Effects of domperidone on digital laminar microvascular blood flow in clinically normal adult horses.

OBJECTIVE

To determine effects of domperidone and acepromazine maleate on microvascular blood flow in digital laminae of clinically normal adult horses.

ANIMALS

8 clinically normal adult horses (4 mares and 4 geldings).

PROCEDURES

In a 4-period crossover study, domperidone was administered PO at 1.1 mg/ kg and 5.5 mg/kg and IV at 0.2 mg/kg; acepromazine was administered IV at 0.04 mg/kg. The washout period between treatments was 1 week. A 3-minute measurement of laminar microvascular blood flow (LMBF) was obtained with laser Doppler flowmetry. Baseline measurements were obtained at -2, -1, and 0 hours prior to administration of drugs. Post-treatment measurements were obtained at 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 10, and 12 hours. Percentage change from baseline values in LMBF for each treatment was subsequently calculated.

RESULTS

Oral administration of domperidone at 1.1 mg/kg and 5.5 mg/kg significantly increased LMBF, compared with baseline values, beginning 4 hours after administration, and this effect persisted for at least 8 hours. Intravenous administration of domperidone at 0.2 mg/kg significantly increased LMBF, compared with baseline values, at 10 and 12 hours after administration. Administration of acepromazine (0.04 mg/kg, IV) significantly increased LMBF, compared with baseline values, at 3, 5, 8, and 10 hours after administration. No adverse effects of drugs were detected in any horse.

CONCLUSIONS AND CLINICAL RELEVANCE

Domperidone may be useful for preventing vasoconstriction and reduction in LMBF believed to occur in horses with laminitis, but additional research of the drug's effects in horses with laminitis is required.