RESUMO
OBJECTIVE: To evaluate the post-operative analgesic effect of metamizol (dipyrone) administered intravenously at three different doses (15 mg kg(-1), 25 mg kg(-1) and 35 mg kg(-1)) compared to placebo in dogs undergoing ovariohysterectomy. STUDY DESIGN: Prospective, comparative, randomized, blinded trial. ANIMALS: Forty healthy bitches, aged 1-6 years, weighing 10-35 kg METHODS: The animals were randomly divided into four groups and received their respective treatments immediately after surgery: placebo group (0.9% saline solution), D15 group (metamizol 15 mg kg(-1) IV), D25 group (metamizol 25 mg kg(-1) IV), D35 group (metamizol 35 mg kg(-1) IV). The following variables were measured: sedation, pulse rate (PR), respiratory rate (f(R)), arterial blood pressure (ABP), plasma catecholamines, serum cortisol, blood urea nitrogen (BUN) and creatinine metabolites, albumin, alanine aminotransferase (ALT), alkaline phosphatase (ALP), hemogram, platelet counts and level of analgesia which was assessed by visual analog (VAS), descriptive and behavioral scales. Patients were monitored for 48 hours after the administration of the analgesic agent. Rescue analgesia (tramadol, 2 mg kg(-1), intramuscularly) was provided for animals with pain scores ≥4, as determined by the VAS or descriptive scale. RESULTS: The D25 and D35 groups showed equivalent post-operative analgesia, as shown by decreased pain scores, according to the three different pain scales, and fewer animals that required rescue analgesia. Significantly lower serum cortisol concentrations were observed in the D25 and D35 groups when compared to the placebo and D15 groups. No hematologic, renal, hepatic or clinical adverse effects were observed during the treatment. CONCLUSIONS AND CLINICAL RELEVANCE: Metamizol administered intravenously at 25 or 35 mg kg(-1) can provide adequate post-operative analgesia in bitches undergoing ovariohysterectomy.