In vivo administration of acepromazine or promethazine to horse decreases the reactive oxygen species production response of subsequently isolated neutrophils to stimulation with phorbol myristate acetate

The previous experiments have shown that some phenothiazines have
antioxidant and anti-inflammatory properties in vitro. In this study the
inhibition of the production of reactive oxygen species (ROS) by neutrophils
was studied in two groups of horses, which received a dose of 0.1 mg⁄ kg of
either acepromazine or promethazine intravenously. Blood samples were
collected before (T0) and 0.5, 1, 3 and 5 h after drug administration. The
chemiluminescence (CML) response of neutrophils was measured ex vivo in the
presence of luminol for a period of 10 min and the maximum CML value (peak
value) recorded. There was a significant inhibition of the ROS production in the
acepromazine treated group (49% inhibition) at 5 h after administration and in
the promethazine group (24% inhibition) at 3 h after administration (P < 0.05
vs. T0). These findings are of therapeutic relevance in the use of phenothiazines
in equine patients with inflammatory diseases where neutrophil activation and
ROS production are implicated.