Oxidation and O-dealkylation of sulphamonomethoxine by the turtle Pseudemys scripta elegans

Sulphamonomethoxine is O-demethylated at the 6 position and oxidised at the 2 position of the pyrimidine substituent by Pseudemys scripta elegans. No N4-acetylation takes place. The yield of the oxidation reaction is twice that of the O-demethylation reaction.

O-demethylation and N4-acetylation of sulphadimethoxine by the turtle Pseudemys scripta elegans

After an oral dose of 350 mg of sulphadimethoxine, the turtle Pseudemys scripta elegans O-dealkylates sulphadimethoxine at the 2- and 6-position at 38% and 19% respectively, the 2-position being favoured. Acetylation of sulphadimethoxine and its hydroxy metabolites occurs for 57.4%.

Comparative pharmacokinetics of oxytetracycline in rainbow trout (Salmo gairdneri) and African catfish (Clarias gariepinus)

A comparative pharmacokinetic study was conducted in rainbow trout (Salmo gairdneri) and African catfish (Clarias gariepinus) following intravenous (i.v.) and intramuscular (i.m.) administration of oxytetracycline (OTC) at a dose rate of 60 mg/kg body weight. Trout and catfish were kept in aerated tap water in tanks at constant temperatures of 12 degrees C and 25 degrees C, respectively. The two- and three-compartment open models adequately described plasma drug disposition in African catfish and rainbow trout respectively, following i.v. OTC administration. Compared to catfish (COP = 86 +/- 10 micrograms/ml) an eightfold higher extrapolated zero time concentration was obtained in trout (COP = 753 +/- 290 micrograms/ml). A significant difference was observed with respect to the relatively large apparent distribution volumes (Vd(area] after i.v. OTC administration (trout, mean value: 2.1 l/kg; catfish, mean value: 1.3 l/kg). The mean final elimination half-lives of both fish species were greater than previously reported in mammals (trout, 89.5 h; catfish, 80.3 h). A mean maximum plasma concentration (Cmax = 56.9 micrograms/ml) was obtained in trout at 4 h after i.m. administration of OTC. In catfish a lower Cmax of 43.4 micrograms/ml was determined at about 7 h. No significant difference was observed with respect to bioavailability following i.m. administration of OTC (trout, 85%; catfish, 86%).

Pharmacokinetics and renal clearance of sulphadimidine, sulphamerazine and sulphadiazine and their N4-acetyl and hydroxy metabolites in pigs

The effect of molecular structure on the drug disposition and protein binding in plasma, the urinary recovery, and the renal clearance of sulphamerazine (SMR), sulphadiazine (SDZ), and sulphadimidine (SDM) and their N4-acetyl and hydroxy derivatives were studied in pigs. Following IV administration of SDM, SMR and SDZ, their mean elimination half-lives were 12.4 h, 4.3 h and 4.9 h respectively. The plasma concentrations of parent sulphonamide were higher than those of the metabolites, and ran parallel. The acetylated derivatives were the main metabolites; traces of 6-hydroxymethylsulphamerazine and 4-hydroxysulphadiazine were detected in plasma. The urine recovery data showed that in pigs acetylation is the major elimination pathway of SDM, SMR and SDZ; hydroxylation became more important in case of SMR (6-hydroxymethyl and 4-hydroxy derivatives) and SDZ (4-hydroxy derivatives) than in SDM. In pigs methyl substitution of the pyrimidine side chain decreased the renal clearance of the parent drug and made the parent compound less accessible for hydroxylation. Acetylation and hydroxylation speeded up drug elimination, because their renal clearance values were higher than those of the parent drug.

N-oxidation, O-demethylation, and excretion of trimethoprim by the turtle Pseudemys scripta elegans

Trimethoprim was excreted within one hour after being given orally to the turtle Pseudemys scripta elegans. No O-demethylated or N-oxide metabolites were detected.

O-demethylation and N4-acetylation of sulfadimethoxine by the snail Cepaea hortensis

The snail Cepaea hortensis O-dealkylates sulfadimethoxine at the 2- and 6-position, the 2-position being favoured. Sulfadimethoxine is also acetylated, while no measurable acetylation of the hydroxy (= demethyl) metabolites took place.

Oxidation and acetylation of sulfamonomethoxine by the snail Cepaea hortensis

Sulfamonomethoxine is not O-demethylated in the snail Cepaea hortensis, but acetylated (15.2%) and oxidised (0.78%) at the 2 position of the pyrimidine nucleus.

Pharmacokinetics and metabolism of sulphadimidine in kids at 12 and 18 weeks of age

The pharmacokinetics and metabolism of sulphadimidine (SDM) following intravenous administration of 100 mg/kg were studied in seven dwarf preruminant kids at 12 weeks of age, and again at the ruminant stage, when the animals were 18 weeks old. The persistence of SDM in 18-week-old kids was prolonged in comparison to the 12-week-old animals: a lower total body clearance and a prolonged elimination of SDM were obtained in the older animals. The renal clearance values of SDM and its metabolites were the same at both ages. The decrease of SDM clearance is related to the significant reduction in SDM hydroxylation at the older age. The reduced oxidative hepatic metabolism may result from the sexual maturation of the kids.

Pharmacokinetics, metabolism and renal clearance of sulphatroxazole in calves and cows

The pharmacokinetic analysis of plasma concentration--time curves after a single i.v. dose of 20 mg/kg sulphatroxazole (STZ) to calves and cows revealed a small distribution volume of STZ (mean VD(area) = 0.22-0.26 l/kg) and an age dependent elimination (mean t1/2 6.6-18.8 h). In calves and cows, STZ was extensively metabolized into the N4-acetyl and 5-hydroxy derivatives. In the plasma of calves, the N4-acetyl metabolite (N4-STZ) was present in greater amounts than the hydroxy metabolite (5-OH-STZ), while in cows' plasma concentration of these two metabolites were similar. In the milk of dairy cows STZ concentrations paralleled those of the metabolites and were approximately 21 times lower than corresponding plasma concentrations. The mean plasma protein binding of STZ and its metabolites ranged from 36.4 to 82.5% of total concentration. The N4-STZ derivative was excreted by tubular secretion; the 5-OH-STZ and the parent compound, mainly by glomerular filtration. In calves the majority of STZ administered was excreted as N4-STZ (40-52%), while in cows the parent drug dominated the urinary excretion (36%).

Effect of tick-borne fever (Ehrlichia phagocytophila) and trypanosomiasis (Trypanosoma brucei 1066) on the pharmacokinetics of sulfadimidine and its metabolites in goats

The effect of tick-borne fever (TBF) and trypanosomiasis (TBR) on the plasma disposition of sulfadimidine (SDD) in goats was studied after iv administration of 20 and 200 mg/kg of body weight. In each group of six goats, the plasma disappearance curves showed four animals with rapid and two with slow SDD elimination. It is likely that this difference is determined by oxidative rather than acetylation phenotype. In all goats administered 20 mg/kg, half-life increased with TBF but not with TBR. Vd(beta) decreased with both infections. With 200 mg/kg, Vd did not change, whereas AUC and MRT increased with both infections. Metabolites were examined in TBF experiments: N4-acetyl-SDD (N4Ac), 6-hydroxymethyl-SDD (CH2OH) and its glucuronide, 5-hydroxy-SDD (SOH) and its glucuronide, and 6-carboxy-SDD (COOH) and its glucuronide (COOH-glu). At low dose (20 mg/kg), TBF caused the proportion of dose recovered from urine as unchanged SDD to be halved, whereas N4Ac increased correspondingly (2x). After the high dose (200 mg/kg), elimination was saturated and changes in proportional recovery of SDD in urine were less. However, the N4Ac proportion was still doubled, in contrast to the other metabolites, suggesting that saturation was caused by oxidations rather than by acetylation. Formation of CH2OH was the same in health and disease after the low dose, but glucuronidation dropped from 20% to 4% (rapid) or 7% (slow) of total CH2OH.(ABSTRACT TRUNCATED AT 250 WORDS)

Excretion and metabolism of a series of xanthines by the turtle Pseudemys scripta elegans

The xanthines paraxanthine, xanthine, and uric acid are absorbed completely by the turtle Pseudemys scripta elegans and metabolised presumably into CO2 and NH3. No intermediate metabolites are excreted. Caffeine, hydroxycaffein, theobromine, hydroxytheobromine, and hydroxypraxanthine are absorbed and excreted in different amounts or percentages of the dose administered. Intermediate metabolites of these compounds are not excreted. The turtle Pseudemys scripta elegans may, therefore, be ammonotelic.

N-oxidation, N-demethylation, and excretion of pefloxacin by the turtle Pseudemys scripta elegans

Pefloxacin is minimally absorbed by the gastrointestinal tract of the turtle Pseudemys scripta elegans and then N-oxidised and N-demethylated. Pefloxacin is excreted within one hour after being given orally to the turtles.

Monitoring milk for chloramphenicol residues by an immunoassay (Quik-card)

An easy to perform immunoassay method (Quik-card) for monitoring milk on the presence of chloramphenicol residues exceeding 5 to 10 ppb is described, as well as an extraction and preconcentration method utilising a Sep-pak silica cartridge, which enables the detection of CAP residues in milk in concentrations exceeding 1 ppb by HPLC and 0.1 ppb by the immunoassay.

Pharmacokinetics, renal clearance and metabolism of ciprofloxacin following intravenous and oral administration to calves and pigs

The pharmacokinetics of ciprofloxacin, a quinoline derivative with marked bactericidal activity against gram-negative bacteria, was studied in calves and pigs following intravenous and oral administration. Ciprofloxacin was rapidly and well distributed in the body, exhibited a short elimination half-life of 2.5 h in both species, and was rapidly absorbed after oral administration (Tmax:2 to 3 h). The oral bioavailability in calves was 53 +/- 14% and for 1 pig 37.3%. The renal clearance of the unbound ciprofloxacin for both species was of the same order, indicated a predominantly tubular secretion pattern, and accounted for about 46% of the total drug elimination. No complete drug mass balance could be demonstrated. Small amounts of two metabolites were detected in the urine of calves, but not in pig urine.

Pharmacokinetics of ciprofloxacin in carp, African catfish and rainbow trout

The plasma disposition of ciprofloxacin was studied in carp, African catfish and trout after intravenous (IV) and intramuscular (IM) administration at a dose rate of 15 mg/kg. Pharmacokinetic analysis of IV data showed that ciprofloxacin was well distributed (distribution volume Vd(area): 3.08-5.59 litre/kg) and exhibited a similar elimination half-life of about 14 h in these 3 fish species. After IM administration to carp and trout a rapid absorption was noticed; the maximum ciprofloxacin plasma concentrations (mean: 3.49 and 2.37 micrograms/ml, respectively), were achieved within 1 h after injection. At the dose level applied, ciprofloxacin has potential therapeutic value for 2-5 days especially against gram-negative bacterial fish pathogens.

Pharmacokinetics, metabolism, and renal clearance of sulfadiazine, sulfamerazine, and sulfamethazine and of their N4-acetyl and hydroxy metabolites in calves and cows

The effect of molecular structure on the drug disposition and protein binding in plasma and milk, the urinary recovery, and the renal clearance of sulfadiazine, sulfamerazine, and sulfamethazine and of their N4-acetyl and hydroxy derivatives were studied in calves and cows. Sulfadiazine was highly acetylated and was slightly hydroxylated. Sulfamerazine and sulfamethazine were hydroxylated predominantly at the methyl group of the pyrimidine side chain; hydroxylation of the pyrimidine ring itself was more extensive for sulfamethazine than for sulfamerazine. At dosages between 100 and 200 mg/kg of body weight, sulfamethazine had a capacity-limited elimination pattern, which was not observed for sulfadiazine or sulfamerazine. The concentrations of the parent sulfonamide and its metabolites in plasma and milk were parallel, the latter being lower. Metabolite concentrations in milk were at least 8 times lower than those of the parent drug. Metabolism speeds drug elimination, producing compounds with renal clearance values higher than those of the parent drug. The effect on the metabolism and renal clearance of methyl substitution in the pyrimidine side chain is discussed.

The effect of testosterone and rutting on the metabolism and pharmacokinetics of sulphadimidine in goats

After testosterone pretreatment of castrated goats and during the rutting season of adult entire male goats, the oxidative metabolism of sulphadimidine (SDM) was inhibited markedly compared with the castrated control state of these animals. The oxidation of the 5 position (yielding 5-hydroxysulphadimidine) and of the 6-hydroxymethyl group (yielding 6-carboxysulphadimidine) was decreased equally, with that of the methyl group at the pyrimidine side chain itself being 6-hydroxymethylsulphadimidine (CH2OH), whereas the acetylation pathway was unaffected by testosterone. The consequence of altered metabolism by testosterone was a prolongation of SDM presence in the body. Effects on protein binding of the CH2OH metabolite and on the renal clearance of SDM were also investigated.

[The New Dutch Kidney Test. III. Practical evaluation]

The New Netherlands Kidney Test (NNKT) is a method used to detect residues of antibacterial agents in slaughtered animals. This test will shortly be substituted for the current Netherlands Kidney Test (NKT). The new method was tested for its suitability in meat inspection in the field by four district laboratories, comparative studies with the current Netherlands Kidney test being done at the same time. These investigations showed that, when the new test (NNKT) was used, 5.3 per cent of the category of diseased animals and, using the current Netherlands Kidney Test, 2.2 per cent of these animals were positive. When control discs were used, it was shown that reproducibility of the new test (NNKT) within and between the participating laboratories was satisfactory. A method was developed to obtain similar results on re-examination with the NNKT as those obtained in the first inspection. By freezing the duplicate discs at the time of performance of the test and using these discs for re-inspection, reproducible results were obtained with the NNKT. The substance inhibiting the growth of bacteria was identified in a number of specimens diagnosed as positive when the NNKT was used. False-positive results were not recorded in the NNKT.

[The New Dutch Kidney Test. II. Sensitivity of the test system]

When the in vitro sensitivity of the New Netherlands Kidney Test (NNKT) is compared with that of the test plates of the current Netherlands Kidney Test (NKT) and the EEC four-plate system (ECT), this shows that it occupies a middle position with regard to aminoglycosides, macrolides and tetracyclines. The test plate of the NNKT is more sensitive to sulphonamides. Experimental qualitative and quantitative studies in slaughtered pigs showed that the New Netherlands Kidney Test was equally sensitive or more so in detecting residues of sulphonamides, chloramphenicol, tetracyclines, aminoglycosides and penicillin derivatives than the ECT system for meat. In addition to the simplicity of the current Netherlands Kidney Test, the New Netherlands Kidney Test also shows the broad-spectrum sensitivity of the ECT system. When tolerance standard of nitrofurans or chloramphenicol respectively is 1 or 10 ppb, the New Netherlands Kidney Test will fail.

Effect of induced synovial inflammation on pharmacokinetics and synovial concentration of sodium ampicillin and kanamycin sulfate after systemic administration in ponies

Single doses of sodium ampicillin (10 mg/kg) and kanamycin sulfate (5 mg/kg) were administered intramuscularly (i.m.) separately, and then together, to five pony mares. The plasma antibiotic concentration-time curves were constructed. The pharmacokinetic parameters of the antibiotics given separately were not altered by concurrent administration. Four of the five pony mares were then given the i.m. kanamycin/ampicillin combination 4 h after acute synovitis and fever had been induced by injection of lipopolysaccharide into the left intercarpal joint. The plasma concentration-time curves and the synovial concentration-time curves of inflamed and normal joints were constructed. The Cmax of ampicillin in the lipopolysaccharide experiment was significantly higher than in the other experiments. The antibiotics entered the synovial fluid of the inflamed joints more quickly and attained higher concentrations than in the uninflamed joints. The ampicillin concentration exceeded 5 micrograms/ml in inflamed synovial fluid for some 2.5 h after injection, and kanamycin sulfate concentration exceeded 2 micrograms/ml for 7 h.

[The New Dutch Kidney Test. I. Description of the method]

The New Netherlands Kidney test is designed for the detection of antibacterial residues in slaughtered animals. It is a single-plate system in which the culture medium used is composed of Standard II nutrient agar, supplemented with 1 per cent of NaCl, 1 per cent of dextrose, 0.2 per cent of KH2PO4 and 0.28 per cent of Na2HPO4.12H2O. After autoclaving, this medium is cooled to 55 degrees C, which is followed by the addition of trimethoprim (0.12 microgram/ml of agar) and spores of Bacillus subtilis BGA (10(4) ml of agar). The pH should be adjusted to 7.00 +/- 0.05, the prepared medium then being poured out into plates specially designed for this purpose, in such a manner that the thickness of the layer of agar is 2.2 mm throughout. The following method is used in examining slaughtered animals for the presence of residues showing antibacterial activity. Four paper discs are placed in the renal pelvis for a minimum period of thirty minutes; two discs impregnated with fluid from the renal pelvis are frozen at -20 degrees C for possible re-inspection and the other two are laid diagonally on a test plate. 25 microliter of a trimethoprim solution (containing 2 micrograms of TMP per ml of a 10 per cent NaCl solution) are dropped on each of the two last-named discs. The test plates are incubated at 37 degrees C for a period ranging from thirteen to eighteen hours.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma disposition and renal clearance of sulphadimidine and its metabolites in laying hens

Plasma disposition of sulphadimidine (SDM) and its metabolites was studied in laying hens after 100 mg SDM kg-1 doses were administered as a single intravenous dose, a single oral dose and multiple oral doses once daily for five consecutive days. SDM was extensively metabolised by acetylation and hydroxylation. In plasma, the metabolite observed with the highest concentration was N4-acetylsulphadimidine (N4-SDM) followed by hydroxymethylsulphadimidine (CH2OH) and 5-hydroxysulphadimidine. Following intravenous administration a biphasic elimination (as seen for a capacity limited reaction) pattern for SDM and its metabolites was observed. Multiple (5x) SDM dosing revealed plasma SDM concentrations ranging between 7 and 108 micrograms ml-1; within 96 hours of termination of the multiple SDM dosing, the plasma SDM concentration was below 0.01 micrograms ml-1. The renal clearances of N4-SDM and the hydroxy metabolites were approximately 10 times greater than that of SDM. The SDM mass balance (faecal/urinary recovery) showed a loss of 56 per cent after intravenous dosage and of 67 per cent after a single oral dosage; the hydroxy metabolites accounted for the highest percentage in faeces/urine. Thus additional metabolic pathways must exist in laying hens.

[The predictive value of urinalysis in the New Dutch Kidney Test]

A urine test is described, by which a reliable indication of the time of slaughter is obtained in normal as well as in diseased animals, in which the New Netherlands Kidney Test (NNKT) will be negative. The test plate and testing procedure of the NNKT are used in this urine test.