Determination of ceftiofur and its desfuroylceftiofur-related metabolites in swine tissues by high-performance liquid chromatography.

An HPLC method was developed and validated for the determination of ceftiofur-related metabolites that have the potential to be microbiologically active in swine muscle, kidney, liver and fat. Its performance was evaluated against incurred-residue swine tissues. This method is based on the cleavage of the disulfide and/or thioester bonds between the metabolites and their conjugate sulfur containing moiety using dithioerythritol to yield desfuroylceftiofur, and further stabilization to desfuroylceftiofur acetamide. The limit of quantitation was 0.1 micrograms ceftiofur equivalents/g tissue. The assay is specific for ceftiofur-related metabolites when evaluated against commercially available antibiotics for swine.

Modified microbiological method for the screening of antibiotics in milk.

The Bacillus stearothermophilus disc assay is routinely used by the dairy industry to screen milk for antibiotic residues. Although the assay detects the presence of beta-lactam antibiotics, it does not distinguish cephalosporins from other beta-lactam antibiotics. In this study, the B. stearothermophilus disc assay was modified to allow it to distinguish parent ceftiofur from other antibiotics by incorporation of the enzymes penicillinase and cephalosporinase into the assay. The modified B. stearothermophilus disc assay involves determining the zone of inhibition of a sample on an agar plate after the plate was incubated at 65 degrees C for 2.5 to 3 h as well as determining the zone of inhibition after the sample was treated with penicillinase or cephalosporinase. Samples in which this zone diameter was > 19 mm and < or = 25 mm were interpreted using the data from the primary assay. Samples with zone diameters > 25 mm must be diluted 2- to 10-fold and reassayed to obtain a zone diameter > 19 and < or = 25 mm, for proper interpretation. Samples with zone diameters > or = 16 mm and < or = 19 mm must also be reassayed using dilute enzyme solutions for proper interpretation. When these modifications of the B. stearothermophilus disc assay are used, ceftiofur can be distinguished from ampicillin, amoxicillin, penicillin, cephapirin, cloxacillin, novobiocin, and pirlimycin for samples with zone diameters > or = 16 mm. This assay cannot, however, separate ceftiofur from cefazolin.(ABSTRACT TRUNCATED AT 250 WORDS)

Concentration of ceftiofur metabolites in the plasma and lungs of horses following intramuscular treatment.

Ceftiofur sodium, a broad spectrum cephalosporin antibiotic approved for veterinary use, is metabolized to desfuroylceftiofur which is conjugated to micro as well as macromolecules. Twelve horses, weighting 442-618 kg, were injected intramuscularly with a single dose of 2.2 mg ceftiofur/kg (1.0 mg/lb) body weight. Blood was collected at various intervals over 24 h after treatment. Three groups of four horses each were euthanized and lungs were collected at 1, 12, and 24 h after treatment. The concentration of desfuroylceftiofur and desfuroylceftiofur conjugates in the plasma and lungs was determined by converting them to desfuroylceftiofur acetamide (DCA) and measured DCA by high performance liquid chromatography with UV detection. The average maximum concentration (Cmax) of desfuroylceftiofur and related metabolites in plasma expressed as ceftiofur equivalents was 4.46 +/- 0.93 micrograms/ml occurred at 1.25 +/- 0.46 h after treatment. These concentrations declined to 0.99 +/- 0.16, 0.47 +/- 0.15 and 0.17 +/- 0.02 microgram/ml at 8, 12, and 24 h, respectively. The mean residence time of ceftiofur metabolites was 6.10 +/- 1.27 h. Concentrations of desfuroylceftiofur and desfuroylceftiofur conjugates in the lungs of horses expressed as ceftiofur equivalents were 1.40 +/- 0.36, 0.27 +/- 0.07, and 0.15 +/- 0.08 micrograms/ml at 1, 12, and 24 h, respectively. These concentrations of the drug at 12 and 24 h in lung homogenate were similar but slightly lower than plasma concentrations in the same horses, and the plasma pharmacokinetic values including half-life were similar to those observed at the approved dose of 1.1-2.2 mg ceftiofur/kg body weight administered intramuscularly once daily for 3-5 days in cattle.

Depletion of intramuscularly injected ceftiofur from the milk of dairy cattle.

Ceftiofur sodium, a new broad-spectrum cephalosporin, has been approved in the US, Canada, and several other countries throughout the world to treat bovine respiratory disease in cattle and dairy cows. In Experiment 1, 6 lactating cows were intramuscularly treated with 2.29 mg of [14C]ceftiofur/kg of BW daily for 5 d. In Experiment 2, 30 additional cows at three locations were similarly treated with 2.2 mg of ceftiofur (unlabeled)/kg of BW. Milk was collected every 12 and 24 h after each dose and every 12 h up to 5 d after the last dose. The majority of milk samples, both during treatment (12 and 24 h after each dose) and after the last dose (up to 5 d following ceftiofur treatment), were negative by screening procedures based on microbial inhibition (Delvotest-P, Bacillus stearothermophilus disk assay, and cylinder plate assays). The receptor-binding Charm Test II assay, which has a limit of detection of .005 ppm of ceftiofur, gave positive tests for milk samples up to 48 h following treatment. When the Charm Test II assay is used with .008 IU/ml of penicillin as a positive control, 44% of the samples from individual cows were negative at 12 h posttreatment. Ninety percent of the samples from individual cows were negative at 24 h after the last treatment. The use of ceftiofur in dairy cattle in accordance with the label directions does not result in total residues in milk higher than the FDA-calculated safe concentration of 1-ppm ceftiofur equivalents. The milk from individual cows did not test positive by the commercial screening assays examined in this study, except for the Charm Test II. The Charm Test II was 90% negative using the Charm Sciences criteria at 24 h after the last treatment.

Liquid chromatographic determination of desfuroylceftiofur metabolite of ceftiofur as residue in cattle plasma.

A liquid chromatographic (LC) method has been developed for the determination of the desfuroylceftiofur metabolite of ceftiofur as a residue in the plasma of animals. Plasma sample in 0.1M pH 8.7 phosphate buffer containing dithioerythritol is incubated under nitrogen for 15 min at 50 degrees C. The sample is centrifuged, charged to a C18 cartridge, and washed with 0.1M ammonium acetate. The desfuroylceftiofur residue on the cartridge is derivatized by adding 0.1M ammonium acetate containing iodoacetamide and letting the cartridge stand in the dark for 30 min. The cartridge is then drained and rinsed, and the desfuroylceftiofur acetamide is eluted with methanol. The mixture is evaporated to dryness, dissolved in pH 10.6 sodium hydroxide, and charged to a SAX cartridge. The derivative is eluted with 2% acetic acid, reduced in volume, and dissolved in mobile phase for liquid chromatography. The LC system includes a C8 column and guard cartridge with UV detection at 254 nm. The gradient mobile phase (flow rate 1 mL/min) is 0.01M pH 5 ammonium acetate programmed to 29% methanol-water (60 + 40) in 25 min. Recoveries were 90-100% with a sensitivity of 0.1 ppm or less. The procedure has been applied to the plasma of cattle, rats, horses, pigs, and dogs.

Changes in thymidine uptake in the gastrointestinal tract of the rat following treatment with 16,16-dimethyl prostaglandin E2.

Thymidine uptake in the organs of the gastrointestinal tract of the rat was studied to determine if cell synthesis was involved in the increases in weight of the stomach, small intestine and colon which result from treatment with 16,16-dimethyl prostaglandin E2 (16,16-dimethyl PGE2). Animals were treated for 2 days with 16,16-dimethyl PGE2. They were injected with the 3H-thymidine, sacrificed and the organs of interest were removed. The total amount of tritium in the stomach, duodenum, jejunum, ileum, and colon was determined. Thymidine uptake was significantly increased in the duodenum (1.50 times), jejunum (1.53 times), and colon (1.40 times) but not in the stomach and ileum. The increases were dose related in the duodenum and jejunum. The colon showed a similar dose response pattern but the changes with dose did not reach significance. These results confirm and extend a previous report that 16,16-dimethyl PGE2 increased thymidine uptake in the duodenum but not the stomach. This is different from gastrin which has been shown by others to increase thymidine uptake in the stomach, duodenum, ileum and colon.

Quantitative determination of N-(trans-2-dimethylaminocyclopentyl)-N-(3',4'-dichlorophenyl) propanamide and its N-demethyl metabolite in dog serum by gas chromatography.

A gas chromatographic-electron capture (GC-EC) method has been developed for the determination of N-(trans-2-dimethylaminocyclopentyl)-N-(3',4'-dichlorophenyl)pr opanamide, a potential antidepressant drug, and its N-demethyl metabolite in serum. The GC-EC system employed a 3% OV-17 on 100/120 mesh Supelcoport, 2-m X 2-mm i.d. glass column and an isothermal temperature of 195 degrees C. The parent drug and metabolite were extracted from alkalinized serum (pH approximately 13) with toluene, back-extracted into an acidic solution (pH approximately 1), and finally, after adjusting to pH 13, extracted again with toluene. The extensive sample cleanup was necessary to remove serum components which interfered with the analysis. The analytical method was shown to give quantitative recovery of the drug and metabolite, to be linear over a 100-fold concentration range, and to have the necessary precision and sensitivity to detect and quantify as little as 1 ng/mL of the drug or its metabolite. The method has been employed to determine the serum level of drug and metabolite in dogs receiving a single oral dose and to determine the possible correlation between the administered dose and serum levels.

Aspirin-induced damage in the dog Heidenhain pouch and cytoprotection with 16,16-dimethyl PGE2.

The gastric mucosa of animals and man can be damaged by noxious agents and protected by prostaglandins. We developed a Heidenhain pouch dog model which allows the study of multiple doses of the protective or noxious agent. Mucosal damage in the pouch caused by instillation of 160 mM aspirin suspended in 150 mM HCl for two 15-min periods was determined by measuring hemoglobin concentration in isotonic mannitol washes. Hemoglobin levels 24 h after the administration of the acid-aspirin suspension were significantly higher than basal levels. Pretreatment with oral doses of 0.3-3 micrograms/kg 16,16-dimethyl PGE2 at 24 and 18 h and 30 min before the acid-aspirin suspension decreased hemoglobin concentrations in the washes (p less than 0.001).

Partial characterization of the gastrointestinal weight changes produced in the female rat by 16,16-dimethylprostaglandin E2.

Oral and subcutaneous administration of 16,16-dimethylprostaglandin E2 (16,16-dimethyl PGE2) resulted in an increase in the dry weight of the stomach and small intestine of the female rat. This weight response was rapid, controlled rather than continuously progressing, dose dependent and reversible. The dry weight of the colon also increased but this was not studied in detail. Two-day treatment with 16,16-dimethyl PGE2 caused an increase in the incorporation of 3H-thymidine into the duodenum, jejunum and colon suggesting an increase in cell number. Incorporation into the stomach and ileum was not changed. The number of goblet cells per crypt was increased by prostaglandin treatment in all parts of the small intestine. Since these are mucus producing cells, the small intestine may have increased in cell number and mucus production. Both anti-secretory and cytoprotective doses of 16,16-dimethyl PGE2 caused weight increases in the stomach and small intestine. However, the weight gain by itself was not sufficient to protect the stomach or small intestine from necrotic agents after the prostaglandin was discontinued.

Serum total hydroxyproline assay: effects of age, sex and Paget's bone disease.

An assay was developed for total hydroxyproline (protein, peptide and free) in 12 h fasted human serum. Values obtained from 80 adults judged normal by laboratory and physical examinations showed age and sex effects; values increased with age and were higher for men. Assay of serum samples from 22 patients with Paget's bone disease revealed values significantly above normal taking age and sex into consideration (p = 0.001). Serum alkaline phosphatase and serum hydroxyproline values for these patients were correlated (r = 0.91). Serum total hydroxyproline may be a useful assay for evaluating metabolic bone diseases but age and sex must be taken into consideration in the interpretation.

Influence of kaolin-pectin suspension on steady-state plasma digoxin levels.

The effect of a kaolin-pectin antidiarrheal mixture on steady-state plasma levels of orally administered digoxin in subjects receiving chronic digoxin therapy was evaluated when the antidiarrheal and the cardiac glycoside were given concomitantly and when two doses of antidiarrheal were given, one 2 hours before and the other 2 hours after digoxin. Although simultaneous administration of both products decreased peak digoxin levels by 36 per cent, 24-hour areas under the curve were reduced by only 15 per cent, indicative of a slight decrease in digoxin bioavailability. In contrast, when their times of administration were separated by 2 hours, no evidence of a drug interaction was noted. Hence, the effect of one or two doses of kaolin-pectin suspension on steady-state plasma levels of digoxin appears inconsequential in patients on chronic digoxin therapy. Saliva levels were poorly correlated with plasma levels, presumably because of complexation in the oral cavity.

A seasonal variation study of 25-hydroxyvitamin D3 serum levels in normal humans.

A population residing in the approximate area of Kalamazoo, MI (latitude north, 42 degrees 17' 29''; longitude west 85 degrees 35' 14''), was examined to determine the influence of seasonal variation on human 25-hydroxyvitamin D3 serum levels. Males and females, ranging in age from 16--64 yr of age and judged normal based on laboratory evaluation and physical examination, participated in the 12-month study. Measurement of 25-hydroxyvitamin D3 serum levels was made by high performance liquid chromatography. A correlation coefficient of 0.776 (P = 0.003) was obtained by comparing average monthly 25-hydroxyvitamin D3 serum levels to average monthly temperatures. A comparison of approximated monthly amounts of sunlight to average monthly 25-hydroxyvitamin D3 serum levels produced a correlation coefficient of 0.747 (p = 0.005). In addition, changes in 25-hydroxyvitamin D3 levels for the population examined fitted a model that demonstrated a relationship to sex and a highly significant periodic relationship to time.

Mammary tumors and serum hormones in the bitch treated with medroxyprogesterone acetate or progesterone for four years.

After 4 years of a long-term contraceptive steroid safety study, the incidence and the histologic types of mammary dysplasia produced are shown to be similar in beagles treated with medroxyprogesterone acetate (medroxyprogesterone) or progesterone. Serum insulin, thyroid-stimulating hormone (TSH), triiodothyronine, growth hormone, prolactin, 17 beta-estradiol, progesterone, and cortisol were determined by radioimmunoassay on samples collected after 45 months of treatment. Serum growth hormone and insulin concentrations were elevated in a dose-related manner in both treatment groups. Levels of triiodothyronine, cortisol, and 17 beta-estradiol (medroxyprogesterone only) were lowered. TSH and prolactin concentrations were not changed. Pituitary-gonadal hormone interaction in the pathogenesis of mammary neoplasia of the dog is discussed. Prolonged treatment of beagles with doses of progesterone or medroxyprogesterone 1 to 25 times the human contraceptive dose or luteal phase (dog) levels, respectively, results in a dose-related incidence of mammary nodules.

PIP: The results of a 4-year longterm study of contraceptive safety in mammals are discussed. The animals were treated with either MPA (medroxyprogesterone acetate) or progesterone. Serum insulin, thyroid-stimulating hormone, triiodothyronine, growth hormone, prolactin, 17 beta-estradiol, progesterone, and cortisol were measured by radioimmunoassay on samples collected after 45 months of treatment. No increased incidence of mammary tumors were noted in rats, mice, or monkeys. An increased incidence of mammary dysplasia was, however, noted in dogs. MPA and progesterone produced similar incidence rates, types, and numbers of nodules per animal. The incidence of mammary nodules was dose-related. Microscopic examination of the nodules indicated a similar histology and distribution of change in bitches treated with both substances. Serum prolactin, growth hormone, and insulin responses were similar in both groups. Clinical studies with women being treated with either MPA or progesterone have shown no evidence of treatment-related mammary dysplasia. These studies revealed several significant differences in hormonal response to exogenous progestational compounds between dogs and humans.

Some problems in development of a high-performance liquid chromatographic assay to measure 25-hydroxyvitamin D2 and 25-hydroxyvitamin D3 simultaneously in human serum.

A high-performance liquid chromatographic technique was examined that may allow simultaneous measurement of 25-hydroxyvitamin D2 and 25-hydroxyvitamin D3 in a single sample of human serum. Concentrations of 4 microgram/liter or greater are accurately measured. However, the prepurification procedure allows partial separation of the two metabolites, and so tritiated 25-hydroxyvitamin D3 can be used as an internal standard for accurately monitoring the analytical recovery of 25-hydroxyvitamin D3, but not that of 25-hydroxyvitamin D2. The ability of most prepurification procedures to partly separate the 25-hydroxy metabolites of vitamin D2 and D3 mandates the need for individual internal standards to accurately monitor the recovery of each compound. Values obtained for 25-hydroxyvitamin D2 or composite 25-hydroxyvitamin D when only tritiated 25-hydroxyvitamin D3 is used as a means of monitoring recovery are probably in error.

The effect of prostaglandin E2-induced echinocytic transformation on the potassium loss, viscosity and osmotic fragility of normal and sickle cell erythrocytes.

Prostaglandin E2 (PGE2)-induced discocyte leads to echinocytic transformation has no effect on the viscosity or osmotic fragility of normal or sickle cell erythrocytes. Membrane permeability, reflected as potassium efflux, is significantly affected in normal erythrocytes when greater than 90% of the cells are morphologically transformed to the echinocytic III stage (PGE2 concentration of 1--2x10(6) ng/ml blood). This potassium loss is significant in sickle erythrocytes when 50-70% of the cell population has been transformed (PGE2 concentration, 5x10(5) ng/ml blood). This change in membrane permeability represents one-half to one-third the flux that occurs with sickling (i.e., greater than 80% of the erythrocytes sickled).

High-performance liquid chromatographic assay for 25-hydroxyvitamin D3 in serum.

We describe a precise and specific method for measuring 25-hydroxyvitamin D3 in 1 ml of human serum. Extraction with chloroform/methanol followed by chromatography on a 0.5 X 2-cm silica gel column yields a sample that is sufficiently free of extraneous material for high-performance liquid chromatography on a column of microporous silica gel (10 micron average particle diameter). The measurement is not influenced by vitamins D2 or D3, 25-hydroxyvitamin D2, or any of the more hydroxylated metabolites of the vitamin D group. Results by this method correlate well with a competitive protein-binding assay (r = 0.961), but with a negative bias of 6.9 +/- 3.3 microgram/liter. We measured concentrations of 25-hydroxyvitamin D3 in serum drawn during February from 24 persons who were judged normal by physical examinations. The range was 5.5-23.8 microgram/liter (mean, 15.0 +/- 5.2 microgram/liter). The day-to-day CV for the assay was 5.46%.

Radioimmunoassay of minoxidil in human serum.

A simple, sensitive, and specific radioimmunoassay for determining minoxidil was developed. Antiserums to two minoxidil haptens were compared for cross-reactivity and assay levels on human serums. One antiserum had little cross-reactivity with minoxidil metabolites. The radioimmunoassay is specific for determining minoxidil directly in serum without extraction. Human serum minoxidil levels were determined from a single oral dose.

Prostaglandin E2-hemoglobin AA and SS erythrocyte interaction (prostaglandin-erythrocyte interaction).

Prostaglandin E2 (PGE2), at concentration larger than or equal to 5 x 10(4) ng/ml, induced discocyte leads to echinocyte transformation of saline-suspended hemoglobin (Hb) AA and SS erythrocytes. This erythrocyte transformation is concentration-dependent and is reversible at room temperature after 90-120 min. The Hb SS erythrocytes treated with PGE2 did not exhibit accelerated sickling or increased formation of sickled echinocytes. Erythrocytes suspended in autologous plasma treated with PGE2, 2 X 10(6) ng/ml, did not exhibit echinocytic transformation probably because of drug binding to the plasma proteins. Other in vitro studies showed that PGE2 of concentrations of 10-500 ng/ml had no adverse effects on intact, plasma-suspended Hb SS erythrocytes. These Hb SS erythrocytes were examined for changes in morphology, potassium and calcium flux, and blood viscosity under oxygenated and hypoxic conditions.

Anorectal pruritus after intravenous hydrocortisone sodium succinate and sodium phosphate.

A double-blind study demonstrated that single intravenous doses of 100, 200, or 400 mg of hydrocortisone sodium succinate and hydrocortisone sodium phosphate were similar in eosinophil suppression, elevation of glucose, white blood count differential shifts (polymorphonuclear cells, lymphocytes, and monocytes), and urinary excretion of sodium and potassium but not in incidence of side effects. More subjects receiving hydrocortisone sodium phosphate experienced systemic or localized adverse effects than those receiving hydrocortisone sodium succinate. The most common side effect was burning or itching in the anorectal area, which occurred in 16 of 18 subjects medicated with hydrocortisone sodium phosphate, in 1 subject of 6 treated with placebo (saline), and in none who received the sodium succinate. The effect is attributed to the phosphate steroid and appears to last as long as it takes to convert to cortisol.