Thiamphenicol pharmacokinetics in beef and dairy cattle.

The pharmacokinetics of thiamphenicol were investigated in 10 calves and six lactating cows. It was found that this drug is rapidly absorbed (15 min) following intramuscular injection with an absorption rate constant and a bioavailability of 8.7 h-1 and 84%, respectively. The drug appears to be widely distributed into various body fluids, yielding a volume of distribution (Vd(area) of approximately 0.9 l/kg. The micro-rate constants indicated that the antibiotic rapidly diffuses into the peripheral compartment (k12 > k21). Elimination from plasma is relatively rapid, with a biological half-life of about 1.75 h. Thiamphenicol appears shortly in milk (15 min) after its intravenous administration, and gives milk to plasma concentration ratios greater than one between 4 and 12 h.

Thiamphenicol pharmacokinetics in sheep.

The pharmacokinetics of thiamphenicol were investigated after intravenous (i.v.), intramuscular (i.m.) and oral (p.o.) administration to sheep. It was found that the drug is almost completely absorbed following intramuscular injection, with a bioavailability of about 87.5%. Thiamphenicol appears to be widely distributed into extravascular compartments, yielding a volume of distribution [V(b)] of approximately 1 l/Kg. Elimination from the blood is relatively rapid, with a biological half-life of about 1.5 h. Oral treatment showed that thiamphenicol is absorbed from the gastrointestinal tract yielding very low plasma concentrations which were maintained for at least 24 h. Although only 30% of the oral dose was systemically available, in contrast to chloramphenicol, thiamphenicol is truly absorbed when given orally to adult sheep. One possible reason for this observation is that rumen flora do not biotransform this drug as they do for chloramphenicol. Metabolism investigations are, however, needed to confirm this finding.

Pharmacokinetics and distribution of thiamphenicol in sheep given repeated intramuscular doses.

The pharmacokinetics of thiamphenicol and its distribution in various body fluids were studied after repeated intramuscular injection in clinically healthy adult Moroccan crossed Sardi-D'Man sheep. Thiamphenicol was rapidly absorbed from injection sites yielding peak plasma concentrations within 15-30 min. The elimination from the blood was also rapid, with a biological half-life of 1.51 +/- 0.51 h. The distribution pattern of thiamphenicol revealed that this antibiotic can penetrate many remote sites of the body. With the exception of the cerebrospinal fluid, concentrations of the drug in other body fluids were higher than the corresponding plasma concentrations.

Analysis of detomidine in horse blood, plasma and urine samples utilizing a sensitive gas chromatography-mass spectrometry method.

Chemical ionization- and electron impact ionization-selective ion monitoring provided a simple and sensitive method for measuring detomidine (Domosedan), a potent sedative-analgesic drug for horses and cattle. Chemical ionization was at least 10 times more sensitive than electron impact ionization. By using propranolol as an internal standard, we found that the recovery of detomidine from the extraction procedure used in this study was greater than 75% for plasma, whole blood, or urine samples. Approximately 68% of detomidine was bound to plasma protein and 53% was bound to red blood cells.

Central nervous system intoxications other than lead.

Other than lead, organophosphates and carbamates are probably the most important classes of toxicants affecting the central nervous system in food animals. Chlorinated hydrocarbons continue to present problems from time to time, as do certain poisonous plants. Less frequently encountered substances such as nitrofurans, certain rodenticides, herbicides, and other miscellaneous poisons are also discussed.

Fate of sodium pentobarbital in rendered products.

The fate of pentobarbital through rendering was evaluated by following a group of euthanatized animals through a commercial rendering facility. Samples of material were collected at various points in the rendering process, and assays for pentobarbital were conducted by an ultraviolet spectrophotometric method. The results indicated that the pentobarbital, or a closely related analogue, survived rendering without undergoing degradation. The pentobarbital was distributed approximately equally between the meat and bone meal and tallow fractions. If pentobarbital-euthanatized animals are processed along with other raw materials throughout a day's production, the likelihood of significant residues being present in rendered products is minimal.

Cacao bean shell poisoning in a dog.

Cacao bean shells contain potentially toxic quantities of theobromine, a xanthine compound similar in effects to caffeine and theophylline. A dog, which ingested a lethal quantity of garden mulch made from cacao bean shells, developed severe convulsions and died 17 hours later. Analysis of the stomach contents and the ingested cacao bean shells revealed the presence of lethal amounts of theobromine.

Oxytetracycline concentrations in healthy and diseased calves.

Pneumonia was induced in a group of calves that were then treated with oxytetracycline (OTC). When the plasma pharmacokinetics and tissue concentrations of this group were compared with those of healthy controls, obvious differences were observed. The volume of distribution and the half-life of OTC were increased in the group with pneumonia. Tissue concentrations of OTC (1.48 +/- 0.29 microgram/ml) were greater in the lungs of calves with pneumonia than that in the lungs (1.09 +/- 0.09 microgram/ml) of healthy controls. For the dose of OTC used, the correlation between serum concentration and tissue concentrations at 24 hours was poor. Seemingly, current concepts of antibiotic dosages and dosage intervals may be inadequate because they are based on blood and tissue values of healthy animals.

Plasma and tissue concentrations of oxytetracycline in the horse after intravenous administration.

Oxytetracycline (OTC) was administered IV to 3 clinically normal horses at a dosage of 10 mg of OTC/kg of body weight. Plasma OTC concentrations were determined at 30-minute intervals until postinjection minute (PIM) 240. At PIM 240, the mean OTC concentration in pulmonary tissue was 3.96 microgram/g of tissue (wet weight) and in renal tissue was 25.47 micrograms/g. diluted bronchial fluid had a mean concentration of 0.288 microgram of OTC/ml at PIM 240. The data demonstrated that OTC has adequate tissue distribution in horses.

Acute hepatic necrosis associated with the administration of mebendazole to dogs.

Mebendazole was administered to 7 adult Dachshunds and 2 adult Doberman Pinschers at 6-month intervals for routine parasite control. Two weeks after the 1st treatment, a 3-year-old Dachshund died of acute hepatic failure. Approximately 2 weeks following the 2nd treatment, two 5-year-old Dachshunds and one 3-year-old Dachshund had evidence of acute hepatic necrosis; 1 of these dogs died of fulminant hepatic failure. Typical clinical signs in affected dogs included anorexia, depression, vomiting, icterus, and hemorrhagic diarrhea. Two additional Dachshunds had biochemical evidence of hepatic dysfunction, ie. high serum alanine aminotransferase and serum alkaline phosphatase activities. One Dachshund and 2 Doberman Pinschers had no clinical or laboratory evidence of hepatic disease.

Ethylene glycol intoxication in ducks.

Ducks maintained over winter in an area used for automobile storage and repair were poisoned by anti-freeze. Signs were weakness, depression, ataxia, and death. Post-mortem lesions consisted of marked nephrosis; numerous oxalate crystals occluded the renal tubules. Levels of ethylene glycol were markedly elevated compared with levels in normal tissues. To further characterize the disease, six healthy ducks were given ethylene glycol in oral doses ranging from 1.1 to 17.8 ml/kg. As the dosage was increased, blood and tissue concentrations of ethylene glycol increased and time to death decreased. Histologic lesions were similar to those seen in the accidentally poisoned ducks.