Oral reserpine administration in horses results in low plasma concentrations that alter platelet biology.

This research investigates the effects of the drug reserpine on horses, specifically its impact on platelet function and blood coagulation. The findings indicate that reserpine, commonly used for long-term tranquilisation, leads to low plasma concentrations and extensive platelet activity in horses.

Methodology

• The research was carried out as an experimental controlled study.
• The researchers administered oral doses of reserpine (2.5 mg per horse, once only) to six healthy adult horses, then studied the pharmacokinetics – how the drug is absorbed, distributed, metabolized, and excreted by the body.
• Plasma samples were collected and the concentrations of reserpine were determined using precise analytical methods (UPLC-MS/MS).
• The researchers then analyzed the impact of various concentrations of reserpine on platelets – components of blood that aid coagulation – by conducting aggregation, adhesion, and releasate assays.
• These assays tested for serotonin and thromboxane B, substances that influence platelet function, in platelets exposed to reserpine. Aspirin was used as a negative control and saline for the unexposed control.

Results

• Administering oral reserpine led to low plasma concentrations and a prolonged half-life in horses. The half-life of a drug refers to how long it takes for the concentration of the drug in the body to reduce by half – in this case, it was 23.6 hours on average.
• Platelets exposed to reserpine showed increased adhesion and aggregation compared to control groups. They also exhibited different levels of serotonin and thromboxane B, compared to those not exposed to reserpine or exposed to higher reserpine concentrations.

Conclusions

• The study suggests that even with low plasma concentrations, reserpine can significantly alter platelets’ function in horses, likely due to the impact on serotonin release and reuptake.
• Such changes potentially prime platelets for activation and the release of thromboxane B, which leads to the evident hypercoagulability in the horses’ blood.
• The findings suggest that blood harvest for biological processing should occur before the administration of reserpine to prevent its effects on platelets.
• However, the small sample size and the exclusive use of in vitro platelet experiments restrict the generalizability of the results. Further studies will be needed to fully understand the effects of reserpine in a clinical setting.