Clenbuterol Use in Horses (2023)

Clenbuterol HCl is a beta-2-adrenoceptor agonist; it is the only FDA-approved medication for horses with reversible bronchospasm and is often used to treat horses with inflammatory airway disease (IAD) and recurrent airway obstruction (RAO, commonly known as heaves).1 Although clenbuterol is often referenced as such, it is not a steroidal medication, but does possess some properties similar to those of anabolic steroids, such as promoting an increase in muscle mass. Due to these properties, clenbuterol has been used (in livestock and horse pharmacy applications) to increase lean muscle mass.

Clenbuterol is both a decongestant and a bronchodilator. Decongestants thin the blood to reduce blood pressure, while bronchodilators widen the vessels that carry oxygen, so the volume of oxygen in the blood increases. In some European and Latin American countries, clenbuterol is approved as an asthma drug for humans, but it has been banned for this purpose in the United States.


As with other β2 agonists, clenbuterol is believed to act by stimulating production of cyclic adenosine monophosphate (cAMP) through the activation of adenyl cyclase. β2 agonists produce more smooth muscle relaxation activity (ie, bronchial, vascular, uterine smooth muscle) than cardiac effects (β1). Clenbuterol appears to have secondary modes of action in horses, as it can inhibit the release of proinflammatory cytokines (eg, interleukin-1β and tumor necrosis factor α) from macrophages, increase mucociliary clearance, and reduce mucus production.2 Clenbuterol reduces the number and responsiveness of β2 receptors, but concurrent dexamethasone can prevent this effect.3

Clenbuterol has anabolic activity in humans and cattle. In horses, it can increase muscle mass, but any performance increases are offset by a negative ergonomic effect. The drug attenuates skeletal muscle changes (eg, heave lines) in horses with severe equine asthma (SEA). Clenbuterol has also been shown to decrease body fat percentage.2

(Video) The use of Clenbuterol ('Ventipulmin') in Chronic Obstructive Pulmonary Disease (COPD) in horses

In one study, when clenbuterol was administered IV to healthy horses, aerobic capacity was not improved, insulin levels were increased, and treadmill velocities for defined heart rates were reduced as compared with the control group. In a low-dose study, clenbuterol administration at 0.8 μg/kg every 12 hours for 14 days improved cardiac function in horses with SEA. Chronic administration of clenbuterol in horses can cause decreased aerobic performance, which may be due to effects on thermoregulation. Chronic clenbuterol administration in combination with exercise training has been known to diminish immune function by reducing numbers of monocytes and CD8+ T cells.2,3

In pregnant mares, clenbuterol can inhibit uterine tone and contractility,2 but these effects are not considered detrimental. In nonpregnant mares, clenbuterol’s effects on uterine contractility may potentially increase risks for mating-induced endometritis. Some studies have shown that clenbuterol can impair reproductive function in males.4

Potentials and Performance

It is important to realize that bronchodilator drugs such as do not cure disease. They provide symptomatic relief. Treatment of COPD requires reduction of the dust load to which the horse is exposed in combination with use of a potent corticosteroid such as dexamethasone.

Because it is a bronchodilator and a repartitioning agent, there has been great concern about clenbuterol’s ability to enhance performance. The amount of bronchodilation that occurs in normal horses is very small. In healthy human athletes, a measurable dilation of the airways induced by β2-agonist is not associated with an improvement in oxygen consumption. Likewise, intravenous administration of clenbuterol to thoroughbred horses 30 min before exercising on a treadmill does not improve oxygen consumption or cardiovascular function. Because the plasma concentration would be lower, it is even less likely that oral ad-ministration would have any effect on oxygen consumption.5

(Video) Doc Discusses: The Clenbuterol Controversy

The varying observations about the efficacy of clenbuterol in horses with COPD can be understood if one considers a) the relationship between lung function and clinical signs, and b) the pharmacology of clenbuterol. In COPD-affected horses with severe airway obstruction, measurable improvements in lung function can occur without a noticeable clinical improvement.5 When clenbuterol was administered intravenously and its effect was measured shortly thereafter, i.e., when plasma concentrations were high, the improvement in lung function was significant.

Adverse Effects

Drug side effects are unlikely with clenbuterol, but occasionally include muscle tremors, sweating, restlessness, urticaria, tachycardia, and ataxia, particularly early in the course of therapy. Creatine kinase elevations have been noted in some horses. A few studies performed in rats have shown small doses of clenbuterol to cause skeletal and cardiac muscle apoptosis. Studies in horses have not shown this adverse effect. One study found that 0.8 μg/kg PO twice daily for 21 days resulted in significant decreases in body fat with no loss in body weight. Adverse effects such as muscle tremors, tachycardia, and electrolyte abnormalities have been observed in humans after ingestion of animals that have been treated with clenbuterol.2

Clenbuterol Dosages

In horses, for management of airway obstruction, dosages of clenbuterol are as follows: Initially, 0.8 μg/kg PO twice daily for 3 days; if no improvement is noted, dose can be increased to 1.6 μg/kg PO twice daily for 3 days; if no improvement is observed, dose can be increased to 2.4 μg/kg PO twice daily for 3 days; if no improvement is noted, can be increased to 3.2 μg/kg PO twice daily for 3 days; if no improvement is noted, therapy should be discontinued. Recommended duration of therapy is 30 days, then it should be withdrawn and therapy re-evaluated.2

As adjunctive treatment for dystocia emergencies, dosages of clenbuterol are as follows: 300 μg per 500 kg mare IV, slowly. Clenbuterol’s fast onset of action when given IV allows the veterinarian to decide quickly if uterine relaxation will correct the problem. Clenbuterol is particularly useful when repelling the equine fetus to allow manipulation of the head and limbs. May be used in combination with sedatives, analgesics, and tranquilizers. Xylazine or detomidine may potentiate uterine relaxant effects of clenbuterol.2

(Video) LEGENDARY Steroid For Horses - What It Feels Like To Be On Equipoise


2Plumb’s Veterinary Drugs.

3Abraham G, Brodde OE, Ungemach FR. Regulation of equine lymphocyte beta-adrenoceptors under the influence of clenbuterol and dexamethasone. Equine Vet J. 2002;34(6):587-593.

4Kearns CF, McKeever KH. Clenbuterol and the horse revisited. Vet J. 2009;182(3):384-391.

(Video) Clenbuterol For Fat Loss, Is It Safe?

5Robinson, N.E., B.Vet.Med. Clenbuterol and the Horse. AAEP Proceedings/Vol. 46/2000, 229.

About NexGen Pharmaceuticals

NexGen Pharmaceuticals is an industry-leading veterinary compounding pharmacy, offering sterile and non-sterile compounding services nationwide. Unlike other veterinary compounding pharmacies, NexGen focuses on drugs that are difficult to find or are no longer available due to manufacturer discontinuance or have yet to be offered commercially for veterinary applications, but which still serve a critical need for our customers. We also specialize in wildlife pharmaceuticals, including sedatives and their antagonists, offering many unique options to serve a wide array of zoo animal and wildlife immobilization and anesthesia requirements.

Our pharmacists are also encouraged to develop strong working relationships with our veterinarians in order to better care for veterinary patients. Such relationships foster an ever-increasing knowledge base upon which pharmacists and veterinarians can draw, making both significantly more effective in their professional roles.


(Video) People Taking 'Horse Drugs' To Lose Weight

The information contained in this blog post is general in nature and is intended for use as an informational aid. It does not cover all possible uses, actions, precautions, side effects, or interactions of the medications shown, nor is the information intended as medical advice or diagnosis for individual health problems or for making an evaluation as to the risks and benefits of using a particular medication. You should consult your veterinarian about diagnosis and treatment of any health problems. Information and statements have not been evaluated by the Food and Drug Administration ("FDA"), nor has the FDA approved the medications to diagnose, cure or prevent disease. Medications compounded by NexGen Pharmaceuticals are prepared at the direction of a veterinarian. NexGen Pharmaceuticals compounded veterinary preparations are not intended for use in food and food-producing animals.

NexGen Pharmaceuticals, LLC does not recommend, endorse or make any representation about the efficacy, appropriateness or suitability of any specific dosing, products, procedures, treatments, services, opinions, veterinary care providers or other information that may be contained in this blog post. NEXGEN PHARMACEUTICALS, LLC IS NOT RESPONSIBLE NOR LIABLE FOR ANY ADVICE, COURSE OF TREATMENT, DIAGNOSIS OR ANY OTHER INFORMATION, SERVICES OR PRODUCTS THAT YOU OBTAIN THROUGH THIS BLOG POST.


1. CLENBUTEROL: The ULTIMATE Guide (Uses, Do's & Dont's)
(RxMuscle -- The Truth in Bodybuilding)
2. Flexineb 2 Portable Equine Nebulizer System Review
3. Clenbuterol - Fat Burning Drug - Doctor's Analysis of Side Effects & Properties
(Anabolic Doc)
4. Why Calcium & Phosphorus Is Important For Horse's?
(Pryde's EasiFeed)
6. This Is Everything You Need to Know About Clenbuterol
(Muscle for Life with Mike Matthews)
Top Articles
Latest Posts
Article information

Author: Terence Hammes MD

Last Updated: 24/06/2023

Views: 5363

Rating: 4.9 / 5 (69 voted)

Reviews: 84% of readers found this page helpful

Author information

Name: Terence Hammes MD

Birthday: 1992-04-11

Address: Suite 408 9446 Mercy Mews, West Roxie, CT 04904

Phone: +50312511349175

Job: Product Consulting Liaison

Hobby: Jogging, Motor sports, Nordic skating, Jigsaw puzzles, Bird watching, Nordic skating, Sculpting

Introduction: My name is Terence Hammes MD, I am a inexpensive, energetic, jolly, faithful, cheerful, proud, rich person who loves writing and wants to share my knowledge and understanding with you.