Asare-Addo, Kofi, Conway, Barbara R., Larhrib, Hassan, Levina, Marina, Rajabi-Siahboomi, Ali R., Tetteh, John, Boateng, Joshua ORCID: 0000-0002-6310-729X and Nokhodchi, Ali (2013) The effect of pH and ionic strength of dissolution media on in-vitro release of two model drugs of different solubilities from HPMC matrices. Colloids and Surfaces B: Biointerfaces, 111. pp. 384-391. ISSN 0927-7765 (doi:https://doi.org/10.1016/j.colsurfb.2013.06.034)

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Abstract

The evaluation of the effects of different media ionic strengths and pH on the release of hydrochloroth-iazide, a poorly soluble drug, and diltiazem hydrochloride, a cationic and soluble drug, from a gel forming hydrophilic polymeric matrix was the objective of this study. The drug to polymer ratio of formulated tablets was 4:1. Hydrochlorothiazide or diltiazem HCl extended release (ER) matrices containing hypromellose (hydroxypropyl methylcellulose (HPMC)) were evaluated in media with a pH range of1.2–7.5, using an automated USP type III, Bio-Dis dissolution apparatus. The ionic strength of the media was varied over a range of 0–0.4 M to simulate the gastrointestinal fed and fasted states and various physiological pH conditions. Sodium chloride was used for ionic regulation due to its ability to salt out polymers in the mid range of the lyotropic series. The results showed that the ionic strength had a pro-found effect on the drug release from the diltiazem HCl K100LV matrices. The K4M, K15M and K100M tablets however withstood the effects of media ionic strength and showed a decrease in drug release to occur with an increase in ionic strength. For example, drug release after the 1 h mark for the K100M matrices in water was 36%. Drug release in pH 1.2 after 1 h was 30%. An increase of the pH 1.2 ionicstrength to 0.4 M saw a reduction of drug release to 26%. This was the general trend for the K4M and K15M matrices as well. The similarity factor f2 was calculated using drug release in water as a reference.Despite similarity occurring for all the diltiazem HCl matrices in the pH 1.2 media (f2= 64–72), increases of ionic strength at 0.2 M and 0.4 M brought about dissimilarity. The hydrochlorothiazide tablet matrices showed similarity at all the ionic strength tested for all polymers (f2= 56–81). The values of f2 however reduced with increasing ionic strengths. DSC hydration results explained the hydrochlorothiazide release from their HPMC matrices. There was an increase in bound water as ionic strengths increased. Texture analysis was employed to determine the gel strength and also to explain the drug release for the diltiazem hydrochloride. This methodology can be used as a valuable tool for predicting potential ionic effects related to in vivo fed and fasted states on drug release from hydrophilic ER matrices.

Item Type:	Article
Additional Information:	[1] First published online: 25 June 2013. [2] Published in print: 1 November 2013.
Uncontrolled Keywords:	ionic strength, HPMC polymeric matrix tablets, similarity factor, kinetics of drug release, hydration, Diltiazem HCl Hydrochlorothiazide
Subjects:	Q Science > QD Chemistry R Medicine > RS Pharmacy and materia medica
Faculty / School / Research Centre / Research Group:	Faculty of Engineering & Science > School of Science (SCI)
Related URLs:	Publisher Organisation
Last Modified:	17 Oct 2016 09:12
URI:	http://gala.gre.ac.uk/id/eprint/10682

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