[DOWNLOAD] "Evaluation of Silicone Elastomers for Tablet Coating" by Julia Nahrup Schulze ~ eBook PDF Kindle ePub Free
eBook details
- Title: Evaluation of Silicone Elastomers for Tablet Coating
- Author : Julia Nahrup Schulze
- Release Date : January 19, 2013
- Genre: Science & Nature,Books,Professional & Technical,Medical,
- Pages : * pages
- Size : 14004 KB
Description
The objective of this project was to study the effect of modifications of endhydroxylated poly(dimethylsiloxane) (PDMS) formulations on tablet drug release. Emulsions of crosslinked endhydroxylated PDMS, a novel film-forming polymer, were characterized and investigated for their ability to be applied onto tablet cores in a spray-coating process for controlled drug release. Modifications of the crosslinking agent from the most commonly used tetraethylorthosilicate (TEOS) to the trifunctional 3-(2,3-epoxypropoxy)propyltrimethoxysilane (SIG) and a 1:1-mixture of the two crosslinker were undertaken. Addition of vermiculate clay, copolymeric substances and different channeling-agents were studied. Copolymers of methylpolysiloxane with polyoxyethylene (DC193 and DC5324) or dimethyl,methyl (polyoxyethylene) (DCQ2-5220) as well as poly (acrylamide-co-acrylic acid) were used. Lactose, microcrystalline cellulose (MCC) and polyethyleneglycol 8000 (PEG) were the channeling-agents applied. A change in molecular weight of the PDMS was analyzed. Effects on dispersion properties were characterized by particle size distribution, viscosity and visual observation of phase-separation. Mechanical properties of resulting cast and sprayed films were studied to determine applicability in a pan-coating process. Release of Hydrochlorothiazide (marker-drug) was studied from tablets coated in a lab-size conventional coating pan. Dispersions were found suitable for a spray-coating process. Only the formulation with acrylic-copolymer addition was unstable as phase separation occurred. Preparation of free films showed that methylpolysiloxane-copolymers negatively affected the mechanical properties so that coating onto tablet cores was not possible. Tablets coated with formulations crosslinked using the 1:1-mixture of SIG/TEOS and containing polyethyleneglycol were most suitable to control drug release, at 5% coating weight. Constant release rates were achieved for formulations with up to 25% (w/w of PDMS) PEG; higher amounts resulted in a non-linear release pattern. Upon adding 50% PEG, a drug release of 62% over 24 hours could be achieved. Formulations containing 25 and 50% (w/w of PDMS) PEG were stable for at least 3 months when tested according to ICH-guidelines. In comparison with Eudragit NE (copolymeric product of 2:1 ethylacrylate / methylmethacrylate) PDMS-formulations showed similar mechanical and improved spray-application properties. Addition of channeling agents was necessary for both products to achieve drug release. The effect of polyethyleneglycol was greater on formulations based on PDMS than for Eudragit NE.