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for use in food-producing animals” is released annually, reporting on the antimicrobial sales data from the prior year and comparisons to previous years. One key finding from the 2021 report was a 19% decline in domestic penicillin sales compared with

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in Journal of the American Veterinary Medical Association

A 15-year-old 3.7-kg (8.1-lb) spayed female domestic shorthair cat was inadvertently administered 0.8 mL (64,864 U/kg [29,484 U/lb]) IV of a common penicillin formulation not intended for IV administration (penicillin G benzathine [150,000 U

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in Journal of the American Veterinary Medical Association

Summary

Plasma concentration of penicillin G was evaluated in beef steers after administration of either a combination of benzathine penicillin G and procaine penicillin G in a 1:1 mixture at a dosage of 9,000 U/kg of body weight, im (n = 5), 24,000 U/kg, im (n = 5), or 8,800 U/kg, sc (n = 5), or benzathine penicillin G alone at a dosage of 12,000 U/kg, im (n = 7). Plasma concentration of penicillin G was measured by use of a high-performance liquid chromatography assay that had a limit of determination of 0.005 µg/ml. At a dosage for this combination of 9,000 U/kg im, and 8,800 U/kg, sc, which are approved label recommendations in Canada, and the United States, respectively, mean (± sem) peak plasma concentration was 0.58 (± 0.15) and 0.44 (± 0.02) µg/ml, respectively. Although plasma penicillin concentration was quantifiable for 7 days in the steers that received 9,000 U/kg, im, and for 4 days in the steers that received 8,800 U/kg, sc, the concentration was < 0.1 µg/ml in both groups after the first 12 hours. After administration of the combination at dosage of 24,000 U/kg, im, there was an initial peak plasma concentration at approximately 2 hours; thereafter, plasma concentration decreased slowly, with half-life of 58 hours. Although plasma penicillin G concentration was quantifiable for 12 days at this dosage, concentration was < 0.1 µg/ml after the first 48 hours. After the initial 48 hours, plasma concentration of penicillin was of similar magnitude and decreased at similar rate for the combination at dosage of 24,000 U/kg and for 12,000 U/kg of benzathine penicillin G alone. Most of the plasma penicillin G concentration in the first 24 hours after administration of a 1:1 combination of benzathine penicillin G and procaine penicillin G is attributable to absorption of procaine penicillin G. After the first 48 hours, most of the plasma drug concentration appeared to be produced by absorption of penicillin G from benzathine penicillin G. Absorption of benzathine penicillin G produces quantifiable plasma penicillin G concentrations for several days, but they are below the level of susceptibility for most bacteria.

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in American Journal of Veterinary Research

Abstract

Objective—To compare the pharmacokinetics of penicillin G and procaine in racehorses following IM administration of penicillin G procaine (PGP) with pharmacokinetics following IM administration of penicillin G potassium and procaine hydrochloride (PH).

Animals—6 healthy adult mares.

Procedure—Horses were treated with PGP (22,000 units of penicillin G/kg of body weight, IM) and with penicillin G potassium (22,000 U/kg, IM) and PH (1.55 mg/kg, IM). A minimum of 3 weeks was allowed to elapse between drug treatments. Plasma and urine penicillin G and procaine concentrations were measured by use of high-pressure liquid chromatography.

Results—Median elimination phase half-lives of penicillin G were 24.7 and 12.9 hours, respectively, after administration of PGP and penicillin G potassium. Plasma penicillin G concentration 24 hours after administration of penicillin G potassium and PH was not significantly different from concentration 24 hours after administration of PGP. Median elimination phase halflife of procaine following administration of PGP (15.6 hours) was significantly longer than value obtained after administration of penicillin G potassium and PH (1 hour).

Conclusions and Clinical Relevance—Results suggest that IM administration of penicillin G potassium will result in plasma penicillin G concentrations for 24 hours after drug administration comparable to those obtained with administration of PGP. Clearance of procaine from plasma following administration of penicillin G potassium and PH was rapid, compared with clearance following administration of PGP. (Am J Vet Res 2000;61:811–815)

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in American Journal of Veterinary Research

Summary

To evaluate the efficacy of penicillin or penicillin and dexamethasone for treatment of infectious bovine keratoconjunctivitis, 6- to 8-month-old beef heifers with clinical signs of infectious bovine keratoconjunctivitis were randomly assigned to 1 of 3 treatment groups: penicillin only, penicillin and dexamethasone, or control. Cattle assigned to the penicillin group (n = 18) were treated with 3 daily subconjunctival injections of procaine penicillin G. Cattle assigned to the penicillin/ dexamethasone group (n = 13) were treated with 3 daily subconjunctival injections of procaine penicillin G and dexamethasone sodium phosphate. Control cattle (n = 14) were not treated. Healing times and frequency of recurrence for corneal ulcers; severity, diameter, and surface area measurements of corneal ulcers; and clinical scores did not differ among the 3 groups. Frequency of Moraxella bovis isolation from specimens of ocular secretions from ulcerated and nonulcerated eyes was similar in all groups. Minimum inhibitory concentration of penicillin G for 95 of the 102 tested M bovis isolates was 0.3 U/ml, and for 7 others was 0.03 U/ml. When first and last specimens from 42 of 45 calves with isolation of M bovis on serial microbial cultures were compared, the susceptibility of each last isolate was similar to that of the corresponding first isolate.

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in Journal of the American Veterinary Medical Association

Penicillin is the antimicrobial for which consultation is most frequently sought through FARAD and is one of the most commonly detected drug residues in tissue and milk. This article reviews studies related to extralabel penicillin administration

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine tissue depletion of penicillin G in calves after oral ingestion with milk replacer and estimate a withdrawal period.

Design—Longitudinal controlled trial.

Animals—26 Holstein calves.

Procedure—Once daily, 24 calves were fed milk replacer containing procaine penicillin G (0.68 mg/kg [0.31 mg/lb] of body weight); 2 calves served as controls. After 1 feeding, 12 calves were euthanatized in groups of 3 each 4, 6.5, 9.5, and 13 hours after feeding. After 14 days, 12 calves were euthanatized in groups of 3 each 4, 6.5, 9.5, and 13 hours after the final feeding. Concentrations of penicillin G were determined in tissues, blood, and urine by use of high-performance liquid chromatography.

Results—Penicillin G was not detected in muscle samples of treated calves. The highest concentrations of penicillin G in plasma, kidney, and liver were 13 ng/ml, 92 ng/g, and 142 ng/g, respectively. Thirteen carcasses had violative drug residues; 12 had violative residues in the liver only, and 1 had violative residues in the liver and kidney. A 21-hour withdrawal period was estimated.

Conclusions and Clinical Relevance—Liver had the highest concentration of penicillin G and was most likely to have violative residues. Feeding calves milk containing penicillin G has the potential to cause violative drug residues in tissues. It is recommended to observe an appropriate withdrawal time prior to slaughter if calves are fed milk from cows treated with penicillin G. (J Am Vet Med Assoc 2001;219: 346–350)

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine whether, and at what time, penicillin enters milk at a concentration that is detectable following bulbar subconjunctival injection in lactating dairy cows.

Design—Randomized clinical trial.

Animals—66 Holstein cows that were at least 2 weeks past calving and had not been treated with antibiotics in the preceding 30 days.

Procedure—Cows were randomly assigned to receive a treatment of 1 ml (300,000 units) procaine penicillin G by bulbar subconjunctival injection or remain untreated. Composite milk samples were collected immediately before treatment and 4, 10, 16, 22, 28, and 40 hours after treatment. Milk samples were tested by use of a commercial test for β-lactam antibiotics.

Results—Among penicillin-treated cows, the first positive test results were observed 4 hours after treatment, and the last positive result was observed 22 hours after treatment. The percentages of positive test results before treatment and at 4, 10, 16, 22, 28, and 40 hours after treatment were 0, 9, 87, 42, 8, 0, and 0%, respectively. None of the untreated cows had positive test results for β-lactam antibiotics at any sampling time.

Conclusions and Clinical Relevance—Penicillin was detected in milk for up to 22 hours after a single subconjunctival injection of procaine penicillin G in cows. This result should be considered when recommending milk withholding periods following the administration of penicillin by this route in lactating dairy cows. (J Am Vet Med Assoc 2000;217:369–371)

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in Journal of the American Veterinary Medical Association

SUMMARY

Using 7 penicillins (amoxicillin, ampicillin, methicillin, penicillin G, oxacillin, cloxadllin, and dicloxadllin), simultaneous and direct determination of residual penicillins in biological samples was carried out by use of bioassay and high-performance liquid chromatography with spectrophotometric or fluorometric detectors.

By use of assay medium seeded with penicillin-sensitive Micrococcus luteus (ATCC No. 9341) as a test organism, we were able to detect penicillins even at low concentrations. All penicillins treated with 10 U of penicillinase/ml did not produce inhibition zones by disk testing even at a concentration of 100 μg of penicillin/ml/assay plate.

Using a mobile phase of acetonitrile:methanol: 0.01M KH2PO4 (19:11:70, v/v/v; pH, 7.1), standard solutions of the penicillins were separated from each other by use of high-performance liquid chromatography analysis, producing symmetric peaks without tailing each of which had a characteristic retention time. Simultaneous detection of residual penicillins in bovine serum, kidneys, and liver, for the 5 penicillins for which analysis was possible by use of the uv method, yielded recovery rates from 71.4 to 102.3%; for the 2 amino-penicillins, amoxicillin and ampicillin, which could only be detected by use of the fluorometric method, recovery rate ranged from 72.9 to 103%.

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in American Journal of Veterinary Research

intervals (WDIs) following ELDU from the Food Animal Residue Avoidance and Depletion Program (FARAD). Penicillin is one of the most commonly used medications to treat disease in food-producing animals across the globe. 1 , 2 However, it was approved over 40

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in Journal of the American Veterinary Medical Association