Elimination of aminoglycoside antibiotics in milk following intramammary administration.

The elimination in cow milk of aminoglycoside antibiotic residues (neomycin, dihydrostreptomycin, kanamycin and gentamicin) was studied after intramammary administration of eight drug formulations marketed in France. Quantitative residue analysis was performed by a cylinder plate method. The sensitivity was 0.15 microgram/ml for neomycin, dihydrostreptomycin, kanamycin and 0.025 microgram/ml for gentamicin. The mean elimination periods ranged between 4 and 13 milkings. Several ways of assessing withdrawal times are discussed.

Residues of macrolide antibiotics in eggs following medication of laying hens.

1. The elimination kinetics of four macrolide antibiotics (tylosin, erythromycin, spiramycin and josamycin) in eggs were determined separately for albumen and yolk after oral administration through either drinking water or diet or after intramuscular injection. 2. Residues were assayed by a plate diffusion technique in cylinders with Micrococcus luteus as the test-organism. 3. Drug excretion was usually over a longer time in the yolk. Spiramycin was the most highly excreted in the egg whereas seven to eight times less tylosin and erythromycin was transferred. The conditions for the use of macrolide antibiotics in laying hens are discussed.

Sulphonamide residues in milk of dairy cows following intravenous injection.

An investigation was conducted into the elimination into milk of four sulphonamides (sulphadimidine, sulphamethoxypyridazine, sulphadimethoxine and sulphadoxine) after intravenous injections of drugs available in France. Sulphonamide determination in milk was performed using a high-performance liquid chromatography (HPLC) method with detection limit of 0.01 micrograms/ml. These results were used to determine the withdrawal times (two to six milkings) required for these drugs with a tolerance of 0.1 micrograms/ml as proposed by the European countries.

Excretion of tetracycline and chlortetracycline in eggs after oral medication of laying hens.

After dosing laying hens orally with tetracycline (TC) through either drinking water (0.25 and 0.5 g/l for 5 days) or feed (300 and 600 ppm for 7 days), and chlortetracycline (CTC) through feed (600 ppm) residues were determined by an agar plate diffusion technique in cylinders with Bacillus cereus as test-organism, separately for albumen and for yolk. The sensitivity threshold was 0.07 micrograms/g in albumen and 0.15 micrograms/g in yolk for TC and 0.01 micrograms/g in albumen and 0.06 micrograms/g in yolk for CTC. Drug excretion via egg was 3-fold higher for TC than for CTC. The drug was excreted preferentially into the yolk (about 75% of the total amount) and the elimination period lasted between 6 and 11 days for TC and 9 days for CTC, after treatment. Tetracycline use in laying hens is discussed, taking into consideration the proposals presented by the joint FAO/WHO Expert Committee on Food Additives.

Excretion of penicillins and cephalexin in bovine milk following intramammary administration.

The elimination into bovine milk of beta-lactam antibiotic residues (procaine penicillin G, cloxacillin, ampicillin, oxacillin, cephalexin) following intramammary administration of 10 preparations marketed in France was studied. The quantitative analysis of residues was carried out by a microbiological agar diffusion method using Bacillus stearothermophilus. Sensitivity ranged from 0.001 I.U./ml for procaine penicillin G and 0.001 micrograms/ml for ampicillin to 0.02 micrograms/ml for cephalexin. The mean periods of elimination on which withholding times are based were between four and seven milkings according to the drugs administered.

Excretion of oxytetracycline in eggs after medication of laying hens.

The kinetics of oxytetracycline elimination into eggs were determined separately for albumen and yolk after oral administration through either drinking water (0.1-0.25 and 0.5 g/l for 5 days) or feed (300 and 600 ppm for 7 days) or after intramuscular injections (3 X 15 mg/kg body weight and 3 X 30 mg/kg body weight), 24 hours apart. Residues were assayed by a microbiological agar diffusion method, with Bacillus cereus as test-organism. The detection threshold was 0.07 micrograms/g for albumen and 0.2 micrograms/g for yolk. In all cases, the elimination period lasted longer for the yolk; it varied between 0 and 10 days after treatment was discontinued, according to administration routes and dosages. The conditions of oxytetracycline utilization in laying hens are discussed. The oral route only might be used to adhere to the proposals presented by the Joint FAO/WHO Expert Committee on Food Additives.

[Elimination of polypeptide antibiotics (colistin and bacitracin) in the milk after intramuscular or intramammary administration]. / Elimination des antibiotiques polypeptidiques (colistine et bacitracine) dans le lait après administration intramusculaire ou intramammaire.

The elimination in cow's milk of polypeptidic antibiotic residues (colistin sulfate, colistin methanesulfonate and bacitracin) was investigated following intramuscular and intramammary administrations of eight drugs marketed in France. The quantitative analysis was performed according to the microbiological method of agar diffusion. The mean elimination periods lasted between three and six milkings for injected preparations, between four and six milkings for intramammary ones. These results were used as a basis to determine the withdrawal times required on these drugs. The problem of the diffusion of the residues into milk from a quarter treated by the intramammary route, to the untreated quarters was also addressed.

Excretion of penicillins in bovine milk following intramuscular administration.

The kinetics of elimination into milk of sodium penicillin G, procaine penicillin G, benzathine penicillin G, ampicillin and amoxycillin residues have been determined after intramuscular administration of eleven drugs chosen among those commercially available in France. These investigations will be used as a basis to estimate and harmonize the withdrawal times demanded for veterinary drugs. The quantitative analysis of residues was carried out by a cylinder plate microbiological method with Bacillus stearothermophilus as test organism. The threshold of detection is 0.001 unit (or micrograms)/ml of milk. The mean durations of elimination are four milkings for the association sodium penicillin G and procaine penicillin G, from seven to eight milkings for procaine penicillin G alone, from 19 to 33 milkings for benzathine penicillin G, and from three to five milkings for ampicillin and amoxycillin.