Comparison of the serum pharmacokinetics of a long acting and a conventional oxytetracycline injection

A crossover study was carried out in cattle to determine the serum pharmacokinetics of a standard dose (20 mg/kg bodyweight) of oxytetracycline given either as a conventional injectable formulation or as a long acting formulation. For reference purposes, an intravenous treatment (also given at 20 mg/kg) was included in the trial protocol. A comparison of the two treatment regimes showed that the long acting formulation gave a significantly lower peak oxytetracycline serum concentration, with a significant extension of drug serum concentration. The long acting formulation also showed a longer serum half life and a significantly greater area under the curve value, calculated from 36 hours onwards, together with serum oxytetracycline concentrations which exceeded 0.5 microgram/ml for 86.8 as opposed to 51.5 hours for the conventional formulation. It is concluded that the use of the long acting formulation in cattle leads to a more sustained serum oxytetracycline concentration than does the same dose of conventional formulation.     

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.     

Distribution of oxytetracycline into ocular tissues and tears of calves

A long-acting oxytetracycline formulation was administered (20 mg/kg of body weight) intramuscularly to calves, and the concentrations of the drug in serum, ocular tissues and tears were measured. The drug was distributed selectively to the epithelium of the conjunctiva and to the lacrimal gland ductules, and reached concentrations in each tissue that exceeded those in serum. The drug did not penetrate into the aqueous humour, and produced mean peak lacrimal fluid concentrations less than 1 microgram/ml after i.m. administration. When given subconjunctivally, however, concentrations greater than 2.0 micrograms/ml were observed in tears for 72 h. Severe local reactions occurred in all calves that were given the drug subconjunctivally.     

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.     

An evaluation of the relative efficacy of a new formulation of oxytetracycline for the treatment of undifferentiated fever in feedlot calves in western Canada

A field trial was performed under commercial feedlot conditions in western Canada to compare the efficacy of a new formulation of long-acting oxytetracycline (LA 30) to a standard long-acting oxytetracycline formulation (LA 20) and florfenicol (FLOR) for the treatment of undifferentiated fever (UF) in calves that received metaphylactic tilmicosin upon arrival at the feed-lot. Seven hundred and ninety-seven recently weaned, auction market derived, crossbred, beef calves suffering from UF were allocated to 1 of 3 experimental groups as follows: LA 30, which received intramuscular long-acting oxytetracycline (300 mg/mL formulation) at the rate of 30 mg/kg body weight (BW) at the time of allocation; LA 20, which received intramuscular long-acting oxytetracycline (200 mg/mL formulation) at the rate of 20 mg/kg BW at the time of allocation; or FLOR, which received intramuscular florfenicol administered at the rate of 20 mg/kg BW at the time of allocation and again 48 hours later. Two hundred and sixty-six animals were allocated to the LA 30 group, 265 animals were allocated to the LA 20 group, and 266 animals were allocated to the FLOR group. The relative efficacy of the LA 30 group, as compared with the LA 20 and FLOR groups, was assessed by comparing relapse, chronicity, wastage, and mortality rates. The overall mortality (RR = 0.50) rate in the LA 30 group was significantly (P < 0.05) lower than in the LA 20 group. However, the overall chronicity (RR = 2.56) and overall wastage (RR = 6.97) rates of the LA 30 group were significantly (P < 0.05) higher than in the LA 20 group. There were no significant (P > or = 0.05) differences in UF relapse rates or cause specific mortality rates between the LA 30 and LA 20 groups. In the economic analysis, there was an advantage of $28.59 CDN per animal in the LA 30 group compared with the LA 20 group. The overall chronicity (RR = 2.25) and overall wastage (RR = 2.80) rates of the LA 30 group were significantly (P < 0.05) higher than the FLOR group. There were no significant (P > or = 0.05) differences in UF relapse rates, overall mortality rates, or cause specific mortality rates between the LA 30 and FLOR groups. In the economic analysis, there was an advantage of $12.90 CDN per animal in the LA 30 group compared with the FLOR group. In summary, the results of this study indicate that it is more cost-effective to use a new formulation of long-acting oxytetracycline (300 mg/mL formulation administered at a rate of 30 mg/kg BW) than a standard long-acting oxytetracycline formulation (200 mg/mL formulation administered at a rate of 20 mg/kg BW) or florfenicol for the treatment of UF in feedlot calves that have previously received metaphylactic tilmicosin upon arrival at the feedlot.     

Vaccination of turkeys with cell-free culture filtrate of Pasteurella multocida

Turkeys given cell-free culture filtrate (CCF) of Pasteurella multocida strain R44/6 orally, via air sacs, or subcutaneously mixed 1:1 with incomplete Freund's adjuvant (IFA) at 6 and 9.5 weeks of age were compared with negative controls given bacteriologic medium and positive controls vaccinated with a commercial bacterin. At 13 weeks of age, serum antibody titers to P. multocida were detectable only in turkeys given CCF in IFA (low titers) and positive control turkeys (high titers), at which time turkeys were challenged orally with either the homologous strain or strain P-1059. Protection against challenge with strain R44/6 was provided by the commercial bacterin, CCF in IFA, and CCF given via air sacs. When turkeys were challenged with strain P-1059, protection was superior in turkeys given CCF via air sacs, intermediate in turkeys given commercial bacterin or CCF in IFA, and absent in negative control turkeys and turkeys given CCF orally. These results indicate CCF is an effective immunogen when administered via the lower respiratory tract for protecting turkeys against pasteurellosis.     

Pharmacokinetic disposition of a long-acting oxytetracycline formulation after single-dose intravenous and intramuscular administrations in the American alligator (Alligator mississippiensis).

The pharmacokinetics of a long-acting oxytetracycline preparation administered i.v. and i.m. to American alligators (Alligator mississippiensis) at 10 mg/kg was determined. Plasma levels of oxytetracycline were measured using high-performance liquid chromatography, and the resulting concentration versus time curve was analyzed using compartmental modeling and noncompartmental modeling techniques for i.v. and i.m. samples, respectively. A two-compartment model best represented the i.v. data. Intravenous administration of oxytetracycline resulted in an extrapolated mean plasma concentration at time zero of 60.63 +/- 28.26 microg/ml, with average plasma drug levels of 2.82 +/- 0.71 microg/ml at the end of the 192-hr sampling period. Plasma volume of distribution for i.v. oxytetracycline was 0.20 +/- 0.09 L/kg, with a harmonic mean elimination half-life of 15.15 hr and mean total body clearance rate of 0.007 +/- 0.002 L/hr/kg. Intramuscular administration of oxytetracycline achieved a mean peak plasma concentration of 6.85 +/- 1.96 microg/ml at 1 hr after administration, with average plasma drug levels of 4.96 +/- 1.97 microg/ml at the end of the 192-hr sampling period. The harmonic mean terminal elimination half-life for i.m. oxytetracycline was 131.23 hr. Based on the results of this study, long-acting preparations of oxytetracycline administered parenterally to American alligators at 10 mg/kg q 5 days is expected to maintain plasma concentrations above the minimum inhibitory concentration of 4.0 microg/ml for susceptible organisms.     

Characterisation of some Ornithobacterium rhinotracheale strains and examination of their transmission via eggs

The biochemical characteristics and antibiotic susceptibility of 12 Ornithobacterium rhinotracheale strains isolated from chickens and turkeys suffering from respiratory clinical signs and the survival of some isolates on egg-shell and within chicken eggs during hatching were examined. All O. rhinotracheale strains showed typical biochemical characteristics. Among the 16 drugs examined, penicillin G, ampicillin (MICs ranging from < or = 0.06 microgram/ml to 1 microgram/ml), ceftazidim (with MICs from < or = 0.06 microgram/ml to 0.12 microgram/ml), erythromycin, tylosin, tilmicosin (with some exceptions MICs ranged from < or = 0.06 microgram/ml to 1 microgram/ml) and tiamulin (MICs varied from < or = 0.06 microgram/ml to 2 micrograms/ml) were the most effective. Lincomycin, oxytetracycline and enrofloxacin also gave good inhibitions, but with most strains in a higher concentration (MICs ranged in most cases from 2 micrograms/ml to 8 micrograms/ml). The other antibiotics inhibited the growth of O. rhinotracheale only in very high concentrations (colistin) or not at all (apramycin, spectinomycin, polymyxin B). At 37 degrees C, O. rhinotracheale did not survive on egg-shell for more than 24 hours, while upon inoculation into embryonated chicken eggs it killed embryos by the ninth day, and from the 14th day post-inoculation no O. rhinotracheale could be cultured from the eggs at all. These results suggest that O. rhinotracheale is not transmitted via eggs during hatching.     

Effects of probenecid on blood levels and tissue distribution of ampicillin in fowls and turkeys

The effect of probenecid (a benzoic acid derivative which competitively inhibits active secretion of weak organic acids by the renal tubules) on serum ampicillin concentrations and the distribution of ampicillin in body organs was examined in fowls and turkeys. An aqueous solution of probenecid coadministered intramuscularly, at 200 mg/kg, with sodium ampicillin solution, at 25 mg/kg, resulted in peak serum antibiotic concentration of 16.5 microgram/ml. A similar dose of ampicillin administered alone produced a peak level of 4.6 microgram/ml. Subcutaneous injections of sodium ampicillin at 25 mg/kg with aqueous probenecid at 200 mg/kg resulted in a peak serum ampicillin concentration (12.8 microgram/ml) three times as high as the peak produced by the subcutaneous injection of ampicillin alone at 50 mg/kg (4.2 microgram/ml). The elimination half-life (t 1/2) of the drug (30 min) was increased to 1.5 hr by coadministration of probenecid parenterally, and serum antibiotic levels greater than or equal to 5.0 microgram/ml were maintained during 3 hours. Ampicillin seemed to be poorly absorbed from the gastrointestinal tract of fowls. A single oral bolus administration of ampicillin trihydrate aqueous suspension produced a peak of 0.6 microgram/ml, and coadministrations of aqueous probenecid suspension at 20, 50, and 100 mg/kg respectively produced peaks of 0.9, 1.25, and 1.5 microgram/ml. During 4 and 5 days, when ampicillin was added to the drinking water at rates of 200 and 50 mg/liter, serum ampicillin levels were rather low (peaks of 0.20 and 0.12 microgram/ml, respectively), and although these levels were increased by 50% with the coadministration of probenecid they were considered to be of limited clinical value for treating systemic bacterial infections. Probenecid did not change the distribution of ampicillin in the organs.     

A comparison of prophylactic efficacy of tilmicosin and a new formulation of oxytetracycline in feedlot calves

Two replicated-pen field studies were performed under commercial feedlot conditions in western Canada to compare the administration of long-acting oxytetracycline at 30 mg/kg body weight (BW) versus tilmicosin at 10 mg/kg BW to feedlot calves upon arrival at the feedlot. Ten thousand nine hundred and eighty-nine, recently weaned, auction market derived, crossbred beef steer and bull calves were randomly allocated upon arrival at the feedlot to one of 2 experimental groups as follows: oxytetracycline, which received intramuscular long-acting oxytetracycline (300 mg/mL formulation) at a rate of 30 mg/kg BW; or tilmicosin, which received subcutaneous tilmicosin (300 mg/mL formulation) at a rate of 10 mg/kg BW. There were 20 pens in each experimental group. In Study 1 and in the combined analysis, the initial undifferentiated fever (UF) treatment rate was significantly (P < 0.05) higher in the oxytetracycline group as compared with the tilmicosin group. There were no significant (P > or = 0.05) differences in first UF relapse, second UF relapse, third UF relapse, overall chronicity, overall rail, overall mortality, bovine respiratory disease (BRD) mortality, hemophilosis mortality, arthritis mortality, or miscellaneous mortality rates between the experimental groups in either study or in the combined analysis. In addition, there were no significant (P > or = 0.05) differences in initial weight, final weight, weight gain, days on feed, daily dry matter intake, average daily gain, or the dry matter intake to gain ratio between the experimental groups in either study or in the combined analyses. In the economic analysis, there was a net economic advantage of $5.22 CDN per animal in the oxytetracycline group, due to a lower prophylactic cost, even though the UF therapeutic cost was higher.     

Pasteurella anatipestifer infection in turkeys

In a case of excessive mortality in seven-week-old turkeys, the primary lesion at necropsy was severe fibrinous pericarditis and epicarditis. After 48 hours of incubation at 37 C, Pasteurella anatipestifer was isolated. The infection responded to antibiotic therapy with a combination of neomycin and oxytetracycline in the drinking water. The lesions suggested chlamydial infection, but cultural procedures for chlamydia were negative.     

In vivo release of oxytetracycline from a biodegradable controlled-release gel injected subcutaneously in Japanese quail (Coturnix coturnix japonica)

A long-acting, biodegradable, controlled-release formulation of oxytetracycline (CR-OTC) was evaluated in 18 adult Japanese quail (Coturnix coturnix japonica) following a single subcutaneous (s.c.) injection. Prior to characterizing the release of oxytetracycline (OTC) from the CR-OTC, the pharmacokinetic parameters of intravenously (i.v.) administered OTC were determined. Concentrations of free OTC were measured using a bioassay. The plasma concentration-time profile of OTC after a single i.v. injection at 20 mg/kg was best fit to an open two-compartmental model, with the following pharmacokinetic parameters: area under the curve (AUC) = 36.72 mg. h/L, terminal elimination half-life = 2.34 h, clearance (Cl) = 0.545 L/kg/h. Plasma [OTC] was >1.0 micro g/mL for at least 4 h following i.v. injection. The CR-OTC gel was well tolerated at a dosage of 1500 mg/kg s.c. Plasma [OTC] rose to >1.0 micro g/mL within 24 h; it remained >1.0 micro g/mL for at least 10 days in all birds sampled at that time point (n = 9) and for at least 18 days in two of nine birds. Using a deconvolution technique, it was determined that approximately 54.8% of the administered OTC was released from the CR-OTC over the 45-day observation period. This long-acting, biodegradable controlled-release OTC formulation may have potential for the treatment of chlamydophila infections and other OTC-sensitive bacteria in Japanese quail, however further studies are necessary to determine its safety and clinical application.     

A field study of the effects of a monovalent Leptospira borgpetersenii serovar Hardjo strain hardjobovis vaccine administered with oxytetracycline on reproductive performance in beef cattle

OBJECTIVE: To determine whether vaccination with a monovalent Leptospira borgpetersenii serovar Hardjo strain hardjobovis vaccine coupled with parenteral long-acting oxytetracycline treatment would improve the reproductive performance of beef cows. DESIGN: Randomized controlled field trial. ANIMALS: 1,446 Angus-cross beef cows in 8 locations. PROCEDURES: Cows were given 2 doses, 4 weeks apart, of vaccine (treatment; n=741) or placebo (control; 705). Cows in the treatment group were also given a single dose of a long-acting oxytetracycline formulation (20 mg/kg [9.1 mg/lb], SC) at the time of booster vaccination. Estrus synchronization was performed, followed by fixed-time artificial insemination; bulls were introduced 14 days after insemination. Serum and urine samples were obtained on a random subset of cows (n=194) for detection of serologic titers and leptospiruria, and locations were categorized as positive or negative for leptospirosis on the basis of detection of leptospiruric cows. RESULTS: No differences in pregnancy and calving rates between treatment and control groups were detected. Pregnancy rate following artificial insemination was lower among cows in locations positive for leptospirosis than among cows in locations negative for leptospirosis; however, overall pregnancy rate, calving rate following artificial insemination, and overall calving rate did not differ between groups when cows were grouped on the basis of location leptospirosis status. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that under the conditions of the present study, administration of a monovalent Leptospira vaccine in conjunction with systemic administration of oxytetracycline did not significantly improve reproductive performance of beef cows.     

Observations of a long-acting formulation of oxytetracycline in red deer (Cervus elaphus)

Six nine-month-old red deer were injected intramuscularly with a long-acting injectable solution of oxytetracycline (Terramycin-LA, Pfizer Ltd) at a dose rate of 20 mg/kg. Four similar control deer were injected with saline. There was no significant pain response to injection, and only minor palpable swellings at the injection site were observed in three oxytetracycline-treated and one control animal. No statistically significant changes in white blood cell numbers, blood fibrinogen, creatine phosphokinase or glutamic oxaloacetic transaminase concentrations occurred as a result of oxytetracycline administration up to seven days after injection. Mean plasma oxytetracycline concentration reached a peak (4.68 mg/l) two hours after injection and declined to levels below assay sensitivity (0.3 mg/l) in five deer 72 hours after injection, and in all deer by 96 hours after injection. No gross lesions at the injection site were observed at slaughter 30 days after injection. There were traces of oxytetracycline at the injection site muscle of two deer after 30 days, but residues were not detected in injection site muscle from the other four deer, or in any of the liver, kidney or other muscle specimens.     

Eimeria meleagrimitis in young turkeys: effects on weight, blood, and organ parameters

Weight and biochemical studies were conducted on 2-week-old turkeys inoculated with 10(4) to 5 X 10(5) sporulated Eimeria meleagrimitis oocysts, on their pair-fed controls (equivalent food intake), and on control turkeys fed ad libitum. Food consumption and rate of weight gain of all inoculated and pair-fed turkeys fell sharply on day 4 postinoculation (PI), but deaths occurred primarily among the birds inoculated with 5 X 10(5) oocysts. Heart weights (expressed as percentage of body weight) were reduced in inoculated and pair-fed birds, but liver, spleen, and pancreas weights did not differ from those of either control group. Feed conversion (feed consumed/gain) was less efficient for inoculated turkeys than for ad libitum or pair-fed controls and was least efficient for turkeys inoculated with 5 X 10(5) oocysts. Plasma glutamic oxaloacetic transaminase (GOT, aspartate and aminotransferase) activity increased, and carotenoid and total protein levels decreased in inoculated turkeys but not in the pair-fed turkeys, indicating that these changes were caused by the infection and not by reduced food intake. Plasma glutamic pyruvic transaminase (GPT, alanine aminotransferase) remained stable in all groups. Plasma glucose levels of inoculated birds did not differ from those of the control groups, but liver glucose and glycogen levels decreased in both the inoculated and pair-fed birds.     

Long-acting oxytetracycline for control of induced Pasteurella multocida rhinitis in swine

A long-acting oxytetracycline formulation was evaluated for control of rhinitis induced experimentally in pigs with a capsular type A, toxin-negative, low-passage strain of Pasteurella multocida. The pigs were 6 to 7 weeks old and were naturally infected with Haemophilus parasuis. The H parasuis infection was thought to predispose to establishment of P multocida in the nasal cavity. A long-acting oxytetracycline formulation was given IM at the rate of 20 mg/kg, 4 times at 5-day intervals. Medication reduced (P less than 0.05) the severity of turbinate atrophy and the proportion of pigs with P multocida and H parasuis in their nasal cavities. Numbers of colonies of P multocida and H parasuis isolated were also less in medicated pigs.     

The Pharmacokinetics of a Long-acting Oxytetracycline Formulation in Healthy Dogs and in Dogs Infected with Ehrlichia canis

The pharmacokinetic properties of oxytetracycline were studied following a single injection of a long-acting formulation (20 mg/kg body weight) into the semimembranosus muscle of healthy dogs and of dogs that had been experimentally infected with Ehrlichia canis. The disposition curves of the long-acting oxytetracycline formulation before and after infection were best described by a bi-exponential decline after a first-order absorption. The mean maximum serum concentration (C _max) following infection was significantly lower and the time taken to attain this concentration (t _max) was significantly shorter than that in the healthy dogs. The mean apparent elimination half-life (t _1/2) was significantly increased following infection. The corresponding rate constant () was significantly decreased. The absorption half-life (t _1/2ab) was significantly decreased after infection. The volume of distribution at steady state (V _dss) increased significantly following infection. It was concluded that the pharmacokinetic behaviour of a long-acting oxytetracycline in dogs after intramuscular administration is characterized by a two-compartment model with a slow elimination phase. This could be due to flip-flop kinetics. The febrile reaction in experimental E. canis infection affected some pharmacokinetic parameters of oxytetracycline.     

Pharmacokinetics of a long-acting oxytetracycline preparation in ring-necked pheasants, great horned owls, and Amazon parrots

After a single IV or IM dose of a long-acting oxytetracycline (OTC) preparation, serum concentrations were determined at various times in the ring-necked pheasant, great horned owl, and Amazon parrot. Pharmacokinetic parameters, including serum half-life (t1/2) and apparent volume of distribution (Vd) were calculated from the OTC concentration-time curves for each species and route of administration. Significant differences (P less than 0.05) were found in the t1/2 and Vd parameters between species and routes of administration. Dosage regimens to maintain minimum OTC concentration of 5 micrograms/ml of serum were calculated from the t 1/2 and Vd values obtained, using steady-state pharmacokinetics. In the pheasant, the calculated mean IV dose was 23 mg/kg of body weight every 6 hours, whereas the mean IM dose was 43 mg/kg every 24 hours. The mean IM dose was 16 mg/kg every 24 hours for the owl and 58 mg/kg every 24 hours for the parrot. The small volumes required for treatment, the long-dosing interval obtainable, and the broad spectrum of antimicrobial activity of the long-acting OTC preparation studied offered major advantages over other antibiotics commonly used in treating avian species.     

Plasma concentrations of oxytetracycline in swine after administration of the drug intramuscularly and orally in feed

Four pigs were used in a 2 X 2 crossover study to determine plasma oxytetracycline (OTC) concentration and OTC pharmacokinetic variables after IM administration of 2 OTC preparations--long acting OTC and a 100-mg of OTC/ml solution (OTC-LA and OTC-100, respectively)--at a dosage of 20 mg/kg of body weight. In a second study, 3 additional pigs were given ad libitum access to feed containing pure OTC (0.55 g/kg of feed). The mean (+/- SD) peak plasma OTC concentration after OTC-LA administration was 6.0 +/- 2.2 micrograms/ml at 30 minutes; the mean peak plasma OTC concentration after OTC-100 administration was 6.7 +/- 3.4 micrograms/ml at 90 minutes. Mean plasma OTC concentration after oral OTC administration in feed peaked at 0.4 micrograms/ml 48 hours after access to OTC-medicated feed and decreased to 0.25 micrograms/ml by the end of that study. Mean plasma OTC concentration was maintained at greater than 0.5 micrograms/ml for less than 48 hours after OTC-LA administration and for less than 36 hours after OTC-100 administration. Mean plasma OTC concentration decreased to less than 0.2 micrograms/ml by 72 hours after IM administration of either product. Calculation of area under the plasma OTC concentration-time curve (AUC) did not reveal significant difference between the 2 OTC formulations. There also was not significant difference (between OTC-LA and OTC-100) in the value of the disappearance rate constant after administration of either OTC formulation. The data did not indicate significant pharmacologic advantage of OTC-LA, compared with OTC-100, when either formulation was administered IM at a dosage of 20 mg/kg.(ABSTRACT TRUNCATED AT 250 WORDS)     

Absorption of neomycin from the equine uterus: effect of bacterial and chemical endometritis

Plasma concentrations of neomycin were measured after intrauterine infusion of 3.3 mg/kg neomycin sulphate. Mares infected two hours previously with an intra-uterine infusion of beta-haemolytic streptococci absorbed approximately 12 per cent of the neomycin in both the oestrous and the luteal phases of the cycle. Normal mares in oestrus absorbed 6 per cent of the neomycin infused and luteal mares absorbed 56 per cent. In infected mares the peak plasma concentrations occurred two hours after neomycin infusion, earlier than in healthy mares. Cervical flushings after neomycin infusion in infected luteal mares revealed an increased reflux of neomycin when compared with healthy mares. Prior infusion of 30 ml of 10 per cent Lugol's iodine into the uterus resulted in 31 per cent of neomycin being absorbed by oestrous mares and 64 per cent by mares in the luteal phase. Peak plasma concentrations occurred 30 minutes after infusion in both phases. In the luteal phase the mares' absorption of neomycin may have been maximal.