Pharmacokinetics of amikacin after intravenous, intra-articular, and combined intravenous and intra-articular administration in healthy neonatal foals.

BACKGROUND: Pharmacokinetics of amikacin administered IV to neonatal foals are described, but little data are available regarding the plasma concentrations contributed by concurrent intra-articular (IA) administration. HYPOTHESIS/OBJECTIVES: Compare the pharmacokinetics of amikacin when the total dose is administered IV compared to being divided between IV and IA routes of administration in neonatal foals and predict the plasma concentrations from various combined IV and IA dosing regimens. ANIMALS: Eight healthy neonatal foals. METHODS: Foals received 3 amikacin treatment protocols: (1) IV-only (25 mg/kg q24h IV), (2) concurrent IV and IA (16.7 mg/kg q24h IV and 8.3 mg/kg q24h into 1 tarsocrural joint), and (3) IA-only (8.3 mg/kg q24h into 1 tarsocrural joint). Protocols were administered for 3 days beginning at 7, 14, and 21 days of age. Plasma concentrations ≥53 µg/mL at 30 minutes were considered therapeutic for isolates with intermediate susceptibility. RESULTS: Foal age was a significant variable. The IV-only protocol met or exceeded the 30-minute plasma concentrations considered therapeutic (mean µg/mL [95% confidence interval, CI]) in 7- to 9-day-old (54.0 [52.2-56.9]), 14- to 16-day-old (58.1 [55.2-61.0]), and 21- to 23-day-old (66.6 [63.7-69.6]) foals. Concurrent IV and IA protocol did not reach the 30-minute concentration considered therapeutic in 7- to 9-day-old foals (46.5 [43.6-49.4]) but did in 14- to 16-day-old (62.9 [60.0-65.8]) and 21-to 23-day-old (62.6 [59.7-65.6]) foals. CONCLUSIONS AND CLINICAL IMPORTANCE: Concurrent IV and IA administration of amikacin produces 30-minute plasma concentrations considered therapeutic in foals 14 to 23 days old, but concentrations observed in younger foals might be below those considered therapeutic for isolates with intermediate susceptibility to amikacin.

Navicular bone fracture and severe deep digital flexor tendinopathy after palmar digital neurectomy in two horses.

Background: Navicular syndrome is a common cause of forelimb lameness in horses. Beyond changes to the navicular bone itself, horses with a clinical diagnosis of navicular syndrome often have pathology associated with other components of the navicular apparatus, including the navicular bursa, deep digital flexor (DDF) tendon, collateral sesamoidean ligaments, and impar ligament. Palmar digital neurectomy (PDN) is often used as a salvage procedure for horses diagnosed with navicular syndrome that become unresponsive to medical management. There are many potential complications associated with PDN, some of which are debilitating. Case Description: This report describes two cases of navicular bone fracture with severe DDF tendinopathy and distal interphalangeal joint subluxation/hyperextension that occurred 12 and 19 weeks after bilateral forelimb PDN. Conclusion: These two cases highlight the importance of proper patient selection before PDN due to the high incidence of undiagnosed soft tissue pathology in conjunction with radiographic evidence of navicular syndrome. Advanced imaging of the digit is recommended to identify and characterize any soft tissue pathology associated with the navicular apparatus before pursuing PDN to avoid disease progression and catastrophic injury.