Incorporation of small quantities of surfactants as a way to improve the rheological and diffusional behavior of carbopol gels

Barreiro-Iglesias, Rafael; Alvarez‐Lorenzo, Carmen; Concheiro, Ángel

doi:10.1016/s0168-3659(01)00458-8

Cited by 99 publications

(61 citation statements)

References 45 publications

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“…Once the networks break, this long reorganization period is required for the system to reach equilibrium and form closepacked entangled structure. For 0.5% Carbopol microgels neutralized in solvent water, Barreiro-Iglesis et al (19) reported relaxation times longer than and of the order of 100 s. The increased relaxation times ( 0 > 1000 s) of topical formulations are due to the fact that co-solvent glycerin slowed down the rearrangement processes due to its higher viscosity. Also favorable polymer-cosolvent interactions may cause relaxation time to increase.…”

Section: Low Amplitude Oscillatory Shear Measurementsmentioning

confidence: 99%

Rheological Characterization of Topical Carbomer Gels Neutralized to Different pH

et al. 2004

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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.

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Section: Low Amplitude Oscillatory Shear Measurementsmentioning

confidence: 99%

Rheological Characterization of Topical Carbomer Gels Neutralized to Different pH

et al. 2004

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“…7 The surfactants, on the other hand, act through hydrophobic interaction between the nonpolar surfactant tail and the polymer backbone or solvent, and through electrostatic interactions between the polar heads of the surfactant and the charged group of the polymers. 7 Depending on the choice of the polymer and solvent, one or both mechanisms is responsible for gel formation. When the polymers uncoil because of the formation of hydrogen bonds or electrostatic interaction, the gel structure is formed.…”

Section: Introductionmentioning

confidence: 99%

“…10 These interactions can significantly affect the medicament diffusion from the gel to skin for transdermal delivery of drugs. 7 This is especially important in case of topical gels because the interaction may change during solvent evaporation when the gel is applied on skin. Also the bioavailability of drugs changes owing to solvent evaporation.…”

Section: Introductionmentioning

confidence: 99%

Fourier transform infrared spectroscopy for the analysis of neutralizer-carbomer and surfactant-carbomer interactions in aqueous, hydroalcoholic, and anhydrous gel formulations

Islam

Rodrı́guez-Hornedo

Ciotti

et al. 2004

AAPS J

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The objective of the present study is to evaluate the polymersurfactant and polymer-neutralizer interactions in topical aqueous, anhydrous, and hydroalcoholic gel formulations using Fourier transform infrared (FTIR) spectroscopy. The gels were prepared by dispersing Carbomer (Carbopol 980) in water and ethanol for aqueous and anhydrous systems, respectively. Glycerol and propylene glycol were also added to ensure that the compositions of gels closely resembled those used in typical topical gel formulations. Comparisons of the spectra of Carbopol dispersions in aqueous, anhydrous, and hydroalcoholic systems, performed for the first time, show Carbopol-neutralizer and Carbopol-surfactant interactions vary depending on the nature of the solvents used for gel formation. Analysis of the spectra of aqueous gel formulations indicates significant presence of ionized carboxyl groups only at higher pH (~8.0). Drying of the aqueous gels causes a shift in the carbonyl stretch band toward higher energy, suggesting changes in polymer-neutralizer interaction. Anhydrous gels exhibit 2 different carbonyl stretch bands: the one at ~1653 cm -1 is related to the carboxyl group that is hydrogen bonded and is akin to hydrous gels; the second one at ~1717 cm -1 is indicative of free carbonyl groups. The carbonyl bands of dried gels appear at different energy levels than the solvated gels. This shift resulting from solvent evaporation, reported for the first time, indicates changes in hydrogen bond characteristics. The results show that FTIR can be a good technique compared with other more time-consuming means of analysis for topical formulations.

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“…55, No. 8 19) and by the diameter and distribution of the polymer bed pores described by Hoffman 8) as the environment tortuosity coefficient. Free volume of the matrix as well as the environment tortuosity coefficient depend on the polymer concentration and its cross-linking.…”

Section: Discussionmentioning

confidence: 99%

The Effect of Methylcellulose on Metronidazole Release from Polyacrylic Acid Hydrogels

Musiał

2007

CHEMICAL & PHARMACEUTICAL BULLETIN

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Topical treatment of acne rosacea, a chronic condition characterized by recurrent course for many years, is primarily based on metronidazole preparations. This is the first compound authorized by FDA for local acne rosacea therapy.1) Majority of patients respond to oral administration of an antibiotic complemented with topical application of metronidazole. The available metronidazole products involve 0.75-2% ointments and gels.2) To achieve good compliance, metronidazole products need to be characterized by prolonged release of the compound, which can be achieved, for instance, by binding the drug in a polymer bed, although, the amount of drug released should enable bactericidal activity of metronidazole. Numerous reports have been devoted to the study of interaction between polyacrylic acid and various drugs or polymers, such as polyvinylpyrrolidine or carboxymethylcellulose.3-7) The polyacrylates possess an interesting property of water binding in the form of so-called primary bound water, secondary bound water, and bulk water.8-10) The use of polyacrylates or their compositions with methylcellulose as metronidazole carriers in the dermal preparations may provide interesting patterns of release at the site of application. The aim of this study was to evaluate the effect of various acrylic acid polymers, in composition with methylcellulose on metronidazole release rate from hydrogels proposed for the treatment of acne rosacea. ExperimentalMaterials The following materials were used: metronidazole (SigmaAldrich, EU, Poland), acrylic acid polymers: Carbopol 934P, Carbopol 971P, Carbopol 980NF (BF Goodrich, EU, Belgium), and methylcellulose (Methyl Cellulose 4000, Sigma Chemical, EU, Germany), boiled bidistilled water, semipermeable membrane (Membra-Cel ® , MWCO 3500, Serva, U.S.A.), and Statistica 6.0 software.Preparation of Gels All the formulations were prepared using freshly boiled bidistilled water. The composition is listed in Table 1.Monopolymeric methylcellulose gel (No. 1) and Carbopol gels (No. 2-13) were obtained by sprinkling polymers over the surface of metronidazole 0.75% aqueous solution, and leaving them to swell during the process of sedimentation. All the gels were stored at 8°C. Low temperature prompted dissolution of methylcellulose. The decreased temperature effect on Carbopol swelling was not evident. Gels with over 1.00% content of the above polymers were stirred after sprinkling the polymer over the surface of water. Time required for the gels to swell was from 24 to 48 h except for the methylcellulose gel, for which the swelling time was almost 72 h. Formulations consisting of bipolymeric compositions (No. 14-25) were prepared by combining previously prepared monopolymeric gels in a defined weight ratio. After swelling, all the gels were centrifuged at 4000 rpm for 15 min to remove air bubbles.Measurement of Viscosity Viscosity measurements were performed using a Brookfield DV-IIIϩ rotary rheometer and applying 0.5 ml of gel in the measurement chamber. CPE-51 cone was used. Viscosity was i...

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Incorporation of small quantities of surfactants as a way to improve the rheological and diffusional behavior of carbopol gels

Cited by 99 publications

References 45 publications

Rheological Characterization of Topical Carbomer Gels Neutralized to Different pH

Rheological Characterization of Topical Carbomer Gels Neutralized to Different pH

Fourier transform infrared spectroscopy for the analysis of neutralizer-carbomer and surfactant-carbomer interactions in aqueous, hydroalcoholic, and anhydrous gel formulations

The Effect of Methylcellulose on Metronidazole Release from Polyacrylic Acid Hydrogels

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