Disposition of oxytetracycline in pigs after i.m. administration of two long-acting formulations

Two commercially available long-acting oxytetracycline (OTC) formulations were administered by the intramuscular (i.m.) route to six healthy pigs at the recommended dose of 30 mg/kg. After 2 h the mean maximum concentration (C(max)) reached values of 8.1 +/- 2.2 and 15.4 +/- 11.1 microg/mL, respectively. These concentrations remained higher than 0.5 microg/mL for more than 5 days after drug administration. The area under the concentration time curve (AUC09 days) of each formulation was 255 +/- 76.5 and 399.2 +/- 123 microg. h/mL, respectively, and the mean residence time (MRT) was around 3 days for both formulations. No significant differences were observed between the pharmacokinetic parameters of the two formulations, showing the bioequivalence of the two formulations studied according to the criteria established by the Food and Drug Administration (FDA) and the Committee for Veterinary Medicinal Products (CVMP).     

Use of long-acting oxytetracycline against pasteurellosis in lambs

The efficacy of long-acting oxytetracycline in the control of pneumonic pasteurellosis in lambs was tested on seven Scottish farms. After laboratory confirmation of pasteurella-related deaths in lambs, half the lambs in each flock were given long-acting oxytetracycline (20 mg/kg intramuscularly) and half were left untreated. On three farms a single treatment was given and on four farms two doses were administered four days apart. Eighteen of the 878 control lambs died as a result of confirmed Pasteurella haemolytica pneumonia compared with one of the 878 treated lambs. In addition nine of the control lambs were diagnosed clinically to have pasteurellosis which responded to treatment with oxytetracycline. None of the treated lambs were seen to be ill during the trial.     

长效土霉素注射液的研究进展

综述了土霉素注射液在处方、局部刺激和局部残留、药代动力学、生物药剂学和在动物体内残留等方面的研究进展。     

Cure of Dermatophilus congolensis infection in cattle by long-acting oxytetracycline

Under conditions simulating traditional husbandry, a single intramuscular dose (20 mg/kg) of long-acting oxytetracycline was efficacious in treating different grades of bovine dermatophilosis. There was complete healing in 26 out of 28 animals (93 per cent) within four weeks. By contrast, only four out of 11 animals treated with penicillin (70,000 iu/kg) plus streptomycin (70mg/kg) were apparently cured and three relapsed within one month. No spontaneous recoveries were observed among 18 untreated animals. In the group treated with oxytetracycline, two, in the penicillin plus streptomycin, seven, and in the untreated control group, 11 animals died of the disease.     

Efficacy of parvaquone and long-acting oxytetracycline in Theileria annulata infection

Therapeutic and prophylactic efficacies of parvaquone and long-acting oxytetracycline were tested against Theileria annulata infection, induced by injecting a suspension of infected ground tick tissues (GUTS) into groups of 4 or 5 calves. This infection killed two of four control calves, while all the animals given a single intramuscular dose of 20 mg kg-1 parvaquone or long-acting oxytetracycline on the day of infection underwent mild reactions and recovered. Two separate doses of parvaquone of 10 mg kg-1 administered on the first and second days of fever protected four out of five calves. All the recovered animals from both treated and control groups resisted a homologous challenge with GUTS on Day 45 post-infection which killed three out of four susceptible unimmunized control calves.     

Chemoprophylaxis of Anaplasma ovis infection in sheep with a long-acting oxytetracycline

The chemoprophylactic efficacy of long-acting oxytetracycline was determined in 13 susceptible ewes infected with Anaplasma ovis. The drug was administered intramuscularly at a dose rate of 20 mg kg-1 body weight during the prepatent period. When the ewes were exposed to an equivalent homologous challenge on Day 45 post-infection, each showed a mild or inapparent reaction. The host reactions, i.e., body temperature, parasitaemia, packed-cell volume (PCV), haemoglobin, humoral and cell mediated immunity (CMI) were also studied. The results indicate that the use of oxytetracycline during the incubation period would minimise clinical signs of an Anaplasma infection; this may be due to an increasing CMI response.     

Efficacy of long-acting oxytetracycline for the prevention of tick-borne fever in calves

Twenty-six calves which had not previously grazed tick-infested pasture were divided into two equal groups. On May 26, 1988 (day 0) they were turned out into a field of rough grazing where cases of redwater fever had occurred the previous spring. Seven, 14, 21 and 28 days after the start of the trial the animals in one group each received an intramuscular injection of 20 mg/kg bodyweight of long-acting oxytetracycline. During the 60 days of the trial the animals received a severe tick-borne fever challenge, in some cases combined with a redwater fever challenge. An unforeseen complicating factor was the presence of animals persistently infected with bovine viral diarrhoea virus, present in almost equal numbers in both groups. At the end of the trial the treated group weighed on average 16 kg more than the control group, a difference which was attributed to the suppression of tick-borne fever by oxytetracycline.     

Treatment of Moraxella bovis infections in calves using a long-acting oxytetracycline formulation

George, L.W. & Smith J.A. Treatment of Moraxella bovis infections in calves using a long-acting oxytetracycline formulation. J. vet. Pharmacol. Therap. 8, 55–61.
Studies were undertaken to determine the effectiveness of an oxytetracycline HCl formulation for the prophylaxis and treatment of chronic Moraxella bovis ocular infections in calves. Two separate experiments were performed. For the first, calves were separated into two groups and the eyes were infected with M. bovis. The eyes of these calves were observed and cultured for 37 consecutive days. On the 37th and 40th day, each of the five calves were treated intramuscularly with the drug (20 mg/kg of body weight). The other five calves (second group) remained untreated as controls. The cultures from the five treated calves were negative after the first antibiotic administration and remained so for 14 days. M. bovis was isolated from each eye of the control calves at least once during that time. None of the antibiotic-treated calves was completely resistant when reinfected with M. bovis. For the second experiment, calves were given a prophylactic administration of the formulation and were then infected with M. bovis 48 ( n = 4 calves) or 72 ( n = 4 calves) h later. These treatments resulted in a lower incidence of keratoconjunctivitis and a decreased duration of bacterial shedding, as compared to controls ( n = 8 calves), but did not completely prevent the occurrence of disease or the establishment of ocular infections.
Lisle W. George, Department of Medicine, School of Veterinary Medicine, University of California, Davis, CA 95616, U.S.A.     

Pharmacokinetics and local tolerance of a long-acting oxytetracycline formulation in camels.

Disposition and local tolerance of a new oxytetracycline (OTC) long-acting formulation were evaluated in camels by measuring the dynamics of creatine kinase. Six camels (Camelus dromedarius) were administered OTC by IV and IM routes according to a 2-period cross-over, study design. Serum OTC concentration was measured, using a microbiological assay procedure. After IV administration (5 mg/kg of body weight), mean residence time was 7.7 +/- 2.8 hours, steady-state volume distribution was 706.1 +/- 168.6 ml.kg-1 and serum clearance was 75.3 +/- 23.2 ml.kg-1.h-1. After IM administration of the long-acting OTC formulation (10 mg/kg), maximal OTC concentration (3.49 +/- 0.44 micrograms.ml-1) was observed after 7.3 +/- 3.5 hours; the mean systemic availability was near 100%, and serum concentration greater than 0.5 micrograms.ml-1 was maintained for about 72 hours. After IM administration, mean control serum activity of creatine kinase was multiplied by a factor of 3.36 +/- 1.55; at 72 hours after OTC administration, the serum creatine kinase activity returned to control values. It was concluded that OTC is an antibiotic of potential interest in camels and that a dosage regimen of 10 mg.kg-1 deserves attention when using a long-acting formulation that has good local tolerance and near total systemic availability.     

Potential use of long-acting injectable oxytetracycline for treatment of chlamydiosis in Goffin's cockatoos

To determine the potential use of parenteral therapy in the treatment of chlamydiosis in psittacine birds, the disposition and toxicity of a long-acting oxytetracycline (OTC) was evaluated in Goffin's cockatoos. Following intramuscular and subcutaneous administration of 50 to 100 mg/kg body weight, plasma OTC concentrations of 7 to 15 micrograms/ml were obtained 3 hr following injection and declined with a terminal half-life between 8.9 to 14.7 hr. Plasma concentrations in excess of 1.0 microgram/ml were maintained for 48 to 68 hr. Multiple-dose treatment of 100 mg/kg subcutaneously every 3 days for 30 days caused focal necrosis and scabs at the injection site but no other clinical or serological evidence of adverse effects. Long-term treatment did not result in accumulation or alteration in the disposition of OTC. Based on this study, a dosage regimen of 50 to 100 mg/kg of OTC subcutaneously every 2-3 days would safely maintain plasma concentrations in excess of 1.0 microgram/ml and could potentially be used as an alternative to medicated feeds or daily oral dosing regimens for the treatment of chlamydiosis in psittacine birds.     

Comparison of pharmacokinetic parameters for two oxytetracycline preparations in pigs

Pharmacokinetics of oxytetracycline (OTC) were studied in 10 pigs after administration of 20 mg/kg body weight of either a conventional (OTC-C) or a long-acting (OTC-LA) preparation.
After intravenous administration of OTC-C the elimination half-life for OTC was 3.75 h, with approximately 75% of the dose being excreted in the urine in 1 week. Intramuscular (i.m.) injection of OTC-C resulted in plasma peak values after 4 h, while OTC-LA after i.m. administration produced the highest plasma levels within 1 h, although these were lower than with OTC-C.
For both preparations the bioavailability after i.m. administration was 95–100% and about 70% of the dose was excreted in the urine during the first week.
With OTC-C given i.m., plasma concentrations above 0.5 μg/ml were maintained for 28 h and with OTC-LA for 35 h indicating a weak retard effect of the latter.
Pronounced tissue damage at the injection site was seen 1 and 2 weeks after the administration of OTC-LA, while OTC-C produced very little irritation. OTC could be found at the injection site for 2 weeks, the concentrations being higher for OTC-LA than for OTC-C.