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Abstract

Objective—To assess kinetic 2-([18F]fluoro)-2-deoxy-d-glucose (18FDG) uptake in the brain of anesthetized healthy adult dogs by use of positron emission tomography (PET) and to determine whether 18FDG uptake differs among anatomic regions of the brain.

Animals—5 healthy Beagles.

Procedures—Each isoflurane-anesthetized dog was administered 18FDG IV (dose range, 3.0 to 5.2 mCi), and PET data were acquired for 2 hours. A CT scan (without contrast agent administration) was performed to allow more precise neuroanatomic localization. Defined regions of interest within the brain were drawn on reconstructed image data. Standard uptake values (SUVs) for 18FDG were calculated to generate time-activity curves and determine time to peak uptake.

Results—Time-activity curve analysis identified 4 regional uptake patterns: olfactory, gray matter, white matter, and other (brainstem, cerebellum, and occipital and frontal regions). The highest maximum SUVs were identified in the olfactory bulbs and cerebral gray matter, and the lowest maximum SUV was identified in cerebral white matter. Mean time to peak uptake ranged from 37.8 minutes in white matter to 82.7 minutes in the olfactory bulbs.

Conclusions and Clinical Relevance—Kinetic analysis of 18FDG uptake revealed differences in uptake values among anatomic areas of the brain in dogs. These data provide a baseline for further investigation of 18FDG uptake in dogs with immune-mediated inflammatory brain disease and suggest that 18FDG-PET scanning has potential use for antemortem diagnosis without histologic analysis and for monitoring response to treatment. In clinical cases, a 1-hour period of PET scanning should provide sufficient pertinent data.

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE To evaluate the pharmacokinetics of zonisamide following rectal administration of 20 or 30 mg/kg suspended in sterile water or polyethylene glycol (PEG) to healthy dogs and determine whether either dose resulted in plasma zonisamide concentrations within the recommended therapeutic target range (10 to 40 μg/mL).

ANIMALS 8 healthy mixed-breed dogs.

PROCEDURES Each dog received each of 2 doses (20 or 30 mg/kg) of zonisamide suspended in each of 2 delivery substrates (sterile water or PEG) in a randomized crossover study with a 7-day washout period between phases. A blood sample was collected from each dog immediately before and at predetermined times for 48 hours after zonisamide administration. Plasma zonisamide concentrations were determined by high-performance liquid chromatography, and data were analyzed with a noncompartmental model.

RESULTS Mean maximum plasma concentration, time to maximum plasma concentration, mean residence time, and elimination half-life did not differ significantly among the 4 treatments. The mean maximum plasma concentration for all 4 treatments was less than the therapeutic target range. The mean ± SD area under the concentration-time curve for the 30 mg/kg-in-water treatment (391.94 ± 237.00 h•μg/mL) was significantly greater than that for the 20 mg/kg-in-water (146.19 ± 66.27 h•μg/mL) and 20 mg/kg-in-PEG (87.09 ± 96.87 h•μg/mL) treatments.

CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that rectal administration of zonisamide at doses of 20 and 30 mg/kg failed to achieve plasma zonisamide concentrations within the recommended therapeutic target range. Therefore, rectal administration of zonisamide cannot be recommended as a suitable alternative to oral administration.

Full access
in American Journal of Veterinary Research