In vitro and in vivo evaluation of levofloxacin sustained-release capsules

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

OBJECTIVE

To determine the pharmacokinetics of levofloxacin following oral administration of a generic levofloxacin tablet and IV administration to dogs and whether the achieved plasma levofloxacin concentration would be sufficient to treat susceptible bacterial infections.

ANIMALS

6 healthy adult Beagles.

PROCEDURES

Levofloxacin was administered orally as a generic 250-mg tablet (mean dose, 23.7 mg/kg) or IV as a solution (15 mg/kg) to each dog in a crossover study design, with treatments separated by a minimum 2-day washout period. Blood samples were collected at various points for measurement of plasma levofloxacin concentration via high-pressure liquid chromatography. Pharmacokinetic analysis was performed with compartmental modeling.

RESULTS

After oral administration of the levofloxacin tablet, mean (coefficient of variation) peak plasma concentration was 15.5 μg/mL (23.8%), mean elimination half-life was 5.84 hours (20.0%), and mean bioavailability was 104% (29.0%). After IV administration, mean elimination half-life (coefficient of variation) was 6.23 hours (14.7%), systemic clearance was 145.0 mL/kg/h (22.2%), and volume of distribution was 1.19 L/kg (17.1%).

CONCLUSIONS AND CLINICAL RELEVANCE

In these dogs, levofloxacin was well absorbed when administered orally, and a dose of approximately 25 mg/kg was sufficient to reach pharmacokinetic-pharmacodynamic targets for treating infections with susceptible Enterobacteriaceae (ie, ≤ 0.5 μg/mL) or Pseudomonas aeruginosa (ie, ≤ 1 μg/mL) according to clinical breakpoints established by the Clinical and Laboratory Standards Institute.

Multivariate analysis as a method to understand variability in a complex excipient, and its contribution to formulation performance

A key part of the Risk Assessment of excipients is to understand how raw material variability could (or does) contribute to differences in performance of the drug product. Here we demonstrate an approach which achieves the necessary understanding for a complex, functional, excipient. Multivariate analysis (MVA) of the certificates of analysis of an ethylcellulose aqueous dispersion (Surelease) formulation revealed low overall variability of the properties of the systems. Review of the scores plot to highlight batches manufactured using the same ethylcellulose raw material in the formulation, indicated that these batches tend to be more closely related than other randomly selected batches. This variability could result in potential differences in the quality of drug product lots made from these batches. Manufacture of a model drug product from Surelease batches coated using different lots of starting material revealed small differences in the release of a model drug, which could be detected by certain model dependent dissolution modeling techniques, but they were not observed when using model-independent techniques. This illustrates that the techniques are suitable for detecting and understanding excipient variability, but that, in this case, the product was still robust.

Discriminatory dissolution method for quality control measurements of carbamazepine immediate release tablets based on in vitro--in vivo investigations

The purpose of this study was to identify a discriminatory dissolution method able to predict the in vivo performance of tablet formulations designed for carbamazepine (CBZ). After evaluation of dissolution medium and rotation speed using a 2⁵ central composite design and investigation of the in vivo release behaviors in beagle dogs, the dissolution method of CBZ 100 mg tablets was validated using a USP apparatus II, at a rotation speed of 75 rpm, and 900 ml deaerated water with 0.5% sodium lauryl sulfate (w/v) as the dissolution medium. Dissolution profiles were evaluated by the Weibull parameters and the modified fit factor, ƒ^(1,area). The in vitro-in vivo relationship of CBZ tablets was examined. Compared with the results from the USP and Chinese Pharmacopoeia monograph, the proposed system provides a superior discriminatory method. Since the dissolution method in pharmacopoeia for CBZ tablets is unable to distinguish between a good and a bad product, the method presented here can be used for the quality control testing of CBZ tablets.