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Objective—To determine the cardiorespiratory effects of preemptive atropine administration in dogs sedated with medetomidine.

Design—Randomized crossover trial.

Animals—12 healthy adult dogs.

Procedures—Dogs underwent 6 treatments. Each treatment consisted of administration of atropine (0.04 mg/kg [0.018 mg/lb] of body weight, IM) or saline solution (0.9% NaCl, 1 ml, IM) and administration of medetomidine (10, 20, or 40 µg/kg [4.5, 9.1, or 18.2µg/lb], IM) 10 minutes later. Treatments were administered in random order, with a minimum of 1 week between treatments. Cardiorespiratory effects before and after atropine and medetomidine administration were assessed. Duration of lateral recumbency and quality of sedation and recovery were assessed.

Results—Bradycardia (heart rate < 60 beats/min) was seen in all dogs when saline solution was administered followed by medetomidine, and the dose of medetomidine was not associated with severity or frequency of bradycardia or second-degree heart block. However, a medetomidine dose-dependent increase in mean and diastolic blood pressures was observed, regardless of whether dogs received saline solution or atropine. Preemptive atropine administration effectively prevented bradycardia and seconddegree heart block but induced pulsus alternans and hypertension. The protective effects of atropine against bradycardia lasted 50 minutes. Blood gas values were within reference limits during all treatments and were not significantly different from baseline values. Higher doses of medetomidine resulted in a longer duration of lateral recumbency.

Conclusions and Clinical Relevance—Preemptive administration of atropine in dogs sedated with medetomidine effectively prevents bradycardia for 50 minutes but induces hypertension and pulsus alternans. ( J Am Vet Med Assoc 2001;218:52–58)

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in Journal of the American Veterinary Medical Association


Objective—To determine sedative and cardiorespiratory effects of IM administration of medetomidine alone and in combination with butorphanol or ketamine in dogs.

Design—Randomized, crossover study.

Animals—6 healthy adult dogs.

Procedure—Dogs were given medetomidine alone (30 µg/kg [13.6 µg/lb] of body weight, IM), a combination of medetomidine (30 µg/kg, IM) and butorphanol (0.2 mg/kg [0.09 mg/lb], IM), or a combination of medetomidine (30 µg/kg, IM) and ketamine (3 mg/kg [1.36 mg/lb], IM). Treatments were administered in random order with a minimum of 1 week between treatments. Glycopyrrolate was given at the same time. Atipamezole (150 µg/kg [68 µg/lb], IM) was given 40 minutes after administration of medetomidine.

Results—All but 1 dog (given medetomidine alone) assumed lateral recumbency within 6 minutes after drug administration. Endotracheal intubation was significantly more difficult when dogs were given medetomidine alone than when given medetomidine and butorphanol. At all evaluation times, percentages of dogs with positive responses to tail clamping or to needle pricks in the cervical region, shoulder region, abdominal region, or hindquarters were not significantly different among drug treatments. The PaCO2 was significantly higher and the arterial pH and PaO2 were significantly lower when dogs were given medetomidine and butorphanol or medetomidine and ketamine than when they were given medetomidine alone. Recovery quality following atipamezole administration was unsatisfactory in 1 dog when given medetomidine and ketamine.

Conclusion and Clinical Relevance—Results suggested that a combination of medetomidine with butorphanol or ketamine resulted in more reliable and uniform sedation in dogs than did medetomidine alone. (J Am Vet Med Assoc 2000;216:1578–1583)

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in Journal of the American Veterinary Medical Association


Objective—To evaluate effects of medetomidine on anesthetic dose requirements, cardiorespiratory variables, plasma cortisol concentrations, and behavioral pain scores in dogs undergoing ovariohysterectomy.

Design—Randomized, prospective study.

Animals—12 healthy Walker-type hound dogs.

Procedure—Dogs received medetomidine (40 µg/kg [18.2 µg/lb] of body weight, IM; n = 6) or saline (0.9% NaCl) solution (1 ml, IM; 6) prior to anesthesia induction with thiopental; thiopental dose needed for endotracheal intubation was compared between groups. Ovariohysterectomy was performed during halothane anesthesia. Blood samples were obtained at various times before drug administration until 300 minutes after extubation. Various physiologic measurements and end-tidal halothane concentrations were recorded.

Results—In medetomidine-treated dogs, heart rate was significantly lower than in controls, and blood pressure did not change significantly from baseline. Plasma cortisol concentrations did not increase significantly until 60 minutes after extubation in medetomidine-treated dogs, whereas values in control dogs were increased from time of surgery until the end of the recording period. Control dogs had higher pain scores than treated dogs from extubation until the end of the recording period.

Conclusion and Clinical Relevance—Administration of medetomidine reduced dose requirements for thiopental and halothane and provided postoperative analgesia up to 90 minutes after extubation. Dogs undergoing ovariohysterectomy by use of thiopental induction and halothane anesthesia benefit from analgesia induced by medetomidine administered prior to anesthesia induction. Additional analgesia is appropriate 60 minutes after extubation. (J Am Vet Med Assoc 2000;217:509–514)

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in Journal of the American Veterinary Medical Association


Objective—To identify factors associated with gastrointestinal tract perforation in dogs being treated with a selective cyclooxygenase-2 (COX-2) inhibitor (deracoxib).

Design—Retrospective study.

Animals—29 dogs.

Procedure—The Novartis Animal Health pharmacovigilance database was searched for records of dogs treated with deracoxib in which gastrointestinal tract perforation was documented.

Results—16 of the 29 (55%) dogs had received deracoxib at a dosage higher than that approved by the FDA for the particular indication being treated, with 25 (86%) dogs having received deracoxib at a dosage > 2 mg/kg/d (0.9 mg/lb/d). Seventeen (59%) dogs had received at least 1 other nonsteroidal anti-inflammatory drug (NSAID) or a corticosteroid in close temporal association (within 24 hours) with deracoxib administration (ie, immediately before or following). In all, 26 (90%) dogs had received deracoxib at a higher-than-approved dosage or had received at least 1 other NSAID or corticosteroid in close temporal association with deracoxib administration. Twenty dogs died or were euthanatized, and 9 survived.

Conclusions and Clinical Relevance—In dogs with gastrointestinal tract perforation and that had been treated with deracoxib, perforation was most likely attributable to a number of factors. Deracoxib should only be used at approved dosages. Cortico-steroids and other less selective NSAIDs should not be administered in close temporal association with selective COX-2 inhibitors, including deracoxib. Further study is required to define this problem. (J Am Vet Med Assoc 2005;227:1112–1117)

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in Journal of the American Veterinary Medical Association


Objective—To determine the efficacy of long-term enalapril administration in delaying the onset of congestive heart failure (CHF).

Design—Placebo-controlled, double-blind, multicenter, randomized trial.

Animals—124 dogs with compensated mitral valve regurgitation (MR).

Procedures—Dogs randomly assigned to receive enalapril or placebo were monitored for the primary endpoint of onset of CHF for ≤ 58 months. Secondary endpoints included time from study entry to the combined endpoint of CHF-all-cause death; number of dogs free of CHF at 500, 1,000, and 1,500 days; and mean number of CHF-free days.

Results—Kaplan-Meier estimates of the effect of enalapril on the primary endpoint did not reveal a significant treatment benefit. Chronic enalapril administration did have a significant benefit on the combined endpoint of CHF-all-cause death (benefit was 317 days [10.6 months]). Dogs receiving enalapril remained free of CHF for a significantly longer time than those receiving placebo and were significantly more likely to be free of CHF at day 500 and at study end.

Conclusions and Clinical Relevance—Chronic enalapril treatment of dogs with naturally occurring, moderate to severe MR significantly delayed onset of CHF, compared with placebo, on the basis of number of CHF-free days, number of dogs free of CHF at days 500 and study end, and increased time to a combined secondary endpoint of CHF-all-cause death. Improvement in the primary endpoint, CHF-free survival, was not significant. Results suggest that enalapril modestly delays the onset of CHF in dogs with moderate to severe MR.

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in Journal of the American Veterinary Medical Association