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To evaluate distribution and intensity of 99mTc-methylene diphosphonate (99mTc-MDP) uptake in the navicular area in horses with forelimb lameness isolated to the palmar aspect of the foot.


Prospective, case-controlled study.


7 horses with clinical signs of navicular syndrome and 7 control horses.


Palmar view, soft tissue-phase scintigraphic images of the foot were obtained between 7 and 12 minutes after injection of 120 to 170 mCi of 99mTc-MDP. Lateral and palmar view, bone-phase images were obtained at 30 minutes and 1, 2, and 4 hours after injection. Palmar views were evaluated by determining the ratio of image density in the navicular area to mean image density in the distal phalangeal area. Palmar and lateral view, bone-phase images were also scored on the basis of navicular area intensity (intense = 3, moderate = 2, mild = 1, and no uptake = 0). Density ratios and mean scores were evaluated as a three-way ANOVA.


Mean navicular-to-distal phalangeal density ratio for affected horses (1.77) was significantly (P = 0.003) greater than that for control horses (0.97). The mean subjective score for affected horses when evaluating palmar views only (1.85) and when evaluating palmar and lateral view pairs together (1.99) was significantly (P < 0.01) higher than scores for control horses (0.51, 0.62). Images obtained 1 hour after injection were as good at differentiating affected from control horses as images obtained between 2 to 4 hours after injection.


A substantial number of horses with palmar foot pain have increased scintigraphic uptake within the navicular bone 1 to 4 hours after injection of 99mTc-MDP. Lateral view, bone-phase images are less sensitive than palmar view, bone-phase images in revealing navicular area uptake.

Clinical Relevance

A combination of lateral and palmar view scintigraphic images obtained between 1 and 4 hours after injection of 99mTc-MDP is a useful diagnostic aid in evaluating navicular bone involvement in horses with forelimb lameness isolated to the palmar aspect of the foot. (Am J Vet Res 1996;57:415–421)

Free access
in American Journal of Veterinary Research


A commercially available automated enzyme-multiplied immunoassay technique (emit) was used to determine serum caffeine concentration after oral and iv administrations of caffeine at dosage of 5 mg/kg of body weight to 12 clinically normal dogs. Dogs were allotted to 2 groups of 6 dogs each; 1 group initially received caffeine orally and the other received caffeine iv. After 72 hours, caffeine administration was repeated in all dogs in the alternate manner. Serum samples were obtained at multiple intervals over 24 hours to determine distribution and elimination kinetics. Analysis of the drug concentration-time data indicated iv elimination half-life (t½) of 6.39 ± 1.87 hours, volume of distribution at steady state of 685.3 ± 132.2 ml/kg, total body clearance of 1.31 ± 0.38 ml/min/kg, absorption t½ of 1.02 ± 0.68 hour, oral elimination t½ of 6.53 ± 2.72 hours, lag time after oral administration of 0.0614 ± 0.0661 hour, highest measured concentration of 5.29 ± 1.17 μg/ml, time to peak concentration of 2.74 ± 1.30 hours, and bioavailability of 99.4 ± 19.4%. Data from 6 dogs best fit a 1-compartment open model and those from 6 other dogs best fit a 2-compartment open model. On the basis of data from the 6 dogs that best fit a 2-compartment model, t½ of distribution was 0.58 ± 0.72 hour. Data for oral administration best fit a single absorption phase and a single elimination phase.

The increased availability and simplicity of the emit offers an opportunity to study the application of caffeine elimination for clinical evaluation of dogs with liver disease. Data obtained from this study allow determination of t½ and clearance to be simplified by obtaining samples 4 and 8 hours after oral or iv administrations and establishes canine reference values for elimination kinetics of caffeine administered at dosage of 5 mg/kg and assayed by use of the emit.

Free access
in American Journal of Veterinary Research


Eight Holstein cows, 4 inoculated intracistemally in 1 quarter of the mammary gland with Escherichia coli and 4 noninfected controls, were administered ceftiofur sodium (3 mg/kg of body weight, IV, q 12 hours) for 24 hours, beginning at 14 hours after inoculation of infected cows. All challenge-exposed cows became infected, with mean ± SEM peak log10 bacterial concentration in milk of 5.03 ± 0.69 colonyforming units/ml. The infection resulted in systemic signs (mean peak rectal temperature, 41.5 ± 0.3 C; anorexia; signs of depression) and local inflammation (mean peak albumin concentration in milk, 7.89 ± 1.71 mg/ml). Ceftiofur was detectable in milk from all challenge-exposed cows, compared with only 1 of 4 noninfected cows, and the mean period after inoculation that ceftiofur was detectable in milk was longer (P < 0.05) in infected (147.7 ± 27.5 hours) than noninfected cows (1.3 ± 1.3 hours). However, maximal ceftiofur concentration attained in milk for all cows was 0.28 p.g/ml, and was 0.20 jig/ml or less for all but 2 milk samples collected for 10 days after challenge exposure. Mean serum concentration of ceftiofur peaked at 1.0 ± 0.3 μg/ml and 0.7 ± 0.1 μg/ml for infected and noninfected cows, respectively. After each ceftiofur dose, mean peak and trough concentrations of ceftiofur in serum did not differ between groups; however, concentration of ceftiofur in serum was higher at 7 hours after each dose in noninfected cows, suggesting more rapid clearance of the drug in infected cows. Ceftiofur was not detected in serum (< 0.05 μg/ml) of any cow at or after 120 hours following inoculation of infected cows.

Storage of serum samples at —20 C for 3 weeks resulted in a 98.8% decrease in ceftiofur activity, compared with that in fresh serum samples. Eightyseven percent of this loss occurred 30 minutes after mixing serum and ceftiofur; thus, about 13% of the original activity was lost in storage. Storage of milk samples under similar conditions did not result in loss of ceftiofur activity.

Despite acute inflammation, the dosage of ceftiofur used in this trial would not result in drug concentrations in milk above FDA safe concentrations, or above the reported minimum inhibitory concentration for coliform bacteria.

Free access
in American Journal of Veterinary Research


The adverse effects of administration of gentamicin (5 mg/kg of body weight, im, q 12 h) for 7 days were studied in healthy scarlet macaws (Ara macao) and galahs (Eolophus roseicapillus; cockatoos). Polydipsia and polyuria developed in each species, but were greater and persisted longer in the cockatoos. Peak water intake in the cockatoos more than quadrupled, and remained increased for 23 days after cessation of gentamicin administration. Plasma aspartate transaminase activity increased significantly (P < 0.05) after treatment in the macaws, and plasma aspartate transaminase and lactate dehydrogenase activities increased in the cockatoos.

Single im administration of gentamicin (5 mg/kg) resulted in mean (± sem) plasma concentration of 20.6 (± 1.85) μg/ml at 0.5 hour for either species of birds. There were no significant differences between mean plasma gentamicin concentrations for cockatoos and macaws at any time after drug administration, except at 12 hours, when values for cockatoos were significantly (P < 0.05) greater than those for macaws. The elimination half-life for gentamicin after im administration of 5 and 10 mg/kg was 1.17 and 1.07 hours, respectively, for macaws and 1.23 and 1.44 hours, respectively, for cockatoos. Correlation between drug disposition and adverse side effects could not be detected.

Free access
in American Journal of Veterinary Research