Distribution and binding kinetics of ciprofloxacin and ofloxacin in the hindlimb of the rat

Design optimality for models defined by a system of ordinary differential equations

Many scientific processes, specially in pharmacokinetics (PK) and pharmacodynamics (PD) studies, are defined by a system of ordinary differential equations (ODE). If there are unknown parameters that need to be estimated, the optimal experimental design approach offers quality estimators for the different objectives of the practitioners. When computing optimal designs the standard procedure uses the linearization of the analytical expression of the ODE solution, which is not feasible when this analytical form does not exist. In this work some methods to solve this problem are described and discussed. Optimal designs for two well-known example models, Iodine and Michaelis-Menten, have been computed using the proposed methods. A thorough study has been done for a specific two-parameter PK model, the biokinetic model of ciprofloxacin and ofloxacin, computing the best designs for different optimality criteria and numbers of points. The designs have been compared according to their efficiency, and the goodness of the designs for the estimation of each parameter has been checked. Although the objectives of the paper are focused on the optimal design field, the methodology can be used as well for a sensitivity analysis of ordinary differential equation systems.

Carboxymethyl cellulose (CMC) based semi-IPNs as carriers for controlled release of ciprofloxacine: an in-vitro dynamic study

Semi-interpenetrating polymer networks (IPNs) of carboxymethyl cellulose (CMC) and polyacrylic acid were prepared and its potential for controlled release of ciprofloxacine (Cfx) was assessed. The IPNs were characterized by IR spectral analysis and Environmental scanning electron microscopy (ESEM). The entrapped drug was examined for its antibacterial activity and chemical stability. The effects of experimental parameters such as varying chemical composition of the IPNs, percent loading of Cfx, pH and temperature of release medium and presence of salt ions in outer solution were examined on the release profile of the drug. On the basis of Fick's power law equations, the diffusion exponents (n) and diffusion constant (D) were evaluated for different IPNs compositions. From the kinetic parameter data, an attempt was made to resolve the mechanism of the release process of Cfx.

Characterization of crosslinked high amylose starch matrix implants. 2. In vivo release of ciprofloxacin

The purpose of this study was to develop a crosslinked high amylose starch (CLHAS) matrix implant as a sustained antimicrobial delivery system for local prevention and/or treatment of osteomyelitis. Implants (200 mg) of CLHAS containing 2.5% (5 mg), 7.5% (15 mg), 15.0% (30 mg) and 20.0% (40 mg) of ciprofloxacin (CFX), were prepared by direct compression of dry blends. Rabbits were administered six 2.5, two 7.5, one 15.0 or one 20.0%-CFX implants along the femur between the quadriceps and biceps femoris muscles to determine systemic (serum) versus local (muscle and bone) CFX concentrations over 1 month. Blood samples were taken throughout the study for CFX assay. Muscle and femur were collected at 3, 7, 14, 21 and 28 days after implantation for host response evaluation and CFX assay. Residual polymer was explanted to determine the remaining dose of CFX. All animals remained healthy during the study. Local tissue reaction was mild and limited to the implantation site. Serum CFX concentrations remained low regardless of implant loading. Increased drug loading resulted in a higher and longer release of CFX in muscle and in bone. Local CFX concentrations were detected largely in excess of the MIC over 28 days with 20.0%-CFX implants. More residual CFX in polymer was detected over a longer period of time at high loading. These results strongly support the development of CLHAS implants for local antibacterial therapy.

Characterization of crosslinked high amylose starch matrix implants. 1. In vitro release of ciprofloxacin

The objective of this study was to characterize in vitro the potential of crosslinked high amylose starch (CLHAS) as an implant matrix for the delivery of ciprofloxacin (CFX). Direct compression of dry blends of four different matrices: control CLHAS; CLHAS with 1% hydrogenated vegetable oil (HVO); and CLHAS with 10 or 20% hydroxypropylmethylcellulose (HPMC), each of them with three CFX loadings (2.5, 5.0 and 7.5%) was performed to prepare twelve implant formulations. All CLHAS implants were used for 24-h dissolution tests to evaluate swelling, erosion, water uptake and CFX release. Additionally, 1%-HVO- CLHAS implants were used for an extended dissolution test. The presence of HPMC in the matrix increased CFX release rate, swelling, erosion and water uptake in a concentration-dependent manner whereas HVO had no effect. With increasing drug loading, a decrease of cumulative CFX percent release was observed in both 24-h and extended dissolution tests. Of the different formulations tested, CLHAS implants with 1% HVO and 7.5% CFX provided the longest period of drug delivery without any initial burst effect.

Determination of tissue spaces of the isolated hindlimb of the rat using netilmicin as an extracellular space indicator

The kinetic behaviour of drugs in extracellular space is of interest as it influences the drug's access to, and permanence in, those areas of the body upon which drugs exert pharmacological or toxicological actions. A series of experiments was carried out to characterize the vascular, interstitial and cellular spaces of the isolated hindlimb of the rat. Certain specific experimental conditions were met: body weight was under 230 g to avoid fat tissue in the preparations; a perfusion flow rate of 3 mL min(-1); and 3% of bovine albumin in the perfusate supplied at 25 degrees C to the tissues. The isolation of the hindlimb followed the method described by Ruderman with some modifications to restrict the perfusion to the right hindlimb. Tritiated water, netilmicin and methylene blue were injected separately and efferent fluid samples were collected for 15 min after solute injection. Analysis of the efferent curves was performed to calculate the statistical moments (AUC, area under concentration-time curve; MTT, mean transit time; VTT, variance of mean transit times) and solute distribution volumes, which were subsequently used to estimate the tissue spaces of the isolated hindlimb. The results revealed that methyl blue and netilmicin can be respectively used as alternatives to radiolabelled indicators of the vascular and extracellular spaces of tissues included in the rat isolated hindlimb.

Influence of dose on the distribution kinetics of ciprofloxacin and ofloxacin in the isolated hindlimb of the rat

The aim of this study was to determine whether the dose influences the distribution kinetics of ciprofloxacin and ofloxacin in muscle- bone- and skin-tissues included in the isolated hindlimb of the rat. Experiments were carried out in the isolated perfused hindlimb of the rat, administering a single dose of 45, 450 or 900 microg of each quinolone as a bolus injection. Outflow perfusate samples were collected for 20 min and drug levels were determined by an HPLC technique. The mean transit time (MTT) and the distribution volume of ciprofloxacin significantly increased with the dose injected (MTT=1.47+/-0.69, 8.74+/-0.27 and 9.52+/-2.95 min for 45, 450 and 900 microg, respectively). A similar situation was observed with ofloxacin, although the increase in these parameters was less pronounced (MTT=3.65+/-0.86, 7.92+/-2.03 and 8.32+/-1.70 min for 45, 450 and 900 microg, respectively). The distribution of ciprofloxacin and ofloxacin in the rat hindlimb appears to be a dose-dependent process, at least for the dose range considered in this study. This might explain the high variability in the distribution coefficients reported for these drugs in literature.