Preparation and physicochemical characterization of amoxicillin beta-cyclodextrin complexes

Amoxicillin (AMOX), a penicillin A, belongs to the beta-lactam family It is usually the drug of choice within the class because it is better absorbed, following oral administration, than other beta-lactam antibiotics. Its beta-lactamase degradation might be prevented by using a molecular [AMOX:beta-CD] complex. The aim of this work was to prepare complexes using two methods and then characterize interactions between AMOX and the native beta-CD. The extent of complexation in solution has been evaluated by high-performance liquid chromatography (HPLC), nuclear magnetic resonance (NMR), and 2D rotating-frame Overhauser enhancement spectroscopy (2D ROESY). Mass changes (TG), calorimetric effects (DSC), and mass spectrometry (MS) were determined on the same sample under identical conditions using the Skimmer coupling system. Skimmer and infrared spectroscopy (FT-IR) were used to characterize the solid state of the binary system. Complexation of AMOX with beta-CD was proven by FT-IR, NMR, DSC, and HPLC. The 2D ROESY spectra did not show any dipolar proton interaction of the AMOX with cyclodextrin. The 1:1 stoichiometry of the complex was obtained by HPLC. The stability constant for AMOX with beta-CD was determined to be 1,878 M(-1). In the [AMOX:beta-CD] complex, the phenyl group is included inside the beta-CD, and the ionized carboxyl group on the penam ring forms hydrogen bonds with the secondary hydroxyl groups of another beta-CD to keep the complex stable. Preparation methods allowed exactly the same complex.

[What future for ribavirin beyond hepatitis C therapy?]

Most of emerging and re-emerging diseases are due to RNA viruses and available drugs are insufficient. Currently the ribavirin is only licensed for the treatment of chronic hepatitis C infection, whereas this guanosin analogue has a broad-spectrum in vitro activity against many DNA and RNA viruses. It was consequently used as a last resort, in emergency state like avian influenza or in front of new viruses (SARS). The strategies for development of new antiviral drugs are usually based on virus structure and properties. In regard to recent development of chemical vector designed for improving drug bioavailability, use of former drug, like ribavirin, could be reconsidered. For example, complexation of ribavirin with cyclodextrins, cyclic oligosaccharide vectors, can improve its bioavailability in central nervous system and improve encephalitis treatment.

Evaluation by Q-RTPCR of the efficacy of ribavirin complexed with beta-cyclodextrin against measles virus in a mouse encephalitis model

The objective of this work was to study the antiviral activity of ribavirin on measles encephalitis infection when using cyclodextrins as carriers. The use of cyclic oligosaccharides can promote the activity of many drugs and the benefit of the association of ribavirin with beta-cyclodextrin has already been demonstrated in vitro. Intracranial inoculation of the rodent adapted neurovirulent CAM/RB strain of measles virus induces encephalitis in CBA/ca mice. The antiviral activity of the complex ribavirin/beta-cyclodextrin at molar ratio 1:1 has been evaluated in vivo in the above encephalitis model. CBA/ca mice were treated with daily intraperitoneal injection of ribavirin (40 mg/kg) with or without beta-cyclodextrin. The viral load in the brain of mice was quantified by real-time Reverse transcription-Polymerase chain reaction. Treatment of mice by the complex ribavirin/beta-cyclodextrin (1:1) by intraperitoneal route decreases the viral load in the brain of 1.1 and 0.7 log(10) Eq copies x mL(-1) compared to distillated water and ribavirin treatment, respectively. At the same time, free ribavirin injection shows a negligible difference compared to treatment by distillated water.

Improved antiviral activity in vitro of ribavirin against measles virus after complexation with cyclodextrins

Despite vaccination, measles remains a burden in both developed and developing countries and complications may necessitate an efficient therapy. Measles virus (MEV) is susceptible to ribavirin (RBV), but the use of this drug is limited by its toxicity. Cyclodextrins (CDs) can form complexes with numerous molecules, improving their bioavailability and their biological properties. We have evaluated in vitro the antiviral effects of complexes of RBV with alpha-, beta- or gamma-CD against two clade A laboratory strains of MEV (Edmonston and CAM/RB) grown on Vero cells. Complexation of RBV with alpha-CD or beta-CD lead to a five-fold or a two-fold decrease in the 50% inhibitory concentration, respectively, against both MEV strains. In contrast, gamma-CD complexation showed no modification.

Evaluation of peroral silicone dosage forms in humans by gamma-scintigraphy

Gastric emptying of oral silicone dosage forms was studied in humans by gamma-scintigraphy. To achieve a constant and predictable residence time in the stomach, three different formulations based on known concepts such as controlled swelling were investigated. The importance of physical parameters such as size or shape were also examined to assess the feasibility of designing a dosage form for gastric retention. Three shapes: minimatrices, extruded rods and moulded slabs were screened. To label the silicone polymer, two isotopes, used routinely in nuclear medicine departments, were selected: iodine-123 and indium-111. To select the most suitable isotope, the yield and the stability of the labelling were determined in vitro on the pharmaceutical dosage forms. The residence time of these silicone formulations, labelled with iodine and administered in hard gelatine capsules, was monitored in 12 subjects with a gamma camera. The study was performed under fed conditions after ingestion of a standardised meal labelled with indium. The minimatrices provided at least 3 h retention, slabs exhibited 4 h 40 min retention. For the rods the mean residence time in the stomach was around 4 h 20 min. In addition, a correlation was established between the gastric emptying of rods and the half-gastric residence time of meal. On the contrary, such a correlation was not observed for the slabs.

Effect of the formulation on the in-vitro release of propranolol from gellan beads

Gellan gum beads of propranolol hydrochloride, a hydrophilic model drug, were prepared by solubilising the drug in a dispersion of gellan gum and then dropping the dispersion into calcium chloride solution. The droplets formed gelled beads instantaneously by ionotropic gelation. Major formulation and process variables which might influence the preparation of the beads and the drug release from gellan gum beads were studied. Very high entrapment efficiencies were obtained (92%) after modifying the pH of both the gellan gum dispersion and the calcium chloride solution. The beads could be stored for 3 weeks in a wet or dried state without modification of the drug release. Oven-dried beads released the drug somewhat more slowly than the wet or freeze-dried beads. The drug release from oven-dried beads was slightly affected by the pH of the dissolution medium. Gellan gum could be a useful carrier for the encapsulation of fragile drugs and provides new opportunities in the field of bioencapsulation.

Influence of different physicochemical conditions on the release of indium oxine from nanocapsules

The main purpose of this study was to determine the influence of factors (pH, enzymes, etc.) chosen partially to mimic in vivo conditions on the release of a model drug, indium oxine, from polyepsiloncaprolactone (PCL) nanocapsules in vitro. A nanocapsule suspension, an emulsion (O/W), and a solution in olive oil were prepared in order to compare the release of a radioactive tracer, indium oxine, as a function of time by an in vitro dialysis method. Nanocapsules were prepared by interfacial deposition of PCL and characterized by particle size distribution (laser light scattering) and determination of the polymer molecular weight by gel permeation chromatography (GPC). The results of this study suggest that the partition coefficient between the acceptor medium and the olive oil is the major parameter governing the release of the isotope, at least in the absence of significant enzyme activity. The PCL wall of nanocapsules is a barrier that does not seem to retard the release of indium. The addition of porcine liver esterases accelerated the degradation of PCL. This study confirms that the release of a drug from nanocapsules may be very different depending on the in vivo location, that is, the administration site.

Preparation of silicone microspheres by emulsion polymerization: application to the encapsulation of a hydrophilic drug

The objective of this work was to evaluate the ability of appropriate silicone elastomers to encapsulate hydrophilic compounds in microspheres prepared according to a multiphase emulsion-polymerization process. The particle size of the microspheres can be modified by controlling the usual emulsification parameters, such as the viscosity of the different phases, shear rates and surface activity properties of additives. The encapsulation efficiencies of a hydrophilic drug, propranolol hydrochloride, were very high but its release rates were very slow. Osmotic agents such as glycerol and propylene glycol did not enhance the release rate, whereas it was slightly increased by both sodium chloride addition and higher drug loading.

Stability study of nanoparticles of poly(epsilon-caprolactone), poly(D,L-lactide) and poly(D,L-lactide-co-glycolide)

The objective was to evaluate the stability of nanoparticles prepared with poly(epsilon-caprolactone), poly(D,L-lactide) and poly(D,L-lactide-co-glycolide) polymers and stored at different temperatures and in different media. The stability parameters studied were molecular weight and crystallinity of the polymer, nanoparticle size and pH. The results show that the stability of polymeric nanoparticles depends on (i) the type of polymers with the following increasing order of polymer stability: PLA25GA50 < PLA37.5GA25 < PLA50 = PCL, (ii) the storage temperature: PCL and PLA50 nanoparticles can be kept at 4 degrees C and RT during one year, while PLA37.5GA25 and PLA25GA50 nanoparticles have to be stored at 4 degrees C, and (iii) the storage conditions: buffering or freeze-drying nanoparticles improves stability.

Preparation and characterization of ethylcellulose microspheres containing 5-fluorouracil

Ethylcellulose microspheres containing 5-fluorouracil (5-FU) were prepared by a solvent evaporation technique using light mineral oil as the continuous phase. The drug was suspended in the acetone solution of the polymer. Three drug/polymer ratios (1/1, 1/2 and 1/3) were utilized. The microspheres were studied with respect to size, drug content and surface characteristics; the higher the polymer content, the smoother the microspheres. The drug was suspended in the polymer and the drug loading was important (more than 90%) with the three types of microspheres. In vitro dissolution studies in phosphate buffer showed that the 5-FU release was dependent on the drug/polymer ratio for the 400-500 microns granulometric fraction.

Stability of parenteral ceftriaxone disodium solutions in frozen and liquid states: effect of freezing and microwave thawing

The stability of ceftriaxone disodium solutions stored in glass bottles was tested in two parenteral solvents (0.9% NaCl; 5% dextrose) at two concentration rates (10 and 50 mg/mL) and three temperatures (-22 degrees C, 5 degrees C, room temperature). The solutions, which had been initially frozen, were thawed at room temperature or by exposure to microwave radiations. The stability of each sample was determined by a quantitative bacteriological agar gel diffusion assay and by high-performance liquid chromatography. The results of this study indicate that admixtures of ceftriaxone disodium at the concentration rates tested can be frozen for six months without a significant loss in antibiotic activity. At room temperature, the stability is dependent on the concentration of ceftriaxone disodium. At 5 degrees C, the stability is related to the concentration of ceftriaxone and of the solvent. The results obtained by both analytical methods are very close. In order to perform routine assays, the high-performance liquid chromatography method was chosen on the basis of its rapidity and reproducibility.