needed, but horse urine and feed required dilution;...
Doping control analysis of 121 prohibited substances in equine hair by liquid chromatography-tandem mass spectrometry. Equine hair is becoming an increasingly popular biological matrix for doping control of horse sports; one of the reasons for this is the significantly longer detection window hair can offer. Hair analysis opens up the opportunity for longitudinal monitoring of drug exposure which would otherwise not be possible with the more traditional and common biological matrices, such as urine and blood. As such, there is a need for more multi-target screening methods covering a broad range of prohibited substances in equine hair at the required sensitivities for equine doping control. This paper describe...
Detection of prohibited substances in equine hair by ultra-high performance liquid chromatography-triple quadrupole mass spectrometry – application to doping control samples. The detection of drugs in human hair samples has been performed by laboratories around the world for many years and the matrix is popular in disciplines, such as workplace drug testing. To date, however, hair has not become a routinely utilised matrix in sports drug detection. The analysis of hair samples offers several potential advantages to doping control laboratories, not least of which are the greatly extended detection window and the ease of sample collection and storage. This article describes the development, validation, and utilisation of a sensitive ultra-high performance liquid chro...
Differential expression of skeletal muscle genes following administration of clenbuterol to exercised horses. Clenbuterol, a beta2-adrenergic receptor agonist, is used therapeutically to treat respiratory conditions in the horse. However, by virtue of its mechanism of action it has been suggested that clenbuterol may also have repartitioning affects in horses and as such the potential to affect performance. Clenbuterol decreases the percent fat and increases fat-free mass following high dose administration in combination with intense exercise in horses. In the current study, microarray analysis and real-time PCR were used to study the temporal effects of low and high dose chronic clenbuterol administr...
Rhabdomyolysis Secondary to Clenbuterol Use and Exercise. The literature regarding rhabdomyolysis secondary to illicit drug use is sparse. Clenbuterol is a bronchodilator approved for veterinary use, which in high doses can increase protein deposition and lipolysis similarly to anabolic steroids, and is thereby abused for bodybuilding and weight loss effects. Clenbuterol has previously been described in case reports to be cardiotoxic, with patient presentations similar to overdoses of sympathomimetic substances, but reports of rhabdomyolysis are limited to a single case series in horses. Methods: We report the first case of rhabdomyolysis secondary t...
Effect of long-term oral administration of a low dosage of clenbuterol on body fat percentage in working and nonworking adult horses. To determine the anabolic and lipolytic effects of a low dosage of clenbuterol administered orally in working and nonworking equids. Methods: 8 nonworking horses and 47 polo ponies in active training. Methods: Each polo pony continued training and received either clenbuterol (0.8 μg/kg) or an equal volume of corn syrup (placebo) orally twice daily for 21 days, and then was evaluated for another 21-day period. Nonworking horses received clenbuterol or placebo at the same dosage for 21 days in a crossover trial (2 treatments/horse). For working and nonworking horses, percentage body fat (PBF) w...
Confirmation and quantification of clenbuterol in horse urine using liquid chromatography tandem mass spectrometry triple quadrupole. Clenbuterol (CLE) is used in horses as a bronchodilator and for its anabolic steroid-like effects. CLE is a Class 3 drug according to current Association of Racing Commissioners International (ARCI) Uniform Classification Guidelines. The Racing Medication and Testing Consortium recommended a urine CLE threshold of 140 pg/mL after careful scientific review of the results of studies describing the disposition of CLE in the horse and this threshold was adopted by the ARCI. Enzyme-linked immunosorbent assay was previously used to screen samples for CLE in Illinois, but could not detect such low co...
Concomitant inhibition of primary equine bronchial fibroblast proliferation and differentiation by selective β2-adrenoceptor agonists and dexamethasone. Altered airway cell proliferation plays an important role in the pathogenesis of human bronchial asthma and chronic obstructive pulmonary disease (COPD) as well as the equine recurrent airway obstruction (RAO) with consistent changes, i.e. narrowing the airway wall, explained by proliferation and differentiation of fibroblasts. In permanent cell lines, it has been suggested that β2-adrenoceptor agonists and glucocorticoids regulate cell proliferation via the β2-adrenoceptor pathway; indeed, no study was carried out in fresh isolated primary equine bronchial fibroblasts (EBF). We characterize...
Effect of clenbuterol on tracheal mucociliary transport in horses undergoing simulated long-distance transportation. Pneumonia is observed in horses after long-distance transportation in association with confinement of head position leading to reduction in tracheal mucociliary clearance rate (TMCR). Objective: Clenbuterol, a beta-2 agonist shown to increase TMCR in the horse, will ameliorate the effects of a fixed elevated head position on large airway contamination and inflammation in a model of long-distance transportation model. Methods: Six adult horses. Methods: A cross-over designed prospective study. Horses were maintained with a fixed elevated head position for 48 hours to simulate long-distance tran...
Effects of oral clenbuterol on the clinical and inflammatory response to endotoxaemia in the horse. Pro-inflammatory cytokines, such as IL-1β and TNFα, play a major role in activating leukocytes and endothelial cells during the systemic inflammatory response to endotoxin in the horse. β2 agonist drugs, such as clenbuterol, inhibit leukocyte activation. This study aimed to determine the effects of oral clenbuterol on clinical and leukocyte responses, including production of TNFα, in an in vivo endotoxin challenge model. In a randomised crossover design, horses received either clenbuterol or a placebo product prior to the administration of low dose endotoxin (30 ng/kg over 30 min). Clinica...
Effects of clenbuterol administration on serum biochemical, histologic, and echocardiographic measurements of muscle injury in exercising horses. To determine the effects of clenbuterol, at a dosage of up to 3.2 μg/kg for 14 days, PO, on skeletal and cardiac muscle in healthy horses undergoing treadmill exercise. Methods: 12 healthy horses from 3 to 10 years old. Methods: Horses were randomly assigned to a control group (n = 6) or clenbuterol group (6) and received either saline (0.9% NaCl) solution or clenbuterol, PO, every 12 hours for 14 days. Horses were subjected to submaximal treadmill exercise daily during treatment. Muscle biopsy specimens were collected before and after treatment for determination of apoptosis. Echocardiograph...
Effect of prolonged administration of clenbuterol on airway reactivity and sweating in horses with inflammatory airway disease. To determine whether prolonged administration of clenbuterol results in tachyphylaxis, specifically regarding its bronchoprotective properties and effect on sweating in horses. Methods: 8 Thoroughbreds with inflammatory airway disease. Methods: In a crossover design, horses received clenbuterol (0.8 μg/kg, p.o., q 12 h) or placebo for 21 days, with a washout period of ≥ 30 days between the 2 treatments. Airway reactivity was evaluated by use of flowmetric plethysmography and histamine broncho-provocation before (day 0; baseline) and every 7 days after the start of treatment. Sweat function ...
Clenbuterol toxicosis in three Quarter Horse racehorses after administration of a compounded product. 3 Quarter Horse racehorses were examined for suspected clenbuterol overdose 12 to 24 hours after administration by mouth of a compounded clenbuterol product. Results: All horses developed sinus tachycardia, muscle tremors, hyperhidrosis, and colic. Abnormalities on serum biochemical analysis included hyperglycemia, azotemia, and high creatine kinase activity. The presence of clenbuterol in the serum of all 3 horses and in the product administered was confirmed and quantified by use of liquid chromatography-electrospray tandem mass spectrometry. Results: Propranolol (0.01 mg/kg [0.005 mg/lb], I...
Detection of urine and blood clenbuterol following short-term oral administration in the horse. The pharmacokinetics of clenbuterol in equine urine and blood was investigated. Methods: Urine and blood samples were collected following 3-day multiple oral administrations. The samples were examined using enzyme-linked immunosorbent assay and further confirmed by solid phase extraction and capillary electrophoresis. Results: Urinary clenbuterol was detectable until day 14 after the last dose. The urinary excretion of clenbuterol was characterized by a biphasic pattern. The half-lives of the bi-exponential elimination (t(1/2alpha) and t(1/2beta)) for urinary clenbuterol were about 12.1 and 48...
Antibodies conjugated with new highly luminescent Eu3+ and Tb3+ chelates as markers for time resolved immunoassays. Application to simultaneous determination of clenbuterol and free cortisol in horse urine. Highly luminescent Eu(3+) and Tb(3+) complexes of 10-[4-(3-isothiocyanatopropoxy)benzoylmethyl]-1,4,7,10-tetraazacyclododecane-1,4,7 triacetic acid Eu(3+) is a subset of 1 and Tb(3+) is a subset of 1 were conjugated with a goat anti-rabbit IgG and a rabbit anti-mouse IgG, respectively, and applied as markers in a time resolved immunoassay for simultaneous quantitative determination of anabolic compounds clenbuterol (CL) and hydrocortisone (HC). The assay was performed in horse urine, using a monoclonal antibody specific to CL and a rabbit polyclonal antibody specific to the free HC. These lant...
Clenbuterol and the horse revisited. Clenbuterol is a beta(2)-agonist and potent selective bronchodilator that is used to treat bronchospasm in the horse. The drug is normally administered to horses orally as a syrup formulation. Once absorbed into the systemic circulation, clenbuterol has the potential to cause many side effects, including a repartitioning effect and major alterations in cardiac and skeletal muscle function. Recent studies have also reported that clenbuterol can affect bone and the immune, endocrine and reproductive systems. A great deal of information has been published on the beneficial effects of short term t...
Reactivity of equine airways–a study on precision-cut lung slices. A study was performed to evaluate the use of precision-cut lung slices (PCLS) for studies on the contraction of equine airways. Lungs of 10 horses were taken to prepare PCLS of approximately 250 microm from equine lung tissue using a special microtome. The lung slices were cultured and the enclosed small airways were monitored using a microscope with coupled digital camera, which was used to determine the airway luminal area and diameter from digital images. As indicated by the beating of the ciliated epithelium and reactivity of airways on methacholine challenge, the tissue slices were found ...
Clenbuterol affects the expression of messenger RNA for interleukin 10 in peripheral leukocytes from horses challenged intrabronchially with lipopolysaccharides. On four occasions, four horses with heaves and four horses with small airway inflammatory diseases inhaled 0.9% saline based aerosol mixtures with or without lipopolysaccharides (LPS). Prior to the first saline and LPS inhalation, horses were untreated, while three and a half days prior to the third and forth inhalation horses had received 0.8 microg/kg clenbuterol intravenously twice daily. The messenger RNA (mRNA) expression of tumour necrosis factor-alpha (TNF-alpha), interleukin (IL)-1beta, IL-4, IL-6, IL-8, IL-10 and interferon- gamma (IFN- gamma) was investigated by RT-PCR, all of which ...
The effect of aerosolized and intravenously administered clenbuterol and aerosolized fluticasone propionate on horses challenged with Aspergillus fumigatus antigen. Beta-agonists have been shown to display anti-inflammatory properties in several experimental models. The aim of this study was to investigate the anti-inflammatory properties of clenbuterol (CB), administered either intravenously or by aerosol, in comparison with fluticasone propionate (FP) in recurrent airway obstruction (RAO)-susceptible horses. Eight horses, of which five were known to be susceptible to RAO, underwent an inhalation challenge with Aspergillus fumigatus (AF) antigen and were treated with CB intravenously, CB by aerosol, or FP by aerosol. Twenty-four hours after the challenge...
The anti-inflammatory effects of IV administered clenbuterol in horses with recurrent airway obstruction. Cyclic AMP elevating agents have been shown to exhibit anti-inflammatory properties in addition to functions such as bronchodilation. The aim of this study was to investigate this dual action of clenbuterol (CB; Ventipulmin) on horses affected with recurrent airway obstruction (RAO). Seven RAO susceptible horses received inhalation challenges with aerosolised lipopolysaccharide (LPS), hay dust suspension (HDS) and Aspergillus fumigatus antigen (AF) with and without prior treatment with intravenous CB. Data showed that CB exerted significant beneficial effects on lung function, total cell count...
Changes in adipopnectin, leptin, and fat mass after clenbuterol treatment in horses. Adipose tissue plays complex role(s) in metabolic and endocrine control. To date, little work has been done in the horse regarding adipocytokines. Objective: This study was conducted to determine whether therapeutic levels of chronic beta-agonist administration, exercise, or both could alter their concentrations. Methods: A total of 23 standard-bred mares were divided into four experimental groups: clenbuterol (2.4 microg.kg(-1) bw twice daily for 8 wk) plus exercise (8 wk, 20 min.d(-1) at 50% VO2max; CLENEX; N = 6), clenbuterol only (CLEN; N = 6), exercise only (EX; N = 5), and control (CON; ...
Evaluation of cytokine production by equine alveolar macrophages exposed to lipopolysaccharide, Aspergillus fumigatus, and a suspension of hay dust. To evaluate cytokine production by equine alveolar macrophages after exposure to lipopolysaccharide (LPS), Aspergillus fumigatus, and hay dust, and determine the effect of clenbuterol on the cytokine response. Methods: 6 horses. Methods: Alveolar macrophages were exposed to PBS solution (negative control), LPS, hyphae and conidia of Aspergillus fumigatus (AF), or a suspension of hay dust (HDS) and incubated for 24 hours at 37 degrees C. Concentrations of tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta were measured in the supernatant. The procedure was repeated with cells that wer...
Effect of clenbuterol on the clearance of particles of charcoal (4 to 90 microm) from the uteri of mares. The failure of clearance mechanisms in the mare's uterus results in persistent inflammation and is considered a major cause of subfertility. Eighteen mares, of which three were susceptible to endometritis and four had been ovariectomised, underwent charcoal clearance testing to evaluate their clearance mechanisms. This consisted of installing 500 mg of charcoal (particle size 4 to 90 microm) added to 50 ml of phosphate-buffered saline (PBS) into the uterus. Forty-eight hours later the uterus was flushed out with 0.0012 per cent methylene blue in 50 ml of PBS for determination of the diluting f...
Effect of chronic clenbuterol administration and exercise training on immune function in horses. Effects of longitudinal exercise training and acute intensive exercise (simulated race test) on immune function have not been reported in horses. Clenbuterol, a beta2-adrenergic agonist, is used to manage inflammatory airway disease in horses. This study investigated the interaction of 8 wk of exercise training with or without 12 wk of clenbuterol administration in horses. Twenty-three untrained standardbred mares (10 +/- 3 yr, Mean +/- SE) were used and divided into four experimental groups. Horses given clenbuterol plus exercise (CLENEX; n = 6) and clenbuterol alone (CLEN; n = 6) received 2....
Are so many adrenergic receptor subtypes really present in domestic animal tissues? A pharmacological perspective. Adrenergic receptors (ARs) are the cellular membrane binding sites through which natural catecholamines and sympathomimetic drugs exert their physiological and pharmacological effects. In recent decades, studies to clarify the distribution and function of ARs have been performed mostly on cultured cells, laboratory animals and human target tissues, but little is known about these aspects in domestic animals. This review focuses on AR structure, classification and signalling pathways and on AR subtype distribution in target tissues of some domestic animals, namely dogs, horses and bovines. In t...