Comparison of the analgesic efficacy of hydromorphone and oxymorphone in dogs and cats: a randomized blinded study

Objective To determine if oxymorphone and hydromorphone are equally efficacious as analgesics in both dogs and cats and to determine the side-effects of each drug in painful animals. Study Design Randomized, blinded, clinical trial. Animals 151 animals (28 cats and 123 dogs) admitted to the intensive care unit requiring mu opioid agonist treatment for a variety of painful procedures. Methods Animals were randomized into two groups and received either hydromorphone or oxymorphone as their primary mu agonist agent. All staff and clinicians were blinded as to which drug was administered. Pain scores, side-effects, dose and duration were recorded for each drug dose administered. The study groups were not revealed until the study had been completed and the ensuing manuscript written. Implementation of reversal and rescue protocols were dependent on pain scores and the judgment of the primary clinician. Results The groups did not significantly differ at randomization or in the number of study drug doses. There were no statistical differences between the dose of drug or the time between each dose, indicating that potency and efficacy was not different between the two drugs. Significantly more animals that received hydromorphone vomited, but there were no other statistical differences in adverse events, or in requirement for rescue or reversal protocols. Conclusions and Clinical relevance Hydromorphone is significantly less expensive than oxymorphone and the results of this trial indicate that the two drugs have a similar clinical value. Both oxymorphone and hydromorphone can be used as primary mu agonist therapy in veterinary patients.