EFFECTS OF MEDETOMIDINE ON SERUM OSMOLALITY - URINE VOLUME, OSMOLALITY AND PH - FREE-WATER CLEARANCE - AND FRACTIONAL CLEARANCE OF SODIUM, CHLORIDE, POTASSIUM, AND GLUCOSE IN DOGS

Objective-To determine effects of IV medetomidine administration on se lected clinicopathologic variables in dogs. Animals-6 healthy adult Be agles. Procedure-Dogs were randomly assigned to each of 3 treatments i n a crossover study design. Serum osmolality, urine osmolality, urine pH, and fractional clearances of sodium, chloride, potassium, and gluc ose were determined before and 20, 40, 60, 120, 180, 240, 300, 360, 42 0, and 480 minutes after IV administration of 0.9% NaCl (saline) solut ion (control) or medetomidine (10 or 20 mu g/kg of body weight). The u rinary bladder was emptied prior to saline or medetomidine administrat ion, and urine volume was determined at the same posttreatment times a s those described previously. Free water clearance was calculated for all posttreatment times. Results-After medetomidine administration, se rum osmolality, urine volume, free water clearance, and fractional cle arance of potassium and glucose increased; urine osmolality decreased. Initially, urine pH and fractional clearance of chloride decreased, t hen subsequently increased. Fractional clearance of sodium did not cha nge. Conclusions and Clinical Relevance-Because IV administration of m edetomidine to dogs at dosages of 10 and 20 mu g/kg induces a diuretic effect that lasts up to 4 hours, the drug should be used with discret ion in hypovolemic or dehydrated dogs, and its use should be avoided i n those with urinary tract obstruction.