Pharmacokinetics of levofloxacin following oral administration of a generic levofloxacin tablet and intravenous administration to dogs

Bernard S, Blackie K, Gronlund U, Battersby I. Evaluation of antimicrobial purchasing by companion animal veterinary facilities in Canada, the United Kingdom, and the United States of America (2019-2021)

BACKGROUND

Measuring antimicrobial use is a core component of antimicrobial stewardship. Purchasing data may be easier to obtain than prescription data in some situations, but differences in clinic size, caseload and collection timeframes must be considered.

OBJECTIVE

Our objective was to evaluate purchases of systemic antibacterial agents by small animal veterinary facilities in 5 networks across 3 countries, using a mg/veterinarian full time equivalent (FTE)/week as the metric.

METHODS

Data were obtained from purchasing records of 2194 veterinary facilities from networks from the United States (US, n = 3: US-A, 1036 facilities; US-B, 101 facilities; US-C, 886 facilities), Canada (n = 1: 117 facilities) and the United Kingdom (UK, n = 1: 54 facilities) during 2019-2021.

RESULTS

In total, 20 020 269 767 mg (20.02 t) of antimicrobials were purchased. Overall differences between the UK and North America were driven by significantly higher purchases of amoxicillin-clavulanic acid in the UK (P < .001), with substantially less purchasing of third generation cephalosporins in the UK (P < .0001). A significant association was found between FTE and purchasing, with decreased purchasing (mg/FTE/week) as facility FTE increased. Significant differences also were found among US regions. Facilities in the top 10% of total purchasing accounted for 23%-30% of purchases, compared to only 1.6%-3.8% for the bottom 10%.

CONCLUSIONS AND CLINICAL IMPORTANCE

These data provide useful information about general purchasing trends, inter- and intraregional differences and differences among facility types and identify high purchasing outliers for further investigation.

In vitro and ex vivo antibacterial activity of levofloxacin against Pasteurella multocida and Escherichia coli isolated from rabbits (Oryctolagus cuniculus) - A preliminary study

Levofloxacin veterinary formulations are available in Argentina, China and India for the use in dogs, cattle, pig and sheep, but not currently in the rabbit. Only the extra-label use in rabbits is possible. Levofloxacin is not labelled for veterinary use in the EU or the USA. The activity of levofloxacin against rabbit pathogens Pasteurella multocida (P. multocida) and Escherichia coli (E. coli) was evaluated. Minimum inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) were determined in broth and serum for 10 P. multocida isolates and 5 E. coli isolates from rabbits. One isolate of each bacterial species was used for the time-killing curve study in vitro and ex vivo. In vitro AUC24 /MIC ratios were used for building the inhibitory pharmacodynamic Imax model. The P. multocida MIC were 0.008-0.5 μg/mL, MBC - 0.015-0.5 μg/mL. Escherichia coli MIC was 0.008-0.03 μg/mL and MBC - 0.03-0.25 μg/mL. Bacterial counts were reduced to the limit of detection after 24 h with levofloxacin concentrations of 2 MIC and higher. All serum samples from rabbits treated with levofloxacin eliminated the bacteria within 24 h. AUC24 /MIC ratios for bacteriostatic, bactericidal and bacterial elimination effects for P. multocida and E. coli isolates were 21, 29 and 75 h and 27, 32 and 60 h, respectively. Proposed daily doses against P. multocida (MIC = 0.015 μg/mL) and E. coli (MIC = 0.03 μg/mL) isolates were calculated as ≤0.91 and ≤1.43 mg/kg, respectively. Fluoroquinolones are categorized by WHO as 'highest priority critically important antimicrobials'. Considering the increasing importance of antimicrobial stewardship, antimicrobials from a lower importance category that are active against the isolate of interest should be used in preference to fluoroquinolones. Fluoroquinolone use in veterinary medicine should be based on antimicrobial susceptibility testing in order to mitigate the risk to public health and prevent the spread of bacterial resistance.

PHARMACOKINETICS OF RECTALLY AND ORALLY ADMINISTERED LEVOFLOXACIN IN ASIAN ELEPHANTS (ELEPHAS MAXIMUS)

Appropriate and effective antibiotic use is a critical component of veterinary medicine, but there are variations across species regarding dosage and administration of these drugs. Oral or rectal routes of administration are typically used in elephants, but not all medications can achieve adequate concentrations rectally. The fluoroquinolone antimicrobials are used in elephants because of their favorable antimicrobial spectrum and pharmacokinetics compared with other oral agents. They are commonly used as part of multiple antibiotic regimens for the treatment of tuberculosis (Mycobacterium tuberculosis). The objective of this study was to determine the pharmacokinetic profile of levofloxacin after oral and rectal administration in Asian elephants (Elephas maximus). Dosages of 5 mg/kg orally and 15 mg/kg rectally were evaluated in 13 Asian elephants. Blood was collected at various time points from 0 to 72 h for pharmacokinetic analysis. Pharmacokinetic parameters were determined and reached concentrations above minimum inhibitory concentrations of various bacterial organisms via both routes. A pharmacokinetic-pharmacodynamic assessment was used to estimate appropriate minimal inhibitory concentrations for bacteria that could be potentially treated with this antimicrobial. Based on these findings, levofloxacin may be a consideration for administration orally (5 mg/kg) and rectally (15 mg/kg) in Asian elephants. Antimicrobial stewardship principles, culture and susceptibility of suspected pathogens, and blood level monitoring should be used to tailor administration of levofloxacin in this species.

Levofloxacin in veterinary medicine: a literature review

A potent third-generation antimicrobial fluoroquinolone drug, levofloxacin was introduced into human clinical practice in 1993. Levofloxacin is also used in veterinary medicine, however its use is limited: it is completely banned for veterinary use in the EU, and used extralabel in only companion animals in the USA. Since its introduction to clinical practice, many studies have been published on levofloxacin in animal species, including pharmacokinetic studies, tissue drug depletion, efficacy, and animal microbial isolate susceptibility to levofloxacin. This literature overview highlights the most clinically relevant and scientifically important levofloxacin studies linked to the field of veterinary medicine.

Pharmacokinetics of levofloxacin mesylate in healthy adult giant panda after single-dose administration via different routes

The pharmacokinetics of levofloxacin mesylate in healthy adult giant panda is unknown. In this study, the pharmacokinetics of levofloxacin after intramuscular administration at a dose of 2 mg/kg and oral administration at a dose of 3 mg/kg in healthy adult giant pandas was determined. Levofloxacin concentrations in plasma were determined using liquid chromatography. In the levofloxacin intramuscular administration group, the absorption and elimination half-lives of the drug were determined to be 0.123 (range: 0.02) hr and 5.402 (range: 0.70) hr, respectively. In the levofloxacin oral administration group, the absorption and elimination half-lives were determined to be 0.325 (range: 0.02) hr and 7.143 (range: 0.63) hr, respectively. Furthermore, the blood-drug concentration of levofloxacin was found to be above 1 μg/ml after 8 hr of intramuscular administration and above 0.5 μg/ml after 12 hr of oral administration. In this study, HPLC conditions and pretreatment methods of plasma samples were optimized and a detection method was established. Our results indicated that in healthy adult giant pandas, levofloxacin was rapidly absorbed and slowly eliminated. This study will therefore provide to be a guide in veterinary research and will be helpful in the rational use of levofloxacin in giant panda.

Levofloxacin pharmacokinetics and tissue residue concentrations after oral administration in Bilgorajska geese

1. The aim of this study was to assess the pharmacokinetics of levofloxacin, a third-generation fluoro-quinolone antimicrobial drug, in geese (n = 26) after either single intravenous or oral administration, and to evaluate the depletion profile in goose muscle, heart, liver, kidney and lung after a single oral dose.2. The pharmacokinetic study involved 16 geese which were randomly divided into two groups (n = 8/group), the first received levofloxacin (2 mg/kg) intravenously while the second was treated with orally (5 mg/kg). The tissue depletion study involved 10 geese which were dosed orally (5 mg/kg) and two animals were killed at different time-points in order to collect the selected tissues. Levofloxacin was quantified in all the matrices tested by a validated high-performance liquid chromatography (HPLC) method, using a spectrofluorimetric detector. The pharmacokinetics were analysed using a non-compartmental model.3. Plasma concentrations were quantified after up to 24 h in animals administered intravenously and up to 48 h after oral treatment. Levofloxacin was rapidly absorbed after oral administration (T_max = 0.38 h) showing high bioavailability (95.57 ± 20.61%). The drug showed a moderate volume of distribution (1.40 ± 0.28 ml/g) and rapid clearance (0.28 ± 0.06 ml/g/h). No statistical differences in estimates were found between the two different administration methods (P > 0.05). Drug residues were highest at 6 h and decreased constantly up to 48 h in all the selected tissues. Liver and kidney had the highest levofloxacin concentrations.4. According to the pharmacokinetic/pharmacodynamic surrogate index (AUC/MIC) the levofloxacin dose regimen (after oral administration) used in the present study could be active against bacteria at a minimum inhibitory concentration (MIC) > 0.24  μg/ml in geese. In addition, drug accumulation in the liver might be controlled using an estimated preliminary withdrawal time of 90 h.

Antimicrobial agent use in small animals what are the prescribing practices, use of PK-PD principles, and extralabel use in the United States?

In this review, the availability and deficiencies of current antimicrobial agents for companion animals in the United States are described. Although several active agents are FDA-approved for small animals, there are many unmet needs. These needs are greatest for cats, for the treatment of antibiotic drug-resistant infections, and to treat new or emerging pathogens that were not considered on older labels. The older agents approved before 1997 are often outdated, unavailable, or have inaccurate labeling. Subsequently, veterinarians treat dogs and cats with many unapproved antimicrobial agents that are licensed for human use. Although these drugs may be effective, there are also concerns that this use can produce drug-resistant bacteria that may be a public health risk. Although this concern is real, there is also evidence that any antimicrobial use in small animals can produce resistant fecal bacteria and stewardship principles should aim at reducing any unnecessary antibiotic use. This could be accomplished by avoiding some of the older, ineffective, or outdated agents described in this paper. There is a need for incentives to approve new agents that will be more appropriate for treating infections in companion animals without increasing the risk of drug-resistant bacteria that could potentially be transferred to humans and the environment and create a public health risk.

Pharmacokinetic profiles of levofloxacin after intravenous, intramuscular and subcutaneous administration to rabbits (Oryctolagus cuniculus)

Levofloxacin pharmacokinetic profiles were evaluated in 6 healthy female rabbits after intravenous (I/V), intramuscular (I/M), or subcutaneous (S/C) administration routes at a single dose of 5 mg/kg in a 3 × 3 cross-over study. Plasma levofloxacin concentrations were detected using a validated Ultra Performance Liquid Chromatography method with a fluorescence detector. Levofloxacin was quantifiable up to 10 h post-drug administration. Mean AUC0-last values of 9.03 ± 2.66, 9.07 ± 1.80, and 9.28 ± 1.56 mg/h*L were obtained via I/V, I/M, and S/C, respectively. Plasma clearance was 0.6 mL/g*h after I/V administration. Peak plasma concentrations using the I/M and S/C routes were 3.33 ± 0.39 and 2.91 ± 0.56 μg/mL. Bioavailability values, after extravascular administration were complete, - 105% ± 27% (I/M) and 118% ± 40% (S/C). Average extraction ratio of levofloxacin after I/V administration was 7%. Additionally, levofloxacin administration effects on tear production and osmolarity were evaluated. Tear osmolarity decreased within 48 h post-drug administration. All 3 levofloxacin administration routes produced similar pharmacokinetic profiles. The studied dose is unlikely to be effective in rabbits; however, it was calculated that a daily dose of 29 mg/kg appears effective for I/V administration for pathogens with MIC < 0.5 μg/mL.