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- Author or Editor: Ronald Gronwall x
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Summary
Each of 5 healthy mares was given 5 consecutive im injections of ceftiofur sodium (2 mg/kg of body weight; 50 mg/ml) at 12-hour intervals. Ceftiofur concentrations were measured serially in serum, synovial fluid, peritoneal fluid, and urine, and were measured in CSF and endometrial tissue after the fifth dose. Mean elimination rate constant was 0.354 ± 0.101 h−1 and elimination half-life was 2.49 ± 0.49 hour. Mean serum ceftiofur concentrations peaked approximately 1 hour after each injection. The highest mean ceftiofur concentration was 5.09 μg/ml at 1 hour after the fifth dose for serum, 3.02 μg/ml at 2 hours after the fifth dose for synovial fluid, and 3.23 μg/ml at 4 hours after the fifth dose for peritoneal fluid. Mean urine concentrations reached 15.72 μg/ml at 1 hour after the fifth dose. Ceftiofur was not detected in csf or endometrial tissue. None of the mares had adverse reactions to the drug.
Summary
Pharmacokinetic values for flunixin meglumine (1 mg/kg of body weight) and phenylbutazone (4 mg/kg) dosages were determined after a single iv injection with and without concurrent intragastric administration of probenecid (50 mg/kg) in 6 healthy mares. Significant difference was not apparent in the pharmacokinetic values of flunixin meglumine with and without concurrent probenecid administration. Significant (P ≤ 0.05) increase was evident in the 12-hour mean concentration of phenylbutazone (11.45 ± 1.66 μg/ml without probenecid; 14.56 ± 1.20 μg/ml with probenecid) along with significant (P ≤ 0.05) reduction in its volume of distribution at steady state associated with concurrent probenecid administration (218.6 ± 11.52 ml/kg without probenecid; 169.4 ± 9.25 ml/kg with probenecid).
Summary
Five healthy adult mares and 1 gelding were given a single dose (15 mg/kg of body weight) of metronidazole per rectum. After manual evacuation of feces from the rectum, a suspension of crushed tablets and water (40 ml) was administered via a 28-F catheter advanced 30 cm into the rectum. Blood samples were obtained by jugular venipuncture, and metronidazole concentration was measured serially for the 14 hours after drug administration. Mean serum concentration of metronidazole peaked at 4.5 μg/ml, 0.83 hour after administration, and decreased to 0.38 μg/ml, 14 hours after administration. Mean elimination rate constant was 0.23/h, and the harmonic mean elimination half-life was 3.04 hours. Further study is necessary to determine a therapeutic dose regimen for metronidazole administered per rectum.
Summary
Six healthy adult mixed breed dogs were each given 5 oral doses of trimethoprim (TMP)/sulfadiazine (sdz) at 2 dosage regimens: 5 mg of TMP/kg of body weight and 25 mg of SDZ/kg every 24 hours (experiment 1) and every 12 hours (experiment 2). Serum and skin concentrations of each drug were measured serially throughout each experiment and mean serum concentrations of tmp and sdz were determined for each drug for 24 hours (experiment 1) and 12 hours (experiment 2) after the last dose was given. In experiment 1, mean serum tmp concentration was 0.67 ± 0.02 μg/ml, and mean skin tmp concentration was 1.54 ± 0.40μg/g. Mean serum sdz concentration was 51.1 ± 12.2 μg/ml and mean skin sdz concentration was 59.3 ± 9.8 μg/g. In experiment 2, mean serum tmp concentration was 1.24 ± 0.35 μg/ml and mean skin tmp concentration was 3.03 ± 0.54 μg/g. Mean serum SDZ concentration was 51.6 ± 9.3 μg/ml and mean skin sdz concentration was 71.1 ± 8.2 μg/g. After the 5th oral dose in both experiments, mean concentration of tmp and sdz in serum and skin exceeded reported minimal inhibitory concentrations of tmp/sdz (≤ 0.25/4.75 μg/ml) for coaguase-positive Staphylococcus sp. It was concluded that therapeutically effective concentrations in serum and skin were achieved and maintained when using the manufacturer’s recommended dosage of 30 mg of tmp/sdz/kg (5 mg of TMP/kg and 25 mg of sdz/kg) every 24 hours.
SUMMARY
Serum concentrations of metronidazole were determined in 6 healthy adult mares after a single iv injection of metronidazole (15 mg/kg of body weight). The mean elimination rate (K) was 0.23 h-1, and the mean elimination half-life (t1/2) was 3.1 hours. The apparent volume of distribution at steady state was 0.69 L/kg, and the clearance was 168 ml/h/kg.
Each mare was then given a loading dose (15 mg/kg) of metronidazole at time 0, followed by 4 maintenance doses (7.5 mg/kg, q 6 h) by nasogastric tube. Metronidazole concentrations were measured in serial samples of serum, synovia, peritoneal fluid, and urine. Metronidazole concentrations in csf and endometrial tissues were measured after the fourth maintenance dose. The highest mean concentration in serum was 13.9 ± 2.18 μg/ml at 40 minutes after the loading dose (time 0). The highest mean synovial and peritoneal fluid concentrations were 8.9 ± 1.31 μg/ml and 12.8 ± 3.21 μg/ml, respectively, 2 hours after the loading dose. The lowest mean trough concentration in urine was 32 μg/ml. Mean concentration of metronidazole in csf was 4.3 ± 2.51 μg/ml and the mean concentration in endometrial tissues was 0.9 ± 0.48 μg/g at 3 hours after the fourth maintenance dose.
Two mares hospitalized for treatment of bacterial pleuropneumonia were given metronidazole (15.0 mg/kg, po, initially then 7.5 mg/kg, po, q 6 h), while concurrently receiving gentamicin, potassium penicillin, and flunixin meglumine iv. Metronidazole pharmacokinetics and serum concentrations in the sick mares were similar to those obtained in the healthy mares.
Summary
Six calves with suppurative arthritis were given a single im injection of sodium cephapirin at a dosage of 10 mg/kg of body weight. Cephapirin concentrations were serially measured in serum and in normal and suppurative synovial fluid over a 24-hour period. Mean peak serum concentration was 6.33 μl/ml at 20 minutes after injection. The highest cephapirin concentrations in normal and suppurative synovial fluid were 1.68 and 1.96 μg/ml, respectively, 30 minutes after injection. Overall mean cephapirin concentration in normal synovial fluid for the first 4 hours (1.04 ± 0.612 μg/ml) was not significantly different from that in suppurative synovial fluid (0.88 ± 0.495 μg/ml; P > 0.05). Elimination half-life was 0.60 hours and clearance was 1,593 ml/h/kg.