The effect of propofol administered intravenously on appetite stimulation in dogs

Anorexia is defined as diminished appetite or aversion to food. Clinical manifestations of anorexia have multiple etiologies, which include systemic illness, pain, fever, stress, metabolic disorders, and decreased palatability and learned aversion to food. Disorders of appetite are common in companion and laboratory animal medicine. Anecdotal evidence and personal experience suggest that propofol (2, 6-diisopropylphenol), when given intravenously at subhypnotic doses, causes acute appetite stimulation in dogs. The establishment of a dose-response effect could have important clinical applications; therefore, this study attempts to qualify and quantify the effect of propofol on appetite stimulation in healthy young adult dogs. Six purpose-bred male dogs (age, 6 months) were obtained from a Class A vendor. Dogs were housed individually and provided water ad libitum throughout the study period. All dogs were fed ad libitum to ensure that test conditions and degree of satiety were identical. Each dog was assigned randomly to either an experimental group or control each day of the study. The experimental groups received single bolus intravenous injections of propofol at different dosage levels (0.5, 1.0, 1.5, 2.0, or 3.0 mg/kg of body weight), and the control group received saline. The administrator was blinded to the animals identification and dose. Dosages greater than 3.0 mg/kg resulted in profound sedation and ataxia, which physically inhibited the dogs from obtaining the food; therefore 3.0 mg/kg was the highest dose tested. Dogs were weighed daily to ensure accurate dosing. Dosing was performed at the same time each day to minimize variability. Food intake amounts were recorded at 15, 30, 60, 120, and 1440 min after injection. Food intake was expressed as [food intake (g)/ body weight (kg)/ unit time (min)]. After a 1-w rest period, the study was repeated. Data were analyzed with a type RBF-65 randomized-block factoral design (ANOVA). Each dog served as its own control. The two experiments were analyzed separately, and a P-value of less than 0.05 was used to declare statistical significance. A significant (P, 0.05) increase in food consumption was observed solely during the 0-to-15-min time interval; no significant increase in food consumption was observed at any other time point. This data supports propofols appetite stimulating effect in the initial 15 min after injection. Additional studies are required to explore the mechanism for this effect and to determine whether it occurs in other species.