Objective—To determine the pharmacokinetics of
acetazolamide administered IV and orally to horses.
Animals—6 clinically normal adult horses.
Procedure—Horses received 2 doses of acetazolamide
(4 mg/kg of body weight, IV; 8 mg/kg, PO), and
blood samples were collected at regular intervals
before and after administration. Samples were
assayed for acetazolamide concentration by high-performance
liquid chromatography, and concentrationtime
data were analyzed.
Results—After IV administration of acetazolamide,
data analysis revealed a median mean residence time
of 1.71 ± 0.90 hours and median total body clearance
of 263 ± 38 ml/kg/h. Median steady-state volume of
distribution was 433 ± 218 ml/kg. After oral administration,
mean peak plasma concentration was 1.90 ±
1.09 µg/ml. Mean time to peak plasma concentration
was 1.61 ± 1.24 hours. Median oral bioavailability was
25 ± 6%.
Conclusions and Clinical Relevance—Oral pharmacokinetic
disposition of acetazolamide in horses was characterized
by rapid absorption, low bioavailability, and
slower elimination than observed initially after IV administration.
Pharmacokinetic data generated by this study
should facilitate estimation of appropriate dosages for
acetazolamide use in horses with hyperkalemic periodic
paralysis. (Am J Vet Res 2000;61:965–968)
Objective—To evaluate the musculoskeletal analgesic effect of etodolac administered PO every 12 or 24 hours in chronically lame horses by use of force plate analysis.
Animals—22 horses with navicular syndrome.
Procedure—Horses received etodolac (23 mg/kg, PO, q 12 h; n = 7), etodolac (23 mg/kg, PO, q 24 h; 8), or corn syrup (20 mL, PO, q 24 h; control treatment; 7) for 3 days. Combined forelimb peak vertical ground reaction force (PVF) was measured via force plate analysis before the first treatment (baseline) and at 6, 12, 24, and 36 hours after the last treatment. Differences in mean PVF (mPVF) between baseline and subsequent measurements were analyzed (repeated-measures ANOVA) and evaluated for treatment and time effects and treatment-time interaction.
Results—Once- or twice-daily administration of etodolac resulted in significant increases in mPVF from baseline at 6, 12, and 24 hours after the last treatment, compared with the control treatment. There were no significant differences in mPVF between the etodolac treatment groups at any time point. In both etodolac treatment groups, there was a significant increase in mPVF from baseline at 6, 12, and 24 hours, compared with that at 36 hours. Etodolac-associated adverse effects were not detected.
Conclusions and Clinical Relevance—In horses with navicular syndrome, once-daily oral administration of 23 mg of etodolac/kg appears to provide effective analgesia for as long as 24 hours. Twice-daily administration of etodolac at this same dose does not appear to provide any additional analgesic efficacy or duration of effect.
Objective—To use force plate analysis to evaluate the
analgesic efficacies of flunixin meglumine and
phenylbutazone administered IV at typical clinical
doses in horses with navicular syndrome.
Animals—12 horses with navicular syndrome that
were otherwise clinically normal.
Procedure—Horses received flunixin (1.1 mg/kg),
phenylbutazone (4.4 mg/kg), or physiologic saline
(0.9% NaCl; 1 mL/45 kg) solution administered IV
once daily for 4 days with a 14-day washout period
between treatments (3 treatments/horse). Before
beginning treatment (baseline) and 6, 12, 24, and 30
hours after the fourth dose of each treatment, horses
were evaluated by use of the American Association of
Equine Practitioners lameness scoring system (half
scores permitted) and peak vertical force of the forelimbs
was measured via a force plate.
Results—At 6, 12, and 24 hours after the fourth treatment,
subjective lameness evaluations and force
plate data indicated significant improvement in lameness
from baseline values in horses treated with flunixin
or phenylbutazone, compared with control horses;
at those time points, the assessed variables in flunixin-
or phenylbutazone-treated horses were not significantly
Conclusions and Clinical Relevance—In horses
with navicular syndrome treated once daily for 4 days,
typical clinical doses of flunixin and phenylbutazone
resulted in similar significant improvement in lameness
at 6, 12, and 24 hours after the final dose, compared
with findings in horses treated with saline solution.
The effect of flunixin or phenylbutazone was
maintained for at least 24 hours. Flunixin meglumine
and phenylbutazone appear to have similar analgesic
effects in horses with navicular syndrome. (Am J Vet
Objective—To compare analgesic effects of phenylbutazone
administered at a dosage of 4.4 mg/kg/d
(2 mg/lb/d) or 8.8 mg/kg/d (4 mg/lb/d) in horses with
Design—Controlled crossover study.
Animals—9 horses with chronic forelimb lameness.
Procedure—Horses were treated IV with phenylbutazone
(4.4 mg/kg/d or 8.8 mg/kg/d) or saline (0.9%
NaCl) solution once daily for 4 days. All horses
received all 3 treatments with a minimum of 14 days
between treatments. Mean peak vertical force (mPVF)
was measured and clinical lameness scores were
assigned before initiation of each treatment and 6, 12,
and 24 hours after the final dose for each treatment.
Results—Compared with values obtained after
administration of saline solution, mPVF was significantly
increased at all posttreatment evaluation times
when phenylbutazone was administered. Clinical
lameness scores were significantly decreased 6 and
12 hours after administration of the final dose when
phenylbutazone was administered at the low or high
dosage but were significantly decreased 24 hours
after treatment only when phenylbutazone was
administered at the high dosage. No significant differences
in mPVF and clinical lameness scores were
found at any time when phenylbutazone was administered
at the low versus high dosage.
Conclusions and Clinical Relevance—Results suggest
that the high dosage of phenylbutazone was not
associated with greater analgesic effects, in terms of
mPVF or lameness score, than was the low dosage.
Considering that toxicity of phenylbutazone is related
to dosage, the higher dosage may not be beneficial in
chronically lame horses. (J Am Vet Med Assoc 2005;226:414–417)
Objective—To assess the analytic sensitivity of an inertial sensor system for detection of the more severely affected forelimb in horses with bilateral lameness.
Animals—18 adult horses with forelimb lameness.
Procedures—Horses were fitted with inertial sensors and evaluated for lameness with a stationary force plate as they were trotted in a straight line. Inertial sensor-derived measurements for vertical head movement asymmetry (HMA) and vector sum (VS) of maximum and minimum head height differences between right and left halves of the stride were used to predict differences in mean peak vertical force (PVF) as a percentage of body weight between the right and left forelimbs. Repeatability was compared by calculation of the intraclass correlation coefficient (ICC) for each variable. Correct classification percentages for the lamer forelimb were determined by use of a stationary force plate as the standard.
Results—SEs of the prediction of difference in PVF between the right and left forelimbs from HMA and VS were 6.1% and 5.2%, respectively. Head movement asymmetry (ICC, 0.72) was less repeatable than PVF (ICC, 0.86) and VS (ICC, 0.84). Associations were positive and significant between HMA (R2 = 0.73) and VS (R2 = 0.81) and the difference in PVF between the right and left forelimbs. Correct classification percentages for HMA and VS for detecting the lamer forelimb were 83.3% and 77.8%, respectively.
Conclusions and Clinical Relevance—Results suggested that an inertial sensor system to measure vertical asymmetry (HMA and VS) due to forelimb lameness in horses trotting in a straight line has adequate analytic sensitivity for clinical use. Additional studies are required to assess specificity of the system.