Retrospective Evaluation of Fluoxetine Hydrochloride Use in Horses: 95 Cases (2010-2019).

This study aimed to describe the clinical use of oral fluoxetine hydrochloride administration in horses using a retrospective medical records analysis and to determine owner perception of efficacy via a standardized questionnaire. The records of ninety-five horses for which fluoxetine had been prescribed by the equine service of a veterinary teaching hospital from November 2010 and February 2019 were identified, and data were collected from the medical records. A standardized questionnaire was used to obtain data from owners regarding length of administration, ease of administration, adverse effects, and whether the owner noted improvement in the horse's behavior. Ninety-five horses received fluoxetine during the study period. Fluoxetine was prescribed to facilitate stall rest in 68 horses (Group A) and for behavior-related problems in 27 horses (Group B). The mean dosage was 0.25 mg/kg (range 0.15-0.54). Forty-seven of the 66 owners (71%) that completed the follow-up questionnaire reported a perceived improvement in the animal's behavior (29/41 in Group A and 18/25 in Group B). Fifty-eight owners (88%) reported that they felt the medication was easy to administer. When used to facilitate extended stall confinement, fluoxetine appears to be perceived as efficacious by most owners. Although the number of behavioral cases was low, the results indicate that the drug may also be useful for some problem behaviors. Further controlled behavioral studies are needed to investigate the use of fluoxetine for equine behavioral problems.

Synovial butorphanol concentrations and mechanical nociceptive thresholds after intravenous regional limb perfusion in standing sedated horses.

OBJECTIVE: To determine synovial butorphanol concentrations and mechanical nociceptive threshold (MNT) changes after butorphanol intravenous regional limb perfusion (IVRLP). STUDY DESIGN: Experimental ANIMALS: Six adult horses. METHODS: Cephalic IVRLP was performed with 10 mg butorphanol in sedated horses with a wide rubber tourniquet and a total volume of 30 mL. Radiocarpal synovial fluid and serum concentrations along with MNT were evaluated prior to and 0.5, 1, 2, 4, and 6 hours after IVRLP. Butorphanol concentrations were determined with liquid chromatography coupled to tandem mass spectrometry positive electrospray ionization. RESULTS: Butorphanol concentrations reached mean (SD) peak concentrations of 9.47 ng/mL (±12.00) in synovial fluid and 3.89 ng/mL (3.29) in serum 30 minutes after IVRLP. Concentrations remained above baseline for 4 hours in synovial fluid (P ≤ .017) and for 2 hours in serum (P ≤ .016). The only difference in MNT was detected 1 hour after IVRLP, when MNT were higher in controls than in treated horses (P = .047). CONCLUSION: Butorphanol IVRLP seemed well tolerated and resulted in measurable levels of butorphanol in the radiocarpal synovial fluid of five of six horses. CLINICAL SIGNIFICANCE: Intravenous regional limb perfusion appears to be a viable alternative to administer butorphanol, but additional investigation is required to evaluate the dose and local concentrations required for analgesia.

Suprascapular nerve decompression for treatment of neuropathy in a bucking bull.

CASE DESCRIPTION: A 3-year-old 639-kg (1,406-lb) American bucking bull was examined because of a 4-day history of right forelimb lameness that began after the bull sustained an injury to the right shoulder region while exiting the chute during a rodeo. CLINICAL FINDINGS: A 10 × 10-cm soft tissue swelling was present over the right shoulder region. Ultrasonographically, the contour of the scapular spine, bicipital bursa, bicipital tendon, and greater tubercle of the humerus appeared unremarkable; the swelling appeared to be a hematoma overlying the distal aspect of the scapula. No external wounds, palpable joint effusion, or swellings were noted on examination of the distal portions of the limbs. The bull developed atrophy of the supraspinatus and infraspinatus muscles with lateral abduction of the shoulder joint when walking. Electromyography revealed decreased innervation to the supraspinatus and infraspinatus muscles consistent with suprascapular neuropathy. TREATMENT AND OUTCOME: The suprascapular nerve was surgically decompressed by removing the entrapping hematoma and periosteum and performing a notch resection of the scapula; dexamethasone (40 mg) was administered prior to closure. The bull was discharged 5 days after surgery; no lameness was evident at the time of discharge. The owner was instructed to restrict the bull to a stall or small pen for 6 weeks. Four months after surgery, the muscle atrophy had substantially improved, and the bull returned to bucking. CLINICAL RELEVANCE: Findings suggested that suprascapular neuropathy can develop in bulls secondary to injury and that suprascapular nerve decompression may improve nerve function, muscle atrophy, and gait.

Plasma and synovial fluid pharmacokinetics of a single intravenous dose of meropenem in adult horses.

The objective of this study was to determine the pharmacokinetics of meropenem in horses after intravenous (IV) administration. A single IV dose of meropenem was administered to six adult horses at 10 mg/kg. Plasma and synovial fluid samples were collected for 6 hr following administration. Meropenem concentrations were determined by bioassay. Plasma and synovial fluid data were analyzed by compartmental and noncompartmental pharmacokinetic methods. Mean ± SD values for elimination half-life, volume of distribution at steady-state, and clearance after IV administration for plasma samples were 0.78 ± 0.176 hr, 136.1 ± 19.69 ml/kg, and 165.2 ± 29.72 ml hr-1  kg-1 , respectively. Meropenem in synovial fluid had a slower elimination than plasma with a terminal half-life of 2.4 ± 1.16 hr. Plasma protein binding was estimated at 11%. Based on a 3-compartment open pharmacokinetic model of simultaneously fit plasma and synovial fluid, dosage simulations were performed. An intermittent dosage of meropenem at 5 mg/kg IV every 8 hr or a constant rate IV infusion at 0.5 mg/kg per hour should maintain adequate time above the MIC target of 1 µg/ml. Carbapenems are antibiotics of last resort in humans and should only be used in horses when no other antimicrobial would likely be effective.

Meropenem synovial fluid concentrations after intravenous regional limb perfusion in standing horses.

OBJECTIVE: To determine meropenem concentrations in radiocarpal (RC) joint fluid and plasma after intravenous regional limb perfusion (IVRLP). STUDY DESIGN: In vivo experimental study. ANIMALS: Nine healthy adult mares. METHODS: Meropenem (500 mg) was injected in the forelimb of standing sedated horses via IVRLP with a pneumatic tourniquet inflated to 400 mmHg. Synovial fluid was collected from RC joints at 0, 0.5, 1, 2, 4, 6, 8, 12, and 18 hours after meropenem injection. Blood samples were collected from the jugular vein at the same time points and at 5 and 15 minutes following injection. Meropenem concentrations were determined by using a microbiological bioassay. RESULTS: Median synovial fluid concentrations reached a time of maximum synovial fluid concentration 0.5 hours after IVRLP. Synovial fluid concentrations varied greatly, with a mean maximum synovial fluid concentration of 25.6 µg/mL (range, below limit of quantitation to 75.5). Concentrations remained above the breakpoint for susceptibility (1 µg/mL) for 3 hours (last nonzero concentration measured, median) and 4.1 hours (predicted, mean). Concentrations >6 µg/mL were measured for 2 hours (observed, median) and 1.7 hours (predicted, mean). Six horses had mild swelling at the injection site. CONCLUSION: Administration of 500 mg meropenem resulted in highly variable concentrations between horses and achieved levels above clinically relevant minimum inhibitory concentration for a minor portion of a once-daily dosing interval. CLINICAL SIGNIFICANCE: If time-dependent pharmacodynamics apply, IVRLP with 500 mg of meropenem may be ineffective and would likely promote resistance.