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).
The effect of the addition of different compatibilizers such as bromobutyl rubber (BIIR) and maleic anhydride (MA) on the elastic behavior of natural rubber=butyl butyl rubber (NR=IIR) blend has been studied by carrying out equilibrium stressstrain measurements for these blends. From the stress-strain curves, Young's modulus was found to have a maximum value at around 5 phr of BIIR and two maxima were observed at 2 and 12.5 phr of maleic anhydride. The modified Mooney-Rivlin equation was used to calculate the parameters C 1 and C 2 . The Song et al. model was tested here to fit the stress-strain curves at both small and large strain, which is capable of accurately describing the mechanical behavior of these blends.
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