The effect of intravenous dexamethasone on the white blood cell parameters in healthy horses

Abstract

Background: Dexamethasone, a synthetic glucocorticoid (GC), is widely used in equine medicine for the treatment of inflammatory and immune-mediated diseases. Given that GCs have an effect on the white blood cell (WBC) parameters, it is essential to differentiate drug induced hematological changes from those associated with pathology. This study aimed to provide insight on the extent and duration of WBC alterations following repeated dexamethasone administration in horses.

Objectives: To determine the effect of repeated intravenous (IV) administration of dexamethasone (0.06 mg/kg) on white blood cell (WBC) parameters in healthy horses.

Methods: Five mares from the Utrecht University Equine Hospital (UUEH) received dexamethasone (0.06 mg/kg bodyweight (BW)) IV at 0 and 24 hours and placebo at 48 and 72 hours. Blood sampling was performed at t = 0 h, 6 h, 12 h, 24 h, 30 h, 36 h, 48 h, 72 h, 96 h, and 192 h. Hematological parameters were analyzed at the University Veterinary Diagnostic Laboratory (UVDL) using an ADVIA 120 hematology analyzer. Linear mixed-effects models (LMMs) were applied to assess the effect of time on leukocytes, lymphocytes, neutrophils, myeloperoxidase index (MPXI), neutrophil X mean (NXM), neutrophil Y mean (NYM), basophils, eosinophils and monocytes.

Results: Following the first administration leukocyte and neutrophil counts increased, whereas lymphocyte, eosinophil, and monocyte counts decreased. Leukocyte and neutrophil counts peaked at 6 hours post-administration, and although declining thereafter, remained elevated 24 hours later. Lymphocyte and eosinophil counts also remained declined after 24 hours. Contrary, monocytes returned to baseline within 24 hours. A second dexamethasone administration, given 24 hours after the first, reinforced these patterns. MPXI, NXM, and NYM fluctuated significantly following dexamethasone administration. Hematological alterations resolved within 24 hours to 96 hours.

Conclusions: Repeated IV dexamethasone administration in healthy horses significantly alters WBC parameters, characterized by an increase in leukocyte and neutrophil counts and a decrease in lymphocyte, monocyte and eosinophil counts. Keywords: dexamethasone, glucocorticoid, white blood cell, equine