Gentamicin-induced sensorineural auditory loss in healthy adult horses.

BACKGROUND: Irreversible sensorineural auditory loss has been reported in humans treated with aminoglycosides but not in horses. OBJECTIVE: Investigate if auditory loss occurs in horses treated using the recommended IV daily dosage of gentamicin for 7 consecutive days. ANIMALS: Ten healthy adult horses (7-15 years; females and males, 5 each). METHODS: Prospective study. Physical and neurological examinations and renal function tests were performed. Gentamicin sulfate was administered at a dosage of 6.6 mg/kg via the jugular vein on alternating sides for 7 days. Gentamicin peak and trough concentrations were measured. Horses were sedated using detomidine hydrochloride IV to perform brainstem auditory evoked responses (BAER) before the first dose, immediately after the last dose, and 30 days after the last dose. Peaks latencies, amplitudes, and amplitude ratios were recorded. Data from the second and last BAER were compared to results at baseline. Bone conduction was performed to rule out conduction disorders. RESULTS: Seven horses had auditory loss: complete bilateral (N = 1), complete unilateral (N = 2), and partial unilateral (N = 4). Based on physical examination and BAER results, sensorineural auditory loss was suspected. Absent bone conduction ruled out a conduction disorder and further supported sensorineural auditory loss in horses with completely absent BAER. Auditory dysfunction was reversible in 4 of 7 horses. CONCLUSIONS AND CLINICAL IMPORTANCE: Gentamicin at recommended doses may cause sensorineural auditory loss in horses that might be irreversible. Follow-up studies are needed to investigate if other dosing protocols present a similar risk.

Comparison of paste and suspension formulations of omeprazole in the healing of gastric ulcers in racehorses in active training.

OBJECTIVE: To compare effects of a commercially available omeprazole paste and a compounded omeprazole suspension on healing of gastric ulcers in Thoroughbred racehorses in active training. DESIGN: Randomized controlled trial. ANIMALS: 32 horses with gastric ulcers. PROCEDURE: Horses were assigned to 2 groups on the basis of endoscopic gastric ulcer severity. Group-1 horses were treated with omeprazole suspension for 30 days and with omeprazole paste for an additional 30 days. Group-2 horses were treated with omeprazole paste for 30 days and omeprazole suspension for an additional 30 days. Serum omeprazole concentrations were measured in 4 additional healthy horses after administration of a single dose of each formulation. In all instances, omeprazole was administered at a dose of 4 mg/kg (1.8 mg/lb), p.o.. RESULTS: Ulcer severity scores on day 0 were not significantly different between groups. On day 30, ulcer severity score was significantly decreased, compared with day-0 score, in group-2 but not in group-1 horses. On day 60, ulcer severity score was significantly decreased, compared with day-0 and day-30 scores, in group-1 horses. In group-2 horses, ulcer severity score on day 60 was significantly lower than the day-0 score but was not significantly different from the day-30 score. Maximum observed serum omeprazole concentration and area under the concentration-time curve were significantly higher after administration of the paste versus the suspension formulation. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that although administration of the commercially available paste omeprazole formulation was effective in promoting healing of gastric ulcers in these horses, administration of the compounded omeprazole suspension was ineffective.