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Objective—To determine the pharmacokinetics of morphine after IM administration in a clinical population of horses.

Design—Prospective clinical study.

Animals—77 horses.

Procedures—Morphine sulfate (0.1 mg/kg [0.045 mg/lb], IM) was administered to horses, and blood samples were obtained at predetermined time points. Plasma morphine concentrations were measured via liquid chromatography and mass spectrometry. In preliminary investigations, samples were obtained from 2 healthy horses at 12 time points (up to 12 hours after drug administration) and analyzed via 2-stage pharmacokinetic analysis. In the clinical phase, blood samples were obtained from 75 hospitalized horses at various times (total, 2 to 3 samples/horse) up to 9 hours after drug administration, and data were analyzed via a naïve pooled pharmacokinetic model.

Results—In the clinical phase, the apparent terminal half-life (t½) of morphine was approximately 1.5 hours, volume of distribution per bioavailability was approximately 4.5 L/kg, and clearance per bioavailability was approximately 35 mL/kg/min. Peak plasma concentration in naïve pooled analysis was 21.6 ng/mL and occurred approximately 4 minutes after administration. Morphine concentrations were below the limit of quantification ≤ 7 hours after administration in 74 horses. Adverse effects attributed to morphine administration were uncommon and considered mild.

Conclusions and Clinical Relevance—The short t½ of morphine in horses suggested frequent administration may be needed to maintain targeted plasma concentrations. Variations in plasma concentrations suggested optimal dosages may differ among horses. The drug was well tolerated at the described dose, but patients receiving morphine should be monitored carefully.

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in Journal of the American Veterinary Medical Association


Objective—To determine indications for cesarean section in alpacas and llamas, and clinical management and outcome of alpacas and llamas undergoing cesarean section.

Design—Retrospective case series.

Animals—27 alpacas and 7 llamas.

Procedures—Medical records were reviewed and information gathered on signalment, anamnesis including reproductive history, physical examination findings, indication for cesarean section, anesthetic protocol, surgical technique, number of crias delivered (alive or dead), additional treatment, duration of hospitalization, and postoperative complications. Follow-up information was gathered via email or telephone interview with owners.

Results—Uterine torsion (13/34 [38%]) was the most common reason for cesarean section. The most common surgical approach was the left proximal lateral abdominal approach (21/34 [62%]). Thirty-four crias were delivered via cesarean section. Twenty (59%) were born alive and discharged from the hospital. Retained placenta was the most common complication observed after surgery. A significant association was found between prolonged dystocia and fetal death. Of the 34 dams that underwent cesarean section, 21 were rebred, and 19 of the 21 (90.5%) dams that were rebred became pregnant. Fifteen of 19 dams were confirmed to have ≥ 1 normal vaginal delivery with a live cria following cesarean section.

Conclusions and Clinical Relevance—The results of the present study indicated that cesarean section was an effective method of resolving dystocia in camelids without negatively affecting future fertility or parturition by the dam. Prompt referral of patients with dystocia is advised to improve fetal viability. Retained fetal membranes seemed to be a common complication of cesarean section in camelids but was not associated with negative outcomes.

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in Journal of the American Veterinary Medical Association