Some dynamic and toxic effects of theophylline in horses.

The study looks into the effects of administering theophylline, in the form of aminophylline, to horses intravenously. The results showed that it led to increased urination, rapid heart rate, rapid breathing, and a heightened sensitivity to touch, sight, and sound, among other symptoms. However, it didn’t significantly affect other health aspects. The research suggests that theophylline is safest for horses when it’s concentration in the blood is below 15 micrograms/ml, and it’s best given orally or through the stomach.

Research Methodology and Findings

• The study was carried out on four mares, given theophylline via intravenous administration in the form of aminophylline at a dose of 10 mg/kg. Theophylline is a drug that is commonly used to treat respiratory diseases in horses due to bronchodilation property.
• The researchers observed that the administration of the drug led to diuresis or increased urine production. The peak urine production was recorded to be seven times the normal volume, making it a potent diuretic. This effect was observed mostly within the first hour after administration and lasted for about 6 hours.
• The drug also led to some noticeable side effects in the horses, such as tachycardia (increase in heart rate), polypnoea (increased breathing rate), and nervous symptoms. The nervous symptoms displayed as hypersensitivity to tactile, visual, and auditory stimuli. There were also instances of muscle tremors and sweating. Despite these side effects, the administration of the drug did not significantly impact arterial and central venous blood pressures, intrapleural pressure, red blood cell variables, or plasma proteins.

Implications and Recommendations

• In this study, it has been indicated that the safe upper limit for theophylline concentration in the horse’s blood is about 15 micrograms/ml.
• Based on the findings of the study, the researchers recommend the oral or intragastric route for theophylline administration. They suggest these alternatives because they are safer than the intravenous route, considering the side effects observed in the study.
• The results of this study contribute to the body of knowledge regarding the appropriate dosage and administration methods of theophylline in horses. Advancing this understanding can aid veterinary doctors in using this drug effectively while minimizing potential side effects in equine health care and management.