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Biomedical subjects

G Ziv

Publications and source records attributed to G Ziv.

At least 73 records · Page 4Linked to original sources
PubMed1983

Encapsulated forms of slow-release dry cow products of rapidly absorbed antibiotics.

The persistence of chloramphenicol, cephacetrile, and clindamycin in the udders of dry cows was studied after drying-off therapy with salts of these antibiotics suspended in conventional oil bases. Antibiotic activity was not found in dry udder secretions collected 3-5 days after treatment. After equivalent doses of encapsulated formulations of chloramphenicol were suspended in the same oil bases and infused at drying-off, most of the drug remained bound within the microcapsules; chloramphenicol concentrations higher than 10 micrograms/ml secretion were maintained for 3-4 weeks, but upon release from the microcapsule, the free drug was very quickly absorbed from the udder. Microcapsulated formulations of cephacetrile and clindamycin were infused at drying-off, suspended in the same type of oil base and at similar doses to the non-capsulated preparations. The concentrations of free drug in the secretions remained constant over a period of 2-3 weeks, although total drug (bound and free) concentrations in the udder, which were much higher than free drug levels, were progressively and markedly reduced. It appeared that after infusion of the microcapsulated preparations of cephacetrile and clindamycin, rates of drug release from the depot were equal to the rates of absorption of free drug from the udder.

Animals↗
PubMed1983

Concentrations of methicillin in blood, normal milk and mastitic milk of cows after intramuscular injection of methicillin and tamethicillin.

Tamethicillin (TAM) is a basic ester pro-drug of methicillin (MET) which is converted in the body by non-specific esterases to MET. Equal doses of MET and TAM were administered intramuscularly in a crossover trial involving four dairy cows. Acute mastitis was induced in each cow by infusing two quarters of the udder with Escherichia coli endotoxin 3 h before antibiotic administration. Peak serum MET concentrations after MET injection were significantly (P less than 0.001) higher than peak serum drug concentrations after TAM injection. The t1/2 of MET in serum after MET and TAM treatments were 18 min and 2 h, respectively. Normal milk MET concentrations during the first 8 h after TAM administration were significantly (P less than 0.05) higher than after MET treatment. Mastitic milk MET concentrations during the period 2-6 after MET injection were significantly (P less than 0.01) higher than after TAM administration. However, MET concentrations which were equal to or higher than the minimal inhibitory concentrations for penicillin G-resistant staphylococci were maintained in the mastitic milk for 8 h after treatment with MET and TAM.

Animals↗
PubMed1983

Age-dependent pharmacokinetics of oxytetracycline in ruminants.

Oxytetracycline (OTC) was administered intravenously (i.v.) to 3- and 12-week-old calves and lactating cows, and both i.v. and intramuscularly (i.m.) to 14-week-old calves and non-lactating cows. Concentrations of OTC were determined in plasma and were analysed kinetically. The pharmacokinetic parameters which were derived using the three-compartment open model were inadequate to describe plasma drug levels in six out of the 23 animals treated i.v., and, therefore, model-independent kinetic parameters were utilized for evaluating age-dependent pharmacokinetics of OTC. In the 3-week-old calves, the total body clearance (ClB) was 0.0022 ml/min/kg, the total distribution volume (Vd area) was 2.48 l/kg, and the distribution volume of the central compartment (V1) was 0.56 l/kg. Mean values for ClB, Vd area, and V1 in 3-week-old calves were two-, three- and four-fold greater, respectively, than the corresponding values in cows. Mean values of ClB and Vd area for the 12- and 14-week-old calves were intermediate between the corresponding values in 3-week-old calves and cows. Dose and state of lactation did not affect the model-independent parameters. The i.v. and i.m. data illustrated that the recommended dose levels of OTC in young calves should be twice those employed in cows for obtaining similar plasma OTC concentration--time profiles.

Age Factors↗
PubMed1983

Influence of intramammary infusion of polymyxin B on the clinicopathologic course of endotoxin-induced mastitis.

The influence of giving 1 dose of polymyxin B (1.6 X 10(6) U/quarter) by the intramammary route to dairy cows to modify the clinicopathologic course of mastitis induced by intramammary infusion of Escherichia coli endotoxin (1 mg/quarter) was examined. Pretreatment with polymyxin B or its simultaneous administration reduced and delayed the typical febrile and leukopenic responses to endotoxin infusion, prevented an increase in plasma lactate dehydrogenase activity and a reduction in plasma zinc concentration, but only marginally influenced the degree of udder inflammation and had no effect on leukocytosis in the milk. Intramammary infusion of polymyxin B at 30 or 60 minutes after endotoxin was infused prevented the increase in plasma lactate dehydrogenase activity and moderated the decrease in plasma zinc concentration, but otherwise failed to alter the clinicopathologic course of endotoxin-induced acute mastitis.

Animals↗
PubMed1983

Indwelling jugular venous catheterization of semirestrained cattle.

An inexpensive method for chronic cannulation of one or both jugular veins in cattle was devised. A commercial catheter set containing a 14-gauge 5-cm needle, a 16-gauge 60-cm catheter with stylet, and a plastic retainer facilitated intravenous dosing and blood withdrawal at timed intervals. The method did not require special restraining equipment for large animals and was completed within 10 to 15 minutes per animal. The catheter apparatus did not interfere with ad libitum feeding and watering of trained cattle.

Animals↗
PubMed1982

Pharmacological aspects of chloramphenicol administration by the intramammary route to lactating dairy cows.

Concentrations of chloramphenicol (C M) were determined, by microbiological assay, in the milk and blood serum of 17 culled dairy cows after intramammary infusion of an approved parenteral CM product (Gloveticol) and in the milk of 16 lactating cows after treatment with two approved CM products for intramammary infusion, at dosages ranging from 1 to 30 g/cow. C M was quickly absorbed from the udder into the blood circulation; the doses of 12.5 and 25 g/cow were almost completely absorbed within 20 hours. Absorption half-life (t1/2ab) from fully functioning quarters was 57+/-18 minutes, and the t1/2ab from partially functioning quarters was 125+/-37 minutes. Mean peak serum C M concentrations were 6.1, 16.2, and 37.4 microg/ml after the cows had been infused with 5, 12.5, and 25 g, respectively. These values were considerably higher than the corresponding peak serum C M concentrations reported following intramuscular injection of equivalent doses of the drug. C M residues were not detectible microbiologically in milk from treated quarters 20 hours after treatment with 5 g or 6.25 g, and 36 hours after treatment with 15 g. Drug concentrations in the milk from the non-treated quarters were approximately 70 per cent of the corresponding serum drug levels. Serum CM concentrations of potential therapeutic value in the treatment of gram-negative bacterial infections, i.e. > 5 microg/ml, were maintained for 8 hours after cows had been infused with 12.5 g, and for 12 hours after infusion with 25 g. The implications of the improved systemic availability of C M infused by the intramammary route over the intramuscular route are discussed in terms of potential therapeutic efficacy, local irritation, and duration of drug residues.

Absorption↗
PubMed1982

Comparative plasma ampicillin levels and bioavailability of five parenteral ampicillin formulations in ruminant calves.

Plasma ampicillin concentrations were determined in an eight-ways crossover trial involving six ruminant calves, which were treated intravenously (i.v.) with sodium ampicillin at 15.5 mg/kg and intramuscularly (i.m.) with five different ampicillin trihydrate or ampicillin anhydrate formulations at 7.7 mg/kg. The mean plasma concentration-time curve (Cp) after intravenous ampicillin sodium administration was described biexponentially, as: Cp = 38.8 e -0.0268t + 0.45 e -0.0058t. Intramuscular injection, into the lateral neck, of Ampikel-20 and Polyflex resulted in 100 per cent bioavailabilities within 12 h post injection (p.i.), but the biological half-lives (t1/2) were different, being 2.1 and 3.8 h, respectively. Ampikel-20 produced the highest peak plasma drug concentrations (mean C max :4.8 microgram ampicillin/ml). After intramuscular injection of Penbritin the mean bioavailability for the first 12 h p.i. was 63 per cent, the mean t1/2 was 5.9 h, and the mean Cmax was 1.8 microgram/ml. Treatment with Albipen and Duphacillin resulted in low plasma ampicillin levels, which were maintained for 3 to 6 days p.i., limited bioavailability during the first 12 h p.i., and a mean t1/2 of 22.2 and 11.9 h, respectively. Plasma concentrations of ampicillin from four hours onwards after i.m. and s.c. administration of Ampikel-20 at a dose level of 15.5 mg/kg were similar. The duration of potentially therapeutic plasma ampicillin concentrations after administration of each formulation is presented. Pre-slaughter withdrawal times for diseased calves are suggested for the different formulations studied.

Ampicillin↗
PubMed1982

The pharmacokinetics and tissue levels of polymyxin B, colistin and gentamicin in calves.

Following a single intravenous injection of polymyxin B, colistin (5 mg/kg, each) and gentamicin (3 mg/kg) to calves, the decline in serum antibiotic concentration generally suggested a three-compartment (open system) pharmacokinetic model. Tissue binding is a dominant factor in the distribution and elimination kinetics of the drugs. Less than 65% of the dose of polymyxin B and colistin was recovered in the urine during 48 h after treatment. Concentrations of nonbound polymyxin B and colistin in the kidney, liver, lung, heart, and skeletal muscles were similar to total (free and bound) serum drug levels, but considerably higher concentrations were found, in bound form, in chloroform-ethanol extracts of these organs. At 24 h after treatment, more than 50% of the doses of polymyxin B and colistin were present bound to the tissues; the largest amount was in the skeletal muscles. Gentamicin was concentrated in the kidney, predominantly in the free form. At 48 h after treatment the amount of gentamicin in the kidney was 6.3% of the administered dose, being more than five times greater than the corresponding amounts of polymyxin B and colistin. The extent of tissue uptake of polymyxin B and colistin limits the usefulness of kinetic values, which are derived from the analysis of serum drug levels, for the purpose of designing dosage schedules. The strong affinity of the polymyxins to the muscle tissue, and gentamicin to the kidney, can result in drug residues persisting in the body for several weeks.

Animals↗
PubMed1982

Distribution of penicillin G, dihydrostreptomycin, oxytetracycline, and chloramphenicol in serum and subcutaneous chamber fluid.

Penetration of penicillin G, dihydrostreptomycin, oxytetracycline, and chloramphenicol into interstitial fluid of calves was estimated using subcutaneously implanted, multiple perforated spherical polypropylene capsules as a model. Antibiotic concentrations were determined in simultaneously withdrawn serum and capsular fluid (CF) samples at intervals after single and multiple intramuscular injections of antibiotics at recommended dose schedules. Peak concentrations of penicillin G in CF were 57% of those in serum, and the drug was eliminated from CF at a slower rate than from serum. Dihydrostreptomycin diffused into CF to a limited degree and was eliminated from CF much more slowly than from serum leading to gradual drug accumulation in CF upon repeated dosing. Multiple injections of oxytetracycline resulted in CF drug levels comparable with those in serum. Concentrations of chloramphenicol in CF were generally similar to free (non-protein bound) serum drug levels. CF concentrations of penicillin G were within the range of the minimal inhibitory concentrations of the drug for pathogenic gram positive micro-organisms and CF levels of dihydrostreptomycin, oxytetracycline, and chloramphenicol were apparently sufficient to inhibit the majority of gram negative pathogens involved in bovine injections. Advantages and limitations of the tissue cage model are briefly discussed.

Animals↗
PubMed1982

Pharmacokinetics of polymyxin B administered via the bovine mammary gland.

Polymyxin B was infused into normal, chronically inflamed, and acutely inflamed quarters of the mammary gland of lactating cows at dosages ranging between 1 and 2 million units (100-200 mg) per quarter. Samples of milk from treated and non-treated quarters, jugular venous blood, subcutaneous abdominal (mammary) venous blood, and urine were collected at intervals after treatment and were assayed using microbiological test methods for polymyxin B concentrations. The drug was not absorbed from normal and chronically inflamed quarters; more than 90% of the infused dose was recovered in milk within 24 h after treatment, and drug residues were detected up to the ninth milking. Drug concentrations in milk from acutely inflamed quarters were significantly lower than in milk from normal quarters; 55% of the infused dose was recovered in the milk within 24 h after treatment. The drug was detected in milk from non-treated quarters, in blood from the subcutaneous abdominal vein, and in the urine during 36-48 h after acutely inflamed quarters were infused with the drug. These data indicate that polymyxin B is well distributed throughout, and is absorbed to a significant degree into the systemic circulation from the acutely inflamed udder.

Absorption↗
PubMed1981

Comparative efficacy of three antibiotic products for the treatment and prevention of subclinical mastitis during the dry period.

The comparative efficacy of a product containing 500 mg benzathine cloxacillin (Orbenin D.C.). another product containing 100 mg nafcillin, 300 mg procaine benzylpenicillin and 100 mg dihydrostreptomycin (Nafpenzal D.C.) and a third product containing 250 mg cephalonium (Cepravin D.C.), in the elimination and prevention of mastitis due to gram-positive microorganisms during the dry period was investigated in 1253 cows located in 14 herds in Israël. Although more uniform results were observed after treatment with Nafpenzal D.C. differences among herds were rather large. The mean cure rate for Staphylococcus aureus quarter infections was 81.4 per cent. New S. aureus infections which occurred between drying off and post calving sampling time were found in 7.0 per cent of the quarters. Dry period therapy reduced infection level with S. aureus from 13.5 per cent of quarters to 8.0 per cent. A similar proportional decrease was found in infection level due to non-agalactiae Streptococcus quarter infections.

Animals↗
PubMed1981

Effect of Solcoseryl on the clinical course of experimental Escherichia coli-endotoxin mastitis.

Experimental Escherichia coli-endotoxin mastitis was induced in a single quarter in twenty-eight cows. The inflamed quarters of six of the cows were treated with 50 mg Solcoseryl infusion in an oil base starting 4-6 h after endotoxin infusion, and four additional infusions were given at 12-h intervals. The inflamed quarters of eight of the cows were similarly treated with 200 mg Solcoseryl whereas the remaining fourteen cows served as control. Solcoseryl treatment did not alter the systemic or local course of acute mastitis. Local reaction, as assessed by the California Mastitis Test (CMT), however, subsided considerably sooner in quarters treated with Solcoseryl, and the effect of Solcoseryl in hastening udder tissue repair processes appeared to be dose dependent. The 200 mg dose of Solcoseryl resulted in pre-endotoxin CMT scores as early as 6 days after endotoxin infusion.

Actihaemyl↗
PubMed1981

Experiments with the double isotope single-injection method for determining glomerular filtration rate and effective renal plasma flow in veal calves.

Single injections of the radiochemicals Cr51-EDTA and I125-ortho-iodohippurate (I125-OH) were used simultaneously to measure the glomerular filtration rate (GFR) and effective renal plasma flow (ERPF), respectively, in 26 calves weighing between 37 kg and 90 kg. The mean GFR was 2.31 ml per minute per kg and the mean ERPF was 9.62 ml per minute per kg. These values are very similar to the GFR and ERPF measured in young calves and adult cattle by using constant infusions of inulin and para-aminohippurate as marker substances. Correlation coefficients of the order of 0.70 were found between clearance values and body-weights. The method described is rapid and reliable.

Animals↗
PubMed1980

Preliminary clinical pharmacological investigations of tylosin and tiamulin in chickens.

The minimal inhibitory concentrations (MIC) of tiamulin and tylosin for mycoplasma, Gram-positive, and Gram-negative micro-organisms isolated from chickens were determinated by the agar dilution method. Median MIC values for tiamulin against Mycoplasma gallisepticum (0.05 microgram/ml) and Mycoplasma synoviae (0.10 microgram/ml) were 2 to 4 times lower than the corresponding values for tylosin. Tiamulin was also slightly more effective in vitro in inhibiting Escherichia coli, Pasteurella multocida, and beta-haemolytic streptococci than was tylosin. Groups of chicken were offered tiamulin medicated drinking water at rates of 125 and 250 mg/litre for 48 hours. Average serum tiamulin concentrations were 0.38 and 0.78 microgram/ml, respectively. When tylosin tartrate was added to the drinking water at 500 and 700 mg/litre, average serum drug levels were 0.12 and 0.17 microgram/ml, respectively. Tiamulin was 45% bound in chicken serum, as against 30% serum protein binding for tylosin. Correlations were made between free (non protein bound) serum drug levels and the MIC values of the two drugs. Such comparisons suggest that when tiamulin is given in the drinking water at rates of 125 to 250 mg/litre, better antimycoplasmal activity is to be expected in vivo than by giving tylosin tartrate in the drinking water at 500 to 700 mg/litre. Based on these data, no clinical efficacy of these dose rates can be expected in flocks infected by gram-negative micro-organisms such as E. coli or P. multocida. The tylosin tartrate rate of 500 to 700 mg/litre, may be clinical ineffective the treatment of Staphylococcus aureus infections.

Animals↗
PubMed1980

Drug selection and use in mastitis: systemic vs local therapy.

The optimal properties of antibacterial drugs, (administered parenterally or intracisternally during clinical mastitis) required for achieving and maintaining effective drug concentrations at the site of infection are reviewed. The in vitro sensitivity of the udder pathogen, expressed as the minimal inhibitory concentration (MIC) of the drug, and the physicochemical properties of the antibiotic are major determinants in the duration of effective drug concentrations in the udder. Injectable oxytetracycline and chloramphenicol possess limited IM bioavailability properties, and therefore, should be administered IV. Effective passage of drug from blood into the udder is best achieved with the macrolide antibiotics, but the antibacterial spectra of these drugs are limited to gram-positive pathogens. For intramammary treatment, drugs that are distributed throughout the udder and are quickly absorbed into the general blood circulation should be preferred. A second priority should be given to those drugs possessing more limited distribution characteristics. Some of the most active drugs in vitro are poorly and unevenly distributed in the udder and are absorbed only to a limited extent.

Animals↗