Modeling of drug release from delivery systems based on hydroxypropyl methylcellulose (HPMC

Modeling of drug release from delivery systems based on
hydroxypropyl methylcellulose (HPMC )

Received 20 October 2000; received in revised form 7 December 2000; accepted 15 December 2000
Abstract
The objective of this article is to review the spectrum of mathematical models that have been developed to describe drug
release from hydroxypropyl methylcellulose (HPMC)-based pharmaceutical devices. The major advantages of these models
are: (i) the elucidation of the underlying mass transport mechanisms; and (ii) the possibility to predict the effect of the
device design parameters (e.g., shape, size and composition of HPMC-based matrix tablets) on the resulting drug release rate,
thus facilitating the development of new pharmaceutical products. Simple empirical or semi-empirical models such as the
classical Higuchi equation and the so-called power law, as well as more complex mechanistic theories that consider
diffusion, swelling and dissolution processes simultaneously are presented, and their advantages and limitations are
discussed. Various examples of practical applications to experimental drug release data are given. The choice of the
appropriate mathematical model when developing new pharmaceutical products or elucidating drug release mechanisms
strongly depends on the desired or required predictive ability and accuracy of the model. In many cases, the use of a simple
empirical or semi-empirical model is fully sufficient. However, when reliable, detailed information are required, more
complex, mechanistic theories must be applied. The present article is a comprehensive review of the current state of the art
of mathematical modeling drug release from HPMC-based delivery systems and discusses the crucial points of the most
important theories
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Modeling of drug release from delivery systems based on
hydroxypropyl methylcellulose HPMC.

Formulation and evaluation of topical pentoxifylline-hydroxypropyl methylcellulose gels for wound healing application

Abstract
Objectives: Oral pentoxifylline shows modest, non-significant effect on the healing rates of chronic wounds. The present research aimed to formulate topical pentoxifylline-hydroxypropyl methylcellulose (HPMC) gels and evaluate their physico-chemical properties, in vitro release characteristics and in vivo wound healing effects. Methods: Six gel formulations containing pentoxifylline (F1-F6) were prepared using HPMC with varying grades and concentrations. The physicochemical properties of gel formulations were evaluated in term of drug content, spreadability, rheological properties, swelling, and release characteristics. The efficacy of optimized formulation was further evaluated using in vivo excision wound models in rats. Results: The spreadability, flow index and swelling percentage of gel formulations ranged 10.71-12.24 gcm/sec, 0.33-0.91 and 148.61-8011.61%, respectively. The rheological study of the prepared formulations exhibited pseudoplastic behavior, which is a characteristic feature of topical gels. Swelling results of F5 and F6 deduced that the cross-linked structures were formed between the polymeric chains. The in vitro drug release profiles of all formulations were found to be followed Higuchi model. The in vivo evaluation performed using rat excision wound model showed significant difference (P < 0.05) in the percentage reduction of wound size between treatment and control groups. The treatment group exhibited complete healing by day 13 as compared with day 15 in the control group. Conclusions: These findings indicated that F5 gel formulation had demonstrated effective release profile for pentoxifylline. The in vivo results confirmed that F5 has pronounced wound healing effects when employed topically.