Clenbuterol toxicosis in three Quarter Horse racehorses after administration of a compounded product.

The research explores the harmful effects of an overdose of clenbuterol, a veterinary bronchodilator, in three Quarter Horse racehorses. The study concludes that improper dosage of this drug can result in severe health complications, and emphasizes the risks of using compounded, non-prescribed medications.

Overview of Research and Methodology

• The study began with three Quarter horses that were suspected of a clenbuterol overdose. Their symptoms were noted 12 to 24 hours after they were orally administered a compounded product of the drug.
• Vital signs and abnormalities were recorded for each horse. Key symptoms across all three horses included sinus tachycardia (a condition where the heart beats at an abnormally rapid rate), muscle tremors, excessive sweating (hyperhidrosis), and colic (severe, often fluctuating pain in the abdomen, usually caused by gas or other digestive disorders).
• A serum biochemical analysis was carried out, revealing high levels of blood sugar (hyperglycemia), build-up of nitrogen waste products in the body (azotemia), and increased creatine kinase activity, which points to muscle damage.
• A test known as liquid chromatography-electrospray tandem mass spectrometry confirmed and quantified the presence of clenbuterol both in the horses’ serum and the compounded product.

Treatment and Results

• All three horses were administered propranolol, a medication often used to control heart rate in humans, to counteract the β-adrenergic effects of clenbuterol. This led to a temporary decrease in heart rates but did not entirely alleviate the clinical signs in the patients.
• Other supportive treatments, including intravenous crystalloid fluids, were also given to the horses. Despite these measures, two horses were euthanized due to complications while one recovered and was discharged after four days of hospitalization.
• Postmortem examinations revealed skeletal and cardiac muscle necrosis (cellular death) in the two euthanized horses, with the highest clenbuterol concentrations found in their livers. Acute renal failure, laminitis (a painful and potentially crippling condition affecting the horse’s hoof), rhabdomyolysis (a syndrome due to a direct or indirect muscle injury), and cardiomyopathy (disease of the heart muscle) were identified as the fatal complications associated with the overdose.

Conclusions

• Clenbuterol, which is a β(2)-adrenergic receptor agonist used in veterinary practice as a bronchodilator, can potentially lead to severe symptoms like sustained tachycardia, muscle tremors, hyperglycemia, and cardiac and skeletal muscle necrosis if given in excess doses.
• The research highlighted the significant risks associated with the use of non-prescribed compounded medications, where the exact composition and dose might vary, possibly leading to overdose and severe side effects.