Effect of the Curvature of the Punches on the Shape of the Interface and the Delamination Tendency of Bilayer Tablets.

Bilayer tablets are of special interest in the pharmaceutical industry. The main problem during their manufacturing is the occurrence of delamination during or after the ejection from the die. This work studies the influence of using punches with a curvature on the interfacial strength and thus on the delamination tendency of bilayer tablets. Bilayer tablets were produced with a compaction simulator using different flat and concave punches with different radii of curvature. The main compaction pressure was kept constant but the tamping force was varied. Two bilayer model systems were studied. The interfacial strength was determined using a previously described indentation test. The factors studied were analyzed for statistical significance with respect to the responses. The curvature of the interface was found to be higher when the curvature of the punch and the tamping force increased. Breaking tests then demonstrated that, for bilayer tablets obtained using the same compression parameters, the interfacial strength was lower when the curvature of the interface increased. As a consequence, when producing bilayer tablets with concave punches, it is important to choose properly the tableting parameters in order to have an interface between the layers as flat as possible to avoid delamination issues.

Comparison of breaking tests for the characterization of the interfacial strength of bilayer tablets.

The bilayer tableting technology is gaining more acceptance in the drug industry, due to its ability to improve the drug delivery strategies. It is currently assessed by the European Pharmacopoeia, that the mechanical strength of tablets can be evaluated using a diametral breaking tester. This device applies a force diametrically, and records the tablet breaking point. This approach has been used to measure the structural integrity of single layer tablets as well as bilayer (and multi-layer) tablets. The latter ones, however, have a much complex structure. Therefore, testing a bilayer tablet with the currently used breaking test methodology might not be appropriate. The aim of this work was to compare results from several tests that have been proposed to quantify the interfacial strength of bilayer tablets. The obtained results would provide an indication on which tests are appropriate to evaluate the robustness of a bilayer tablet. Bilayer tablets were fabricated using a model formulation: Microcrystalline Cellulose (MCC) for the first layer, and spray dried lactose (SDLac) as second layer. Each set of tablets were tested using the following tests: Diametral Test, Shear Test and Indentation Test. The tablets were examined before and after the breaking test using Scanning Electron Microscopy (SEM). When a bilayer tablet was subjected to shearing or indentation, it showed signs of clear delamination. Differently, using the diametral test system, the tablets showed no clear difference, before and after the testing. However, when examining each layer via SEM, it was clear that a fracture occurred in the layer made of SDLac. Thus, the diametral test is a measure of the strength of one of the two layers and therefore it is not suited to test the mechanical strength of bilayer tablets.

Development and validation of a DESI-HRMS/MS method for the fast profiling of esomeprazole and its metabolites in rat plasma: a pharmacokinetic study.

The advances in pharmaceutical development and drug discovery impose the availability of reliable high-throughput screening methods for the rapid evaluation of drug metabolism and pharmacokinetic (PK) in biological samples. Here, a desorption electrospray mass spectrometry (DESI-MS) method has been developed and validated for the PK profiling of esomeprazole and its metabolites (5-hydroxyomeprazole and omeprazole sulfone) in rat plasma. Rats were treated with an esomeprazole solution (2.5 mg/mL) for endovenous administration and the analyte levels were profiled over 2 h after liquid-liquid extraction from plasma. MS and tandem mass spectrometry (MS/MS) experiments were performed by using a DESI-LTQ-Orbitrap XL instrument and an on-spot fixed time analysis on PMMA surfaces. Validation was performed for the esomeprazole. The DESI-MS/MS method exhibited for the esomepazole excellent sensitivity (limit of detection (LOD)=60 ng/mL), linearity (0.2-20 µg/mL concentration range; y=23848(±361)X, n=15; r(2) =0.987) and precision (RSD<9%) by using an internal standard method. The PK results were discussed in terms of Area Under the Curve, Cmax and Tmax . Data reliability was demonstrated by comparison with a liquid chromatography-tandem mass spectrometry method (p>0.05). The data achieved demonstrated that the DESI-MS method is suitable for sensitive and fast profiling of a drug and its metabolites at the therapeutic concentration levels.

Floating modular drug delivery systems with buoyancy independent of release mechanisms to sustain amoxicillin and clarithromycin intra-gastric concentrations.

Release modules of amoxicillin and clarithromycin combined in a single dosage form designed to float in the gastric content and to sustain the intra-gastric concentrations of these two antibiotics used for the eradication of Helicobacter pylori have been studied. The modules having a disc shape with curved bases were formulated as hydrophilic matrices. Two modules of clarithromycin were assembled by sticking the concave base of one module to the concave base of the other, creating an internal void chamber. The final dosage form was a floating assembly of three modules of clarithromycin and two of amoxicillin in which the drug release mechanism did not interfere with the floatation mechanism. The assembled system showed immediate in vitro floatation at pH 1.2, lasting 5 h. The in vitro antibiotics release profiles from individual modules and assembled systems exhibited linear release rate during buoyancy for at least 8 h. The predicted antibiotic concentrations in the stomach maintained for long time levels significantly higher than the respective minimum inhibitory concentrations (MIC). In addition, an in vivo absorption study performed on beagle dogs confirmed the slow release of clarithromycin and amoxicillin from the assembled system during the assembly's permanence in the stomach for at least 4 h.