Pharmacokinetics and metabolic effects of triamcinolone acetonide and their possible relationships to glucocorticoid-induced laminitis in horses.

The research investigates the effects of triamcinolone acetonide on horses’ metabolism and how it could potentially lead to a condition called laminitis, caused by the drug’s long-term action on the animal’s system.

Pharmacokinetics of Triamcinolone Acetonide in Horses

• The research was conducted to understand the pharmacokinetics (what the body does to a drug) of triamcinolone acetonide. After administering the drug intravenously, the researchers found that its distribution in the horses’ bodies conformed to a three-compartment model. This means that the drug first rapidly disseminates to the central compartment (the heart, lungs, liver and kidneys) and is then gradually eliminated in two phases, first quickly and then more slowly.
• The half-life (the time required for the concentration of the drug to reach half of its original value) was found to be 83.5 minutes for the rapid elimination phase and approximately 12 hours for the slower one. The measure (Vss/Vc) – 1 resulted in 12.3, indicating that the drug spreads extensively into bodily tissues.

Metabolic Effects of Triamcinolone Acetonide

• Whether delivered intravenously or intramuscularly, triamcinolone acetonide induced a sustained period of hyperglycaemia (high blood sugar), hyperinsulinaemia (excess insulin in the blood) and hypertriglyceridaemia (high levels of triglycerides in the blood). However, significant changes in plasma glucagon and serum non-esterified fatty acids were not found.
• The raised blood sugar levels were attributed to tissues using less glucose and an increase in gluconeogenesis (the production of glucose from non-carbohydrate sources).
• The effect on sugar metabolism lasted for 3-4 days after an upper-limit recommended dose of 0.05 mg/kg was administered intramuscularly. It persisted for 8 days when a dose of 0.2 mg/kg was given.

Ties with Laminitis in Horses

• Previous research has associated inhibition of glucose metabolism with the development of laminitis in horses. Given the observation of prolonged metabolic effects of triamcinolone acetonide, the study implies the likelihood of the drug-induced laminitis in cases of higher than advised doses or repetitions of doses.
• Laminitis is an inflammation of sensitive layers of tissue (laminae) inside the horse’s hoof. In severe cases, it can lead to lameness or deformed hooves.