Furazolidone concentrations in plasma, milk and some tissues of Nubian goats

The concentrations of furazolidone (FZ) in plasma and milk were measured in goats treated orally with the drug at a dose of 10 mg kg-1 daily for 5 days. The maximum plasma concentrations obtained were 1.57 +/- 0.52 micrograms ml-1 (n = 5) 8 h after the first dose, and 2.13 +/- 0.11 micrograms ml-1 (n = 4) 6 h after the fifth dose. The maximum milk concentration was 0.88 +/- 0.32 micrograms ml-1 (n = 4) 8 h following the administration of a single dose. Using a colorimetric method, FZ was not detectable in goats' liver or muscle after the recommended therapeutic dose (10 mg kg-1, 5 days). However, using an HPLC method, the drug was detected 24 h after the treatment in the gluteal muscle and liver at concentrations of 0.26 +/- 0.01 microgram g-1 (n = 5) and 0.10 +/- 0.02 microgram g-1 (n = 5), respectively. The drug concentrations decreased significantly (P less than 0.05-0.01) at 3, 5 and 7 days after treatment, and no measurable concentrations were found after 10 days.     

Pharmacokinetics and renal clearance of ampicillin in sheep

Pharmacokinetics and renal clearance of ampicillin were investigated in 13 sheep, following one single oral dose of 750 mg. A peak concentration in plasma 0.38 +/- 0.04 microgram/ml (mean +/- SEM) was achieved 95.3 +/- 5.95 min after drug administration. Absorption half-life was 44.4 +/- 4.4 min. The area under the plasma concentration curve was 94.6 +/- 4.5 micrograms.hour.ml-1, while in the case of urine it was 370.5 +/- 28.3 micrograms.hour.ml-1. Biological half-life of ampicillin was 110 +/- 3 min, with an elimination rate constant of 0.0064 +/- 0.0002 min-1. The values for volume of distribution and total body clearance were 8.2 +/- 0.71/kg or 52.0 +/- 4.2 ml/kg/min, respectively. The priming and maintenance doses, using MIC as 0.05 microgram/ml, were suggested to be 8.8 or 8.4 mg/kg, respectively, at an 8-h interval. For MIC of 0.5 microgram/ml, this dose should be 10 times higher. Renal clearance of ampicillin seemed to involve active tubular secretion. Renal excretion indicated either extensive metabolism or excretion through routes other than kidneys.     

Disposition kinetics and dosage regimen of ceftriaxone in crossbred calves (short communication).

Disposition kinetics and urinary excretion of ceftriaxone were investigated in healthy crossbred calves after its single intravenous administration (10 mg kg-1). Based on kinetic parameters, an appropriate dosage regimen of ceftriaxone in calves was calculated. The peak plasma level of ceftriaxone at 1 min was 84.0 +/- 1.55 micrograms ml-1 which declined to 0.43 +/- 0.05 microgram ml-1 at 8 h. The value of elimination half-life (t1/2 beta), volume of distribution Vd (area) and total body clearance (ClB) were 4.39 +/- 0.63 h, 1.91 +/- 0.19 L kg-1 and 0.31 +/- 0.01 L kg-1 h-1, respectively. Approximately 41 per cent of total administered drug was recovered in the urine within 24 h of its administration. The plasma protein binding of ceftriaxone was found to be concentration dependent with an overall mean of 38.55 per cent. The binding capacity of ceftriaxone to plasma proteins and the dissociation rate constant of protein-drug complex were 20.1 x 10(-8) +/- 18.4 x 10(-8) mole g-1 and 1.07 x 10(-6) +/- 0.52 x 10(-6) mole, respectively. An appropriate intravenous dosage regimen of ceftriaxone in cattle would be 12 mg kg-1 repeated at 24 h.     

Pharmacokinetics of norfloxacin and its N-desethyl- and oxo-metabolites in broiler chickens.

Norfloxacin was given to 2 groups of chickens (8 chickens/group) at a dosage of 8 mg/kg of body weight, IV and orally. For 24 hours, plasma concentration was monitored serially after each administration. Another group of chickens (n = 30) was given 8 mg of norfloxacin/kg orally every 24 hours for 4 days, and plasma and tissue concentrations of norfloxacin and its major metabolites desethylenenorfloxacin and oxonorfloxacin were determined serially after the last administration of the drug. Plasma and tissue concentrations of norfloxacin, desethylenenorfloxacin, and oxonorfloxacin were measured by use of high-performance liquid chromatography. Pharmacokinetic variables were calculated, using a 2-compartment open model. For norfloxacin, the elimination half-life (t1/2 beta) and the mean +/- SEM residence time for plasma were 12.8 +/- 0.59 and 15.05 +/- 0.81 hours, respectively, after oral administration and 8.0 +/- 0.3 and 8.71 +/- 0.23 hours, respectively, after IV administration. After single oral administration, norfloxacin was absorbed rapidly, with Tmax of 0.22 +/- 0.02 hour. Maximal plasma concentration was 2.89 +/- 0.20 microgram/ml. Oral bioavailability of norfloxacin was found to be 57.0 +/- 2.4%. In chickens, norfloxacin was mainly converted to desethylenenorfloxacin and oxonorfloxacin. Norfloxacin parent drug and its 2 major metabolites were widely distributed in tissues. Considerable tissue concentrations of norfloxacin, desethylenenorfloxacin, and oxonorfloxacin were found when norfloxacin was administered orally (8 mg/kg on 4 successive days). The concentration of the parent fluoroquinolone in fat, kidneys, and liver was 0.05 micrograms/g on day 12 after the end of dosing.     

Preliminary pharmacokinetic study of isometamidium chloride in camels

Isometamidium chloride was given to camels at a single intravenous dose rate of 0.5 or 1 mg kg-1 and the plasma drug concentration measured spectrophotometrically at frequent intervals for up to 48 hours. Isometamidium chloride concentrations were found to be 9.8 +/- 0.2 and 8.7 +/- 0.2 micrograms ml-1 half an hour after treatment with 1 and 0.5 mg kg-1, respectively, and 1.7 +/- 0.3 and 0.7 +/- 0.3 micrograms ml-1 after 24 hours. No measurable drug concentration was found 48 hours after dosing.     

Pharmacokinetics of single doses of cefoperazone given by the intravenous and intramuscular routes to unweaned calves

Cefoperazone pharmacokinetics were studied in unweaned calves. The antibiotic was administered to 10 calves intravenously, to eight calves intramuscularly at 20 mg kg-1 and to 10 calves intramuscularly at 20 mg kg-1 together with probenecid at 40 mg kg-1. Serum concentration versus time data were analysed by non-compartmental methods based on the statistical moment theory. The intravenous data were also fitted by a linear, open two-compartment model. The terminal halflife of cefoperazone was 127.9 +/- 28.2 min (mean +/- SD) after intravenous and 136.9 +/- 19.6 min after intramuscular administration. The t1/2 was increased to 257.3 +/- 127.3 min by the co-administration of probenecid. The total body clearance was 8.16 +/- 1.60 ml min-1 kg-1 and the volume of distribution at steady state was 0.713 +/- 0.167 litre kg-1. The mean residence time values were 87.2 +/- 10.6 min after intravenous and 140.3 +/- 20.6 min after intramuscular injection and were increased to 264.5 +/- 99.8 min by the co-administration of probenecid. The estimated mean absorption time was 53.1 min and the estimated bioavailability after intramuscular administration was 76.3 per cent. The minimal inhibitory concentration (MIC90) values of cefoperazone ranged from 0.5 to 2 micrograms ml-1 for Escherichia coli, salmonella groups C, D and E and Pasteurella multocida isolates. Salmonella group B strains appeared to be highly resistant to cefoperazone with MIC90 greater than 32 micrograms ml-1. There were no significant differences between the pharmacokinetic variables calculated by statistical moment theory or compartmental analysis indicating central compartment output of cefoperazone.(ABSTRACT TRUNCATED AT 250 WORDS)     

Oxytetracycline pharmacokinetics, tissue depletion, and toxicity after administration of a long-acting preparation at double the label dosage

Oxytetracycline (OTC) concentration in plasma and tissues, plasma pharmacokinetics, depletion from tissue, and toxicity were studied in 30 healthy calves after IM administration of a long-acting OTC preparation (40 mg/kg of body weight) at double the label dosage (20 mg/kg). Plasma OTC concentration increased rapidly after drug administration, and by 2 hours, mean (+/- SD) values were 7.4 +/- 2.6 micrograms/ml, Peak plasma OTC concentration was 9.6 +/- 2.6 micrograms/ml, and the time to peak plasma concentration was 7.6 +/- 4.0 hours. Plasma OTC concentration decreased slowly for 168 hours (elimination phase) after drug administration, and the elimination half-life was 23.9 hours. Plasma OTC concentration exceeded 3.8 micrograms/ml at 48 hours after drug administration. From 168 to 240 hours after drug administration, plasma OTC concentration decreased at a slower rate than that seen during the elimination phase. This slower phase was termed the depletion phase, and the depletion half-life was 280.7 hours. Tissue OTC concentration was highest in kidneys and liver. Lung OTC concentration exceeded 4.4 micrograms/g of tissue and 2.0 micrograms/g of tissue at 12 and 48 hours after drug administration, respectively. The drug persisted the longest in kidneys and liver. At 42 days after drug administration, 0.1 micrograms of OTC/g of kidney was detected. At 49 days after drug administration, all OTC tissue concentrations were below the detectable limit. Reactions and toxicosis after drug administration were limited to an anaphylaxis-like reaction (n = 1) and injection site swellings (n = 2).     

Serum concentrations of cefepime (BMY-28142), a broad-spectrum cephalosporin, in dogs.

Serum concentrations of cefepime (BMY-28142) were determined for four dosing regimes, 10 mg/kg or 20 mg/kg, given as single subcutaneous (SC) or intramuscular injections (IM) to dogs. Serial serum samples were analyzed for the presence of cefepime by high-performance liquid chromatography. In experiment 1, the overall mean (+/- SEM) serum concentration (for a 12-hour period) after a dose of 20 mg/kg for SC and IM routes (4.9 +/- 0.74 micrograms/ml and 5.5 +/- 0.63 micrograms/ml, respectively) was twice that for the 10 mg/kg dose given either SC or IM (2.2 +/- 0.31 micrograms/ml and 2.8 +/- 0.47 micrograms/ml, respectively). There was no significant difference (p greater than 0.05) in mean serum concentrations for SC and IM routes of administration at the same dosage. In subsequent experiments, 5 doses of cefepime (20 mg/kg) were administered IM at 12-hour (experiment 2) or 24-hour (experiment 3) intervals. The mean (+/- SEM) peak serum concentration was 12.1 +/- 1.59 micrograms/ml, 2 hours after the 2nd injection in experiment 2. In experiment 3, the mean (+/- SEM) peak serum concentration was 10.9 +/- 1.34 micrograms/ml, 4 hours after the 1st injection. Mean trough concentrations in experiment 2 were greater than or equal to 0.5 microgram/ml and less than or equal to 0.5 in experiment 3. Multiple IM doses produced transient edema at the injection site and mild lameness in all dogs. Cefepime was highly active against single canine isolates of Staphylococcus intermedius, Pseudomonas aeruginosa and Escherichia coli, with minimum inhibitory concentrations of 0.125 microgram/ml, 1 microgram/ml and 0.3 microgram/ml, respectively.     

Effect of propranolol on growth hormone response to GH releasing hormone (GHRH 1-44) in the dog.

The present study was undertaken to examine whether beta-adrenergic blockade with propranolol might influence and make less variable the growth hormone (GH) response to exogenous GH releasing hormone (GHRH) 1-44 in the dog. On four separate occasions eight healthy beagles, one to two years old, randomly received either propranolol (40 micrograms kg-1 intravenously) or an equivalent volume of saline, 30 minutes before either GHRH 1-44 (1 microgram kg-1 intravenously) or vehicle was injected. After propranolol alone, GH secretion did not differ from saline (area under the curve [AUC]: 649.5 +/- 128.3 v 633.2 +/- 87.7 ng min ml-1, respectively). GHRH alone elicited a significant increase in GH secretion (AUC: 1230.5 +/- 210.5 ng min ml-1) with a peak concentration of 16.7 +/- 4.8 ng ml-1. When GHRH was injected after propranolol the mean peak (59.1 +/- 14.7 ng ml-1) and secretory area (AUC: 2631.0 +/- 474.4 ng min ml-1) were greater than those observed after GHRH alone. However, from a clinical point of view propranolol pretreatment does not modify the great individual variability of the GH response to GHRH.     

Comparison of pharmacokinetic variables for two injectable formulations of netobimin administered to calves

In a 4 x 4 crossover-design study, pharmacokinetic variables of 2 injectable formulations of netobimin (trisamine salt solution and zwitterion suspension) were compared after SC administration in calves at dosage of 12.5 mg/kg of body weight. Netobimin parent drug was rapidly absorbed, being detected between 0.25 and 12 hours after treatment, with maximal plasma drug concentration (Cmax) values of 2.20 +/- 1.03 micrograms/ml achieved at 0.75 +/- 0.19 hour (trisamine) and 1.37 +/- 0.59 micrograms/ml at 0.81 +/- 0.18 hour (zwitterion). Netobimin area under the plasma concentration-time curve (AUC) was 7.59 +/- 3.11 micrograms.h/ml (trisamine) and 6.98 +/- 1.60 micrograms.h/ml (zwitterion). Elimination half-life (t1/2 beta) was 2.59 +/- 0.63 hours (trisamine) and 3.57 +/- 1.45 hours (zwitterion). Albendazole was not detected at any time. Albendazole sulfoxide was detected from 4 hours up to 20 hours (trisamine) and from 6 hours up to 24 hours (zwitterion) after administration of the drug. The Cmax values were 0.48 +/- 0.16 micrograms/ml and 0.46 +/- 0.26 micrograms/ml for trisamine and zwitterion formulations, respectively, achieved at time to peak drug concentration (Tmax) values of 9.50 +/- 1.41 hours (trisamine) and 11.30 +/- 1.04 hours (zwitterion). Albendazole sulfoxide AUC was 3.86 +/- 1.04 micrograms.h/ml (trisamine) and 4.40 +/- 3.24 micrograms.h/ml (zwitterion); t1/2 beta was 3.05 +/- 0.75 hours (trisamine) and 3.90 +/- 1.44 hours (zwitterion). Albendazole sulfone was detected from 4 (trisamine) or 6 hours (zwitterion) to 24 hours after treatment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Penetration of tinidazole into the gingival crevicular fluid in dogs

Tinidazole was administered as a single oral dose of 15 mg kg-1 to 12 dogs, and its concentration in the plasma and gingival crevicular fluid (GCF) was measured at one and two hours by high performance liquid chromatography. Tinidazole was detectable in GCF in five dogs at one hour (6.8 +/- 2.6 micrograms ml-1) and in six dogs at two hours (9.2 +/- 1.4 micrograms ml-1) and in all plasma samples. In those animals with no detectable tinidazole in GCF, either the concentration of tinidazole in plasma was low or the volume of the GCF sample was insufficient for determination. The observed tinidazole levels in GCF exceeded the minimal inhibitory concentration values for most anaerobic oral bacteria.     

Trace element levels in liver and kidney from cattle, swine and poultry slaughtered in Canada.

Levels of arsenic, cadmium, copper, mercury and lead were determined in approximately 650 samples of liver and kidney from cattle, swine and poultry slaughtered in Canada during 1979-81. In addition zinc levels were determined in livers and kidneys from swine, and selenium and zinc levels were determined in the livers and kidneys from cattle. Depending on the element several methods of atomic absorption spectroscopy were used to analyze samples including flame, hydride generation, cold vapour generation and graphite furnace atomization. Analyses were also done by plasma emission spectroscopy. Levels of arsenic over 2.0 micrograms/g were detected in 0.9% of swine livers and 0.3% of swine kidneys. Cadmium levels higher than 1.0 micrograms/g were detected in 0.3% of cattle livers, 10.8% of cattle kidneys, 1.8% of swine kidneys, 0.4% of poultry livers and 0.3% of poultry kidneys. Levels of copper over 150 micrograms/g were detected in 0.4% of cattle and swine livers. Levels of lead over 2.0 micrograms/g were detected in 1.4% of poultry livers and 1.6% of poultry kidneys. The highest level of mercury detected in all species was 0.25 micrograms/g and the highest level of selenium was 1.9 micrograms/g. Zinc levels of over 100 micrograms/g were detected in 1.7% of cattle livers, 0.2% of cattle kidneys and 5.0% of swine livers.     

The distribution of vitamin A and retinol-binding protein in the blood plasma, urine, liver and kidneys of carnivores

The contents of retinol and retinyl esters as well as retinol-binding protein (RBP) in the plasma, urine, liver and kidneys of dogs, raccoon dogs and silver foxes were investigated. In the plasma and urine of all three species, vitamin A was present as retinol and retinyl esters. Vitamin A levels (1376+/-669 microg x g(-1)) were significantly higher in the livers of dogs than in the kidneys (200+/-217 microg x g(-1), P < 0.001 ). However, vitamin A levels in the kidneys of raccoon dogs (291+/-146 microg x g(-1)) and silver foxes (474+/-200 microg x g(-1)) were significantly higher than in the liver (67+/-58 microg x g(-1) and 4.3+/-2.4 microg x g(-1), respectively, both P < 0.001). RBP was immunologically detected in the blood plasma of all species, but never in the urine. In the liver, immunoreactive RBP was found in hepatocytes. In the kidneys of all species, RBP was observed in the cells of the proximal convoluted tubules. The levels of vitamin A in the livers of raccoon dogs and silver foxes were extremely low, which would be interpreted as a sign of great deficiency in humans. This observation might indicate that the liver status cannot be used as an indicator of vitamin A deficiency in canines. The high levels of vitamin A in the kidneys in all three species may indicate a specific function of the kidney in the vitamin A metabolism of canines.     

Alterations in the arrhythmogenic dose of epinephrine after adrenergic receptor blockade with prazosin, metoprolol, or yohimbine in halothane-xylazine-anesthetized dogs

Recent evidence has linked alpha-receptor and beta-receptor activations with ventricular arrhythmia genesis. In order to assess the relative contribution of specific adrenoceptors (alpha 1, alpha 2, beta 1) on ventricular arrhythmogenic activity during xylazine (1.1 mg X kg-1 X hr-1)-halothane (1.35%) anesthesia, the arrhythmogenic dose of epinephrine (ADE) was repeatedly determined before and after prazosin (alpha 1 antagonist; 0.1 mg X kg-1), metoprolol (beta 1 antagonist; 0.5 mg X kg-1), and yohimbine (alpha 2 antagonist; 0.125 mg X kg-1) administration in 6 dogs. The ADE was expressed as infusion rate and total dose. The ADE was defined as the dose which produced 4 or more intermittent premature ventricular contractions within 15 s during a 3-minute infusion period or within 1 minute from end of infusion. Control ADE was 2.69 +/- 0.372 (micrograms X kg-1 X min-1) and 4.17 +/- 0.544 (micrograms X kg X -1) for infusion rate and total dose, respectively. The ADE significantly increased after prazosin (P less than 0.005), metoprolol (P less than 0.005), and yohimbine (P less than 0.05) administration. The ADE values increased to 5.42 +/- 1.22 (rate) and 8.10 +/- 1.95 (dose) after alpha 2 blockade, but were significantly less than the alpha 1 and beta 1 blockade ADE values. In conclusion, although both alpha- and beta-adrenoceptor blockade depressed ventricular arrhythmia genesis in xylazine-halothane-anesthetized dogs, alpha 2 blockade, which was achieved with the recommended dose of yohimbine for reversal of anesthetic-induced CNS depression, was not as protective as alpha 1 (prazosin) or beta 1 (metoprolol) blockade.     

Method for the simultaneous determination of aflatoxins B1 and M1 in the liver of slaughter animals

The method used by Egmond et al. (1979) was chosen from a number of methods recommended for the determination of aflatoxins in raw materials of animal origin. This method is described in detail to facilitate its use in practice in cases of forced slaughters of animals suspected of aflatoxicosis. The sensitivity of the method for aflatoxin B1 and M1 is about 0.05 micrograms . kg-1. On the whole, 88 liver samples were examined for the presence of the aflatoxins B1 and M1. The samples had been obtained from the slaughtered pigs (52), bulls (23), cows (6), calves (5), and from deceased pigs (2). Positive findings were obtained in five of sixteen pork liver samples and in two of the tested five samples of calf liver. All of these animals were suspected of aflatoxicosis. At current slaughter, only one case of 36 examined pigs was found to be positive. Aflatoxin M1 was found more frequently than aflatoxin B1. However, the findings never exceeded the concentration of 100 ng . kg-1; this is less by 1.5 orders than the proposed tolerated concentration for adult animals (5 micrograms . kg-1).     

Concentrations of gentamicin in serum, milk, urine, endometrium, and skeletal muscle of cows after repeated intrauterine injections

Healthy mature cows (n = 6) were injected intrauterinally (IU) with gentamicin (50 ml of a 5% injectable solution) daily for 3 consecutive days. Venous blood and milk samples were collected at postinjection (initial) hours (PIH) 1, 3, 6, 9, 12, 24, 28, 31, 34, 37, 48, 51, 54, 57, 60, and 71, and endometrial biopsies were performed at PIH 6, 25, 48, 73, 95, and 119. Skeletal muscle biopsy samples were taken at PIH 25 and 73, and urine was collected every 1 or 2 hours during 12 consecutive hours after the first IU injection. Serum, milk, urine, and tissue concentrations of gentamicin were measured by radioimmunoassay. The highest mean serum concentration of gentamicin occurred during the 3 hours after each injection (2.49 +/- 1.46, 6.60 +/- 5.47, and 4.98 +/- 2.70 micrograms/ml). The mean peak concentration of gentamicin in milk occurred 3 to 6 hours after each injection. Mean peak urine concentration of gentamicin (256.8 +/- 127.9 micrograms/ml) was measured at PIH 6. The mean percentage of the first dose of gentamicin excreted in the urine within 12 hours was 14.78 +/- 3.56. The highest concentration of gentamicin in endometrial tissue (639.16 +/- 307.22 micrograms/g) was measured at PIH 6, decreasing to 9.64 +/- 3.55 micrograms/g before the next IU dose. Gentamicin was still detectable in endometrial tissue (0.86 +/- 0.43 microgram/g) 71 hours after the 3rd (last) IU injection.     

Pharmacokinetics and local tolerance of a long-acting oxytetracycline formulation in camels.

Disposition and local tolerance of a new oxytetracycline (OTC) long-acting formulation were evaluated in camels by measuring the dynamics of creatine kinase. Six camels (Camelus dromedarius) were administered OTC by IV and IM routes according to a 2-period cross-over, study design. Serum OTC concentration was measured, using a microbiological assay procedure. After IV administration (5 mg/kg of body weight), mean residence time was 7.7 +/- 2.8 hours, steady-state volume distribution was 706.1 +/- 168.6 ml.kg-1 and serum clearance was 75.3 +/- 23.2 ml.kg-1.h-1. After IM administration of the long-acting OTC formulation (10 mg/kg), maximal OTC concentration (3.49 +/- 0.44 micrograms.ml-1) was observed after 7.3 +/- 3.5 hours; the mean systemic availability was near 100%, and serum concentration greater than 0.5 micrograms.ml-1 was maintained for about 72 hours. After IM administration, mean control serum activity of creatine kinase was multiplied by a factor of 3.36 +/- 1.55; at 72 hours after OTC administration, the serum creatine kinase activity returned to control values. It was concluded that OTC is an antibiotic of potential interest in camels and that a dosage regimen of 10 mg.kg-1 deserves attention when using a long-acting formulation that has good local tolerance and near total systemic availability.     

Pharmacokinetics, bioavailability and dosage regimen of sulphadimidine in camels (Camelus dromedarius) under hot, arid environmental conditions

A two-way crossover study was conducted in young Bikaneri camels (aged between 12 and 18 months) during the hot summer season to determine the bioavailability, pharmacokinetics and dosage regimens of sulphadimidine (SDM). A dose of 100 mg.kg-1 of SDM was used to study both the intravenous and oral pharmacokinetics of the drug. Analysis of the intravenous data according to a two-compartment pharmacokinetic model revealed that SDM was well distributed in the body (Vd(area):0.862 L.kg-1), had an overall body clearance of 0.035 +/- 0.019 L.h-1.kg-1 and the elimination of half-lives was in the range of 14.2 to 20.6 h. The mean maximum plasma SDM concentration following oral administration was 63.23 +/- 2.33 micrograms.mL-1, which was achieved 24 h after the oral administration. The mean bioavailability of SDM following oral administration was approximately 100%. To achieve and maintain the therapeutically satisfactory plasma sulphadimidine levels of > or = 50 micrograms.mL-1, the optimum dosage regimen for camels following either intravenous or oral administration would be 110 mg.kg-1 as the priming dose and 69 mg.kg-1 as the maintenance dose, to be repeated at 24 h intervals.     

Thyroid function in relation to reproductive efficiency in postpartum buffaloes (Bubalus bubalis) during summer and winter

Thyroid function was studied by estimating of plasma-protein-bound iodine (PBI), in buffaloes, from 0 to 57 days postpartum. PBI values (microgram/100 ml) were lowest on day 1 postpartum, followed by a gradual increase by day 57. The values were consistently lower (P less than 0.01) during summer (3.79 +/- 0.13 micrograms/100 ml), as compared to winter (5.06 +/- 0.27). A lower value (P less than 0.01) was obtained in animals requiring less than 30 days (3.53 +/- 0.45) or more than 30 days (4.88 +/- 0.27) for uterine involution. The values were 4.56 +/- 0.13, 5.03 +/- 0.68 and 2.72 +/- 0.50 in animals requiring less than 25, 25-50 and more than 50 days for initiation of follicular development (P less than 0.01). Similarly the values were 4.95 +/- 0.38, 3.95 +/- 0.45 and 4.03 +/- 0.59 in buffaloes having postpartum oestrus intervals less than 45, 45-90, and more than 90 days (P less than 0.01). Higher values (P less than 0.05) were obtained in conceiving (4.55 +/- 0.41), as compared to non-conceiving animals (4.21 +/- 0.31). It can be concluded that the thyroid function is depressed during summer and in poorly reproducing buffaloes.     

Pharmacokinetic and pathological evaluation of gentamicin in cats given a small intravenous dose repeatedly for five days.

Gentamicin was administered to six cats at a dosage of 3 mg/kg of body weight intravenously every 8 h for five days. Peak and trough serum gentamicin concentrations were measured after each injection. Gentamicin elimination rate and serum half-life were calculated. Serum urea nitrogen, creatinine, biochemistry profile, electrolyte, glucose, total protein, and albumin concentrations were measured daily. Urinalyses were performed before and after the five-day experimental period. The mean +/- SD peak serum gentamicin concentration was 7.19 +/- 1.10 micrograms/mL, and the trough concentration was 0.59 +/- 0.09 microgram/mL. These concentrations are known to be effective against most gentamicin-sensitive bacteria. The mean +/- SD gentamicin elimination rate was 0.0065 +/- 0.0004 min-1. The harmonic mean +/- pseudo standard deviation serum half-life of gentamicin was 107.21 +/- 12.79 min. There were no significant increases (P greater than 0.05) in clinicopathological variables. Microscopic examination of renal sections did not disclose pathological lesions. Signs of vestibular impairment were not observed. A dosage of 3 mg gentamicin/kg given intravenously every 8 h for five days was determined to be safe and to produce therapeutic blood levels in cats.