Rheological Characterization of Topical Carbomer Gels Neutralized to Different pH

Abstract

Purpose. The primary objective of this study is to perform detailed and extensive rheological characterization of rheology of carbomer (Carbopol) microgels formulated using a solvent system typically used in topical gel formulations. Solvents like glycerin and propylene glycol can alter rheology and drug delivery characteristics of topical gels owing to their different viscosities and due to the change in solvent-polymer and solvent-solvent interactions. Methods. Aqueous gels with different pH were prepared by dissolving cross-linked Carbopol polymers in a co-solvent system comprising water, propylene glycol, and glycerol and subsequently neutralizing the carboxylic groups of the polymers with triethanolamine (TEA). Oscillatory, steady, and transient shear measurements were performed to measure viscoelastic properties, temperature dependency, yield strength, and thixotropy of carbomer pharmaceutical gels. Results. The topical pharmaceutical gels exhibit remarkable temperature stability. Flow curves obtained at different temperatures indicate Carbopol microgels show much more pseudoplastic behavior (lower power law index) compared to Carbopol gels dissolved only in water. Substantial yield strength is required to break the microgel network of the topical gels. The gel samples exhibit modest thixotropy at higher deformation rates. Conclusions. The rheological behavior of the Carbopol microgels do not change appreciably in the pH range 5.0-8.0, and the gels can be used as effective dermatological base for topical applications.

Casearia sylvestris Improved Cutaneous Burn Repair in Diabetic Rats

“…C. sylvestris was incorporated into the Carbopol gel, since it presents adequate solubility, bioadhesive properties and the important characteristic of compatibility with many excipientes and does not interfere with the active of the crude extract used [38]. On the other hand it can be used as a vehicle for different herbal medicines since it does not interfere with its properties [39].…”

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“…Among the advantages of gels based on carbopol, there is thermal, chemical, and microbiological stability, high viscosity even at low concentrations of polymer, significant emulsifying and suspensive properties, compatibility with most medicines, a significant bioadhesion, providing high bioavailability and prolongation of pharmaceutical effects, etc. [35][36][37][38][39][40] When planning the design of pharmaceutical preparations in the form of gels based on carbomers must be considered the different factors such as the type of carbomer, nature of the alkaline agent, and the ratio between the alkaline agent and carbomer, which influence on the pH and the rheological parameters of gels. The rheological parameters of gels based on carbomers little dependent on temperature; drugs remain gel-like consistency at high temperatures.…”

Development and Evaluation of a Novel Intranasal Spray for the Delivery of Amantadine

“…Therefore, upon heating the values of n will be lower in for stronger gels due to an increase in the noncovalent forces of between neighbouring particles 56 .…”