Abstract
Objectives: The present study describes the preparation and evaluation of a Poloxamer 188 (P188)-based thermoreversible gel using Carbopol 934P (C934P) as a mucoadhesive polymer of pseudoephedrine for enhancing the bioavailability and to avoid the first-pass metabolism.
 Materials and Methods: Five formulations (F1-F5) were prepared using cold method. The prepared gels were characterized by pH, drug content, spreadability, mucoadhesive force, gelation temperature, and drug release profile. Thermoreversibility of P188/C934P gel was demonstrated by rheological studies. The drug-polymer compatibility was studied using Fourier transform infrared (FTIR).
 Results: The incorporation of carbopol into P188 gel also reduced the amounts of drug released from the gel formulations. FT-IR studies revealed that there are no interactions between the drug and polymers. Drug content of gels was estimated and the results were found to be satisfactory. In vitro dissolution studies revealed a good drug release from the gels. The drug release was higher in formulations F4 and F5 and lower in F1, F2, and F3 formulations. The order of drug release was found to be F5>F4>F3>F2>F1.
 Conclusion: These findings suggested that developed thermoreversible gels could be used as promising dosage forms to rectal drug delivery for prolonged periods in the management of hemorrhoids.
Highlights
The concept of mucosal adhesion or mucoadhesive was introduced into controlled drug delivery area in the early 1980s, which is a major part of a novel drug delivery system in recent era some of the potential sites for attachment of any mucoadhesive system [1] utilize the property of adhesion of certain water-soluble polymers to buccal cavity, nasal cavity, eyes, vagina, rectal area, sublingual route, and gastrointestinal area
The Fourier transform infrared (FT-IR) spectra of pseudoephedrine, poloxamer, carbopol, and pseudoephedrine loaded in gel formulation are depicted in Fig. 1-5, respectively
The thermoreversibility of Poloxamer 188 (P188)/Carbopol 934P (C934P) gel was verified by various studies
Summary
The concept of mucosal adhesion or mucoadhesive was introduced into controlled drug delivery area in the early 1980s, which is a major part of a novel drug delivery system in recent era some of the potential sites for attachment of any mucoadhesive system [1] utilize the property of adhesion of certain water-soluble polymers to buccal cavity, nasal cavity, eyes, vagina, rectal area, sublingual route, and gastrointestinal area.The utilization of mucoadhesive system is essential to maintain an intimate and prolonged contact of the formulation with the rectal mucosa allowing a longer duration for absorption. The concept of mucosal adhesion or mucoadhesive was introduced into controlled drug delivery area in the early 1980s, which is a major part of a novel drug delivery system in recent era some of the potential sites for attachment of any mucoadhesive system [1] utilize the property of adhesion of certain water-soluble polymers to buccal cavity, nasal cavity, eyes, vagina, rectal area, sublingual route, and gastrointestinal area. Thermoreversibility is a property of certain substance to be reversed when cooled and return to a viscous fluid state when exposed to heat [2]. The rectum provides a relatively constant environment for drug delivery that allows a constant steady-state concentration of drug in plasma and partially avoids gastrointestinal absorption difficulties and hepatic first-pass metabolism [4]
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