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.

Hydroxypropyl Methylcellulose

Polymer partially derived from cellulose. Used in bath products, hair shampoos, and skin cleansers. Is both soluble and insoluble depending on temperature exposure making this ingredient highly versatile.

Hydroxypropyl MethylcelluloseHydroxypropyl Methylcellulose (HPMC), also known as Hypromellose, is semi-synthetic polymer partially derived from cellulose. The polymers are created in response to a chemical reaction between cellulose and ethylene or propylene oxides or it can be developed between cellulose and both of these substances.

It is ommonly used in bath products, hair shampoos, and skin cleansers and is effective as a thickening agent to create gels and serums or as a binding agent. This component can be either soluble or insoluble in water depending on the temperature it is exposed to. When HPMC is exposed to hot water it becomes insoluble, where typically solubility is induced by heat exposure. This makes it excellent additive to lotions and creams. It also helps to produce a silkiness to these products. When exposed to cold temperatures it becomes soluble forming a gel. This consistency is useful in shower gels, shaving gels, and serums. It also capable of producing crystal clear solutions and forms a film upon drying which acts as a protective barrier for the skin.