Improvement of In Vitro Dissolution of the Poor Water-Soluble Amlodipine Drug by Solid Dispersion with Irradiated Polyvinylpyrrolidone

The aim of this study was to increase both the rates of dissolution and bioavailability of the amlodipine (Amlo) drug. Due to the low cost, high solubility, and amorphous state, polyvinylpyrrolidone (PVP) has been used as a drug carrier in the solid dispersion process. Through applying an irradiation technique, powder of (PVP) is irradiated with six 0-50 kGy irradiation doses. The six irradiated (PVP) samples were characterized using gel permeation chromatography, electron spin resonance, and Fourier transform infrared (FT-IR) spectroscopy. The formulation of six (PVP/Amlo) samples at a ratio of 2:1 wt/wt were characterized using FT-IR spectroscopy and X-ray powder diffraction. In vitro dissolution of (Amlo) drug was assessed in a water solvent at pH 1.2 and pH 7. Results demonstrated that there is a change in the physicochemical properties of irradiated (PVP). FT-IR confirmed that there is an intermolecular H bond between the (Amlo) drug and (PVP) polymer. XRD confirmed that (PVP) changes the crystalline (Amlo) to amorphous amlodipine. Irradiated (PVP) at a dose of 20 kGy released approximately 89% from 40 mg of (Amlo) in 60 s. The in vitro rate of amlodipine dissolution depends on the drug-polymer intermolecular H bond. The rate of (Amlo) dissolution is increased due to the drug-drug intramolecular hydrogen bonding replaced with the drug-polymer intermolecular hydrogen bonding, which reduces the crystal packing. Irradiated (PVP) improved the rate of (Amlo) dissolution compared to unirradiated (PVP).

Understanding the regioselectivity of Michael addition reactions to asymmetric divinylic compounds

In the present paper, we describe the synthesis of novel monomers prepared by regioselective Michael addition to asymmetric divinylic compounds.

From N-vinylpyrrolidone anions to modified paraffin-like oligomers via double alkylation with 1,8-dibromooctane: access to covalent networks and oligomeric amines for dye attachment

The double alkylation of N-vinylpyrrolidone (N-VP) with 1,8-dibromooctane yields paraffin-like oligomeric chains bearing polymerizable vinyl moieties. These oligomers were radically crosslinked in bulk with N-VP as co-monomer yielding swellable polymer disks. The vinylic side groups of the N-VP oligomers allow thiol–ene click reactions with 2-aminoethanethiol hydrochloride to obtain reactive amino-functionalized oligomers. Further modification of the free amino groups with 1,4-difluoro-9,10-anthraquinone (DFA) yields red-colored oligomeric anthraquinone dyes. The final reaction of DFA-substituted N-VP oligomers with Jeffamine^® M 600 leads to blue-colored and branched oligomers with poly(ethylene glycol) side chains.