Effects of three acepromazine doses on the incidence of morphine-induced vomiting, sedation and some physiological variables in dogs

Background: Acepromazine was found to reduce the incidence of vomiting induced by opioids such as morphine, hydromorphone and oxymorphone in dogs. Despite the effectiveness of the phenothiazine in preventing opioid-induced vomiting in this species, a single dose of acepromazine (0.05 mg/kg) was tested and the influence of dose on the antiemetic effect of the drug is unknown. The primary objective of this study was to evaluate the effect of three acepromazine doses on the incidence of vomiting induced by morphine in dogs. A secondary aim was to assess the degree of sedation and effects on physiological variables following administration of the combinations tested. Materials, Methods & Results: All dogs received 0.5 mg/kg morphine (IM). Fifteen min before morphine, dogs in the Control, ACPLD, ACPMD and ACPHD groups were administered (IM) physiological saline or acepromazine at doses of 0.025, 0.05 and 0.1 mg/kg, respectively. In Phase 1, purpose-bred dogs (n = 8) underwent each of the four treatments in a randomized, crossover design; the incidence of vomiting, sedation, pulse rate (PR), systolic, mean and diastolic blood pressures (SAP, MAP and DAP) were investigated for 60 min. Sedation was assessed by a numeric descriptive scale (NDS, range 0-3) and a simple numerical scale (SNS, range 1-10). In Phase 2, client-owned dogs (n = 50) received a single treatment and only the incidence of vomiting was assessed. There was no significant difference between groups on the incidence of vomiting recorded in Phase 1, Phase 2 and the average of Phases 1 and 2. A significant decrease in PR was observed in most groups but no significant difference was detected between groups. Blood pressure decreased in all groups; during most of the evaluation period, SAP, MAP and DAP were significantly higher in the Control than in other treatments. Dogs in this study presented mild to intense sedation. A significant difference in NDS scores was observed between the Control and ACPMD groups whereas for SNS scores, significant differences were detected between the ACPMD and ACPHD groups compared with the Control group. The number of dogs presenting intense sedation as judged by the NDS (NDS score = 3) were: 1/8, 3/8, 3/8 and 4/8 dogs in the Control, ACPLD, ACPMD and ACPHD groups, respectively. Discussion: The hypothesis of the study was rejected. The acepromazine dose did not influence the frequency of morphineinduced vomiting, the degree of sedation or cardiovascular variables after administration of either treatment. The frequency of vomiting was high (≥ 75%) in dogs of the present study regardless of the treatment administered. There was no significant difference in the frequency of vomiting in ACPLD, ACPMD and ACPHD as compared to the Control group. This finding was unexpected because it has been reported in a previous study that acepromazine reduced the incidence of opioid-induced vomiting in dogs. ACPLD, ACPMD and ACPHD improved the quality of sedation compared to the Control treatment but no significant difference in sedation scores was observed among these groups. These findings suggest that, when combined to morphine, there is no improvement in sedation when the acepromazine dose is increased above 0.025 mg/kg in dogs.Despite a significant decrease, mean values of PR, SAP, MAP and DAP remained within the physiological range for conscious dogs. In summary, none of the acepromazine doses was effective in preventing morphine-induced vomiting in dogs. Sedation is greater after acepromazine-morphine combinations than after morphine alone and is not influenced by the acepromazine dose. Cardiovascular effects induced by combinations administered in this study were well tolerated and of little clinical relevance to healthy conscious dogs

Effects of three acepromazine doses on the incidence of morphine-induced vomiting, sedation and some physiological variables in dogs

Background: Acepromazine was found to reduce the incidence of vomiting induced by opioids such as morphine, hydromorphone and oxymorphone in dogs. Despite the effectiveness of the phenothiazine in preventing opioid-induced vomiting in this species, a single dose of acepromazine (0.05 mg/kg) was tested and the influence of dose on the antiemetic effect of the drug is unknown. The primary objective of this study was to evaluate the effect of three acepromazine doses on the incidence of vomiting induced by morphine in dogs. A secondary aim was to assess the degree of sedation and effects on physiological variables following administration of the combinations tested. Materials, Methods & Results: All dogs received 0.5 mg/kg morphine (IM). Fifteen min before morphine, dogs in the Control, ACPLD, ACPMD and ACPHD groups were administered (IM) physiological saline or acepromazine at doses of 0.025, 0.05 and 0.1 mg/kg, respectively. In Phase 1, purpose-bred dogs (n = 8) underwent each of the four treatments in a randomized, crossover design; the incidence of vomiting, sedation, pulse rate (PR), systolic, mean and diastolic blood pressures (SAP, MAP and DAP) were investigated for 60 min. Sedation was assessed by a numeric descriptive scale (NDS, range 0-3) and a simple numerical scale (SNS, range 1-10). In Phase 2, client-owned dogs (n = 50) received a single treatment and only the incidence of vomiting was assessed. There was no significant difference between groups on the incidence of vomiting recorded in Phase 1, Phase 2 and the average of Phases 1 and 2. A significant decrease in PR was observed in most groups but no significant difference was detected between groups. Blood pressure decreased in all groups; during most of the evaluation period, SAP, MAP and DAP were significantly higher in the Control than in other treatments. Dogs in this study presented mild to intense sedation. A significant difference in NDS scores was observed between the Control and ACPMD groups whereas for SNS scores, significant differences were detected between the ACPMD and ACPHD groups compared with the Control group. The number of dogs presenting intense sedation as judged by the NDS (NDS score = 3) were: 1/8, 3/8, 3/8 and 4/8 dogs in the Control, ACPLD, ACPMD and ACPHD groups, respectively. Discussion: The hypothesis of the study was rejected. The acepromazine dose did not influence the frequency of morphineinduced vomiting, the degree of sedation or cardiovascular variables after administration of either treatment. The frequency of vomiting was high (≥ 75%) in dogs of the present study regardless of the treatment administered. There was no significant difference in the frequency of vomiting in ACPLD, ACPMD and ACPHD as compared to the Control group. This finding was unexpected because it has been reported in a previous study that acepromazine reduced the incidence of opioid-induced vomiting in dogs. ACPLD, ACPMD and ACPHD improved the quality of sedation compared to the Control treatment but no significant difference in sedation scores was observed among these groups. These findings suggest that, when combined to morphine, there is no improvement in sedation when the acepromazine dose is increased above 0.025 mg/kg in dogs.Despite a significant decrease, mean values of PR, SAP, MAP and DAP remained within the physiological range for conscious dogs. In summary, none of the acepromazine doses was effective in preventing morphine-induced vomiting in dogs. Sedation is greater after acepromazine-morphine combinations than after morphine alone and is not influenced by the acepromazine dose. Cardiovascular effects induced by combinations administered in this study were well tolerated and of little clinical relevance to healthy conscious dogs

Influence of acepromazine on the cardiovascular actions of dobutamine in isoflurane-anesthetized horses Influência da acepromazina sobre os efeitos cardiovasculares da dobutamina em cavalos anestesiados com isofluorano

The influence of acepromazine (ACP) on the effectiveness of dobutamine (DBT) in increasing blood pressure during isoflurane (ISO) anesthesia was evaluated in six horses. On separate occasions, the horses were randomly assigned to receive NaCl 0.9% (Control), ACP 0.025mg kg-1 and ACP 0.05mg kg-1. The experimental treatment was administered prior to induction of anesthesia. Maintenance of anesthesia was performed under conditions of normocapnia with ISO in oxygen. Dobutamine was administered at progressively increasing infusion rates until mean arterial pressure (MAP) reached 70mmHg or until a maximum infusion rate of 5.0µg kg-1 min-1. Compared with baseline, DBT increased heart rate, systolic, diastolic and mean blood pressures in all treatments. However, these variables did not differ among treatments. The target MAP (70mmHg) was not reached in 2/6, 2/5 and 0/6 horses in the Control, ACP0.025 and ACP0.05 treatments, respectively. The mean dose of DBT to achieve target MAP was 3.5±1.8, 3.7±1.6 and 2.7±1.4µg kg-1 min-1 in the Control, ACP0.025 and ACP0.05 treatments, respectively (P>0.05). Under the conditions of this study, premedication with ACP does not interfere with the effectiveness of DBT in increasing blood pressure in horses anesthetized with ISO.A influência da acepromazina (ACP) sobre a capacidade da dobutamina (DBT) em elevar a pressão arterial durante a anestesia com isofluorano (ISO) foi avaliada em seis equinos. Em ocasiões diferentes, os animais receberam aleatoriamente NaCl 0,9% (Controle), ACP 0,025mg kg-1 e ACP 0,05mg kg-1. O tratamento experimental foi administrado previamente à indução da anestesia. A manutenção da anestesia foi realizada em condições de normocapnia com ISO em oxigênio. A administração de DBT foi iniciada em doses progressivamente crescentes até que o valor de pressão arterial média (PAM) atingisse 70mmHg ou até a dose máxima de 5,0µg kg-1 min-1. Comparado ao basal, a administração da DBT resultou em elevação na frequência cardíaca e pressões arteriais sistólica, diastólica e média em todos os tratamentos. Porém, não houve diferença entre os tratamentos nessas variáveis. A PAM alvo (70mmHg) não foi atingida em 2/6, 2/5 e 0/6 animais dos tratamentos Controle, ACP0.025 e ACP0.05, respectivamente. A dose média de DBT para a PAM alvo foi de 3,5±1,8; 3,7±1,6 e 2,7±1,4µg kg-1 min-1 no Controle, ACP0.025 e ACP0.05, respectivamente (P>0,05). Nas condições deste estudo, o pré-tratamento com ACP não interfere na eficácia da DBT em elevar a pressão arterial de cavalos anestesiados com ISO