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Biomedical subjects

C G MacAllister

Publications and source records attributed to C G MacAllister.

31 records · Page 2Linked to original sources
PubMed1992

Rifampin disposition in the horse: effects of age and method of oral administration.

The effects of time and method of administration of rifampin with respect to feeding were evaluated in five mature horses. There was a significant (P less than or equal to 0.05) delay in time of maximum serum concentration and an apparent but not significant decrease in oral absorption when rifampin was given as a top dressing on grain as compared with administration in corn syrup 2 h before or 2 h after feeding. Although there were no differences between administration before or after feeding, administration 2 h prior to feeding was selected as the method of choice for future experiments. The effects of age on rifampin disposition were subsequently examined using this method of administration in six, 1-week old foals. Rifampin (10 mg/kg) was given at increasing age from 1 through 10 weeks and the pharmacokinetic disposition parameters compared. There were significant differences in the slope of the elimination phase (beta) and area under the curve (AUC) at 1 week through 6 weeks compared with 10 weeks or with values in the five mature horses.

Administration, Oral↗
PubMed1992

Pharmacokinetics of intravenously and orally administered pyrimethamine in horses.

Single-dose pharmacokinetic variables of pyrimethamine were studied in horses. Pyrimethamine (1 mg/kg of body weight) was administered IV and orally to 6 adult horses, and plasma samples were obtained at frequent intervals thereafter. Plasma pyrimethamine concentration was assayed by gas chromatography, and concentration-time data were analyzed, using a pharmacokinetic computer program. The IV and oral administration data were best described by 3-compartment and 1-compartment models, respectively. The median volume of distribution at steady state after IV administration was 1,521 ml/kg and the median elimination half-time was 12.06 hours. Mean plasma concentration after oral administration fluctuated between a maximal concentration of 0.18 microgram/ml and 0.09 microgram/ml (24 hours after dosing). Bioavailability after oral administration was 56%.

Administration, Oral↗
PubMed1992

Pharmacokinetics, penetration into cerebrospinal fluid, and hematologic effects after multiple oral administrations of pyrimethamine to horses.

Pharmacokinetics, CSF penetration, and hematologic effects of oral administration of pyrimethamine were studied after multiple dosing. Pyrimethamine (1 mg/kg of body weight) was administered orally once a day for 10 days to 5 adult horses, and blood samples were collected frequently after the first, fifth, and tenth doses. The CSF samples were obtained by cisternal puncture 4 to 6 hours after administration of the first, third, seventh, and tenth doses. Pyrimethamine concentration in plasma and CSF was quantified by gas chromatography, and plasma concentration-time data were analyzed, using a pharmacokinetic computer program. Repeated daily dosing resulted in accumulation of pyrimethamine in plasma, with steady state being achieved within 5 days, when the mean peak plasma concentration was more than twice that measured after the first dose. Pyrimethamine concentration in CSF was 25 to 50% of corresponding plasma concentration and did not appear to accumulate with successive administration of doses. Blood samples collected during and after the dosing regimen were submitted for hematologic analysis; neutrophil numbers decreased slightly, but remained within normal range for adult horses.

Administration, Oral↗
PubMed1990

Endoscopic diagnosis of unilateral ectopic ureter in a yearling filly.

Unilateral ectopic ureter was diagnosed by endoscopic examination in an 18-month-old filly examined because of chronic urine dribbling. Intramuscular administration of azosulfamide discolored the urine and enhanced visualization of the ectopic ureter. Endoscopy proved valuable in determining that only one ureter entered the urinary bladder and in locating the ectopic ureter in the ventral portion of the vagina.

Animals↗
PubMed1990

Lymphocytic-plasmacytic enteritis in two horses.

The primary hematologic abnormalities in 2 adult horses with chronic weight loss were hypoalbuminemia and hyperglobulinemia. One horse was anemic, had subclinical disseminated intravascular coagulation, and prolonged plasma sulfobromophthalein half-life. Small-intestinal dysfunction with malabsorption was indicated by abnormal D-xylose absorption test results. Clinicopathologic and pathologic findings were consistent with a diagnosis of malabsorption and protein-losing enteropathy, attributable to lymphocytic and plasmacytic infiltration of the intestine.

Animals↗
PubMed1989

Interactions between chloramphenicol, acepromazine, phenylbutazone, rifampin and thiamylal in the horse.

The potential for interactions between chloramphenicol, phenylbutazone, acepromazine and thiamylal and chloramphenicol, rifampin, and phenylbutazone were evaluated in two groups of experiments. In the first, five horses were given thiamylal intravenously (iv) (6.6 mg/kg) after pretreatment with acepromazine, and the time of recumbency was determined. Administration of chloramphenicol iv (25 mg/kg) 1 h prior to anaesthesia significantly lengthened the recumbency time from 21.8 +/- 4.8 mins to 36.0 +/- 8.3 mins. There was an apparent but not statistically significant decrease in recumbency time when phenylbutazone (4.4 mg/kg) was administered iv daily for 4 days prior to anaesthesia. In the second series of experiments, phenylbutazone (4.4 mg/kg), chloramphenicol (25 mg/kg) and rifampin (10 mg/kg) were administered in various sequences to five different horses. Chloramphenicol pretreatment produced a significant decrease in the elimination rate and rifampin a significant increase in the elimination rate of phenylbutazone. The half-life of elimination of phenylbutazone alone was about 4 h. Following four days pretreatment with rifampin it was approximately 2.7 h, it was approximately 5.6 h and 9.5 h, respectively, when chloramphenicol was administered in one dose 1 h before or two doses 12 h and 1 h before phenylbutazone.

Acepromazine↗
PubMed1987

Hematologic values in horses and interpretation of hematologic data.

Normal reference ranges and pertinent background information on equine hematology are presented and briefly discussed. Diagnostic interpretation of hematologic data is discussed and three diagnostic algorithms and two diagnostic tables are provided to facilitate the use of the presented information for diagnosis. Two cases are presented and the information presented in the article is used to interpret the case data.

Animals↗
PubMed1987

Collection and evaluation of equine peritoneal and pleural effusions.

This article discusses collection, slide preparation, culture technique, fluid analysis and evaluation, and cytologic evaluation of peritoneal and pleural effusions. The morphologic characteristics of various effusions are described, and the physical characteristics (volume, color, turbidity) of effusions are discussed. An algorithm for classifying effusions as transudates, modified transudates, or exudates is included, and each category is discussed.

Animals↗
PubMed1986

Clostridium perfringens type C enterotoxemia in a newborn foal.

A 1-day old, full-term foal with a history of colic died 2 hours after admission. Necropsy revealed an extremely flaccid, fluid-filled intestinal tract. Histopathologically, the superficial intestinal mucosa was completely necrotic, with minimal inflammatory response. Numerous large, gram-positive rods covered the villi. Clostridium perfringens was isolated on bacteriologic culturing of the intestinal tract contents and was identified as type C by toxin neutralization tests.

Animals↗
PubMed1985

Rifampin in the horse: comparison of intravenous, intramuscular, and oral administrations.

The plasma concentrations and pharmacokinetics of rifampin disposition were determined after a single IV, IM, or oral dose of 10 mg/kg of body weight and an oral dose of 25 mg/kg. The overall elimination rate constants per minute were similar for the 10 mg/kg dose (0.0021 +/- 0.0004, IV; 0.0017 +/- 0.0002, IM; and 0.0023 +/- 0.0006, orally). The apparent bioavailability was moderate to low for IM and oral administrations (59.8% +/- 3.2% and 39.5% +/- 5.0%, respectively). The rate of absorption was most rapid for oral administration with an absorption half-life of 249.7 +/- 71.6 minutes as compared with 403.5 +/- 89.7 minutes for IM administration. However, the IM route produced longer detectable plasma concentrations (50 hours in 2 of the 4 horses). Based on bacterial sensitivity information derived for human and canine isolates, the daily oral administration of 10 mg of rifampin/kg administered in the feed represents a reasonable dose for susceptible gram-positive bacterial pathogens. Higher doses (greater than or equal to 25 mg/kg) or IV administration would be required for most gram-negative bacteria. Adverse effects of sufficient severity to limit use of the drug, especially by the oral route of administration, were not encountered under the single-dose experimental conditions used.

Administration, Oral↗
PubMed1983

Effects of toxic doses of phenylbutazone in ponies.

Toxic doses of phenylbutazone (10 mg/kg of body weight) were administered to 10 ponies once daily for 14 days. Clinical signs of toxicosis similar to those seen in other species included CNS depression, anorexia, oral ulcers, and soft feces. Six ponies died in 7 to 20 days; 1 pony was euthanatized during an acute abdominal crisis; and 3 ponies survived the study. At necropsy, the major lesions were oral and gastrointestinal ulcerations and renal changes.

Administration, Oral↗
PubMedDate not supplied

Effect of a histamine H2 type receptor antagonist (WY 45, 727) on the healing of gastric ulcers in ponies.

Using video gastroscopy, the efficacy of a Histamine-H2 type receptor antagonist (WY 45, 727) was investigated in young ponies with spontaneous and experimentally induced gastric ulcers. Oral administration of WY 45, 727 at 2 mg/kg and 10 mg/kg of body weight every 12 hours for 14 days resulted in complete healing of spontaneous gastric ulcers in the non-glandular portion of the stomach in 2/5 (40%) and 3/4 (75%) of the ponies, respectively, compared (P < 0.05) to 0/5 (0%) placebo-treated ponies. After intramuscular administration of flunixin meglumine at 1.5 mg/kg body weight every 8 hours for 6 days, 9/18 ponies had ulcers in the non-glandular portion of the stomach. Oral administration of WY 45, 727 at 10 mg/kg body weight every 12 hours for 14 days resulted in complete healing of the non-glandular gastric ulcers in 3/4 (75%) compared with (P < 0.05) 1/5 (20%) placebo-treated ponies. This study indicates that 1) the occurrence of subclinical ulcers may be common in young ponies; 2) flunixin meglumine at 1.5 mg/kg intramuscularly every 8 hours for 6 days may result in ulcers of the non-glandular stomach in ponies; and 3) WY 45, 727, a histaminergic H2 type receptor antagonist could be of value in the therapeutic management of ulcers in the non-glandular stomach of foals and adult horses.

Administration, Oral↗