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Nm, Davies; Sj, Farr; Hadgraft, Jonathan; Iw, Kellaway

doi:10.1023/a:1015813225804

Cited by 114 publications

(17 citation statements)

References 8 publications

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“…Carbopol is a polyacrylicacid (PAA) polymer, which shows a sol to gel transition in aqueous solution as the pH is raised above its pK a of about 5.5 [10]. Chitosan, an amine-polysaccharide is also pH dependent, cationic polymer.…”

Section: Introductionmentioning

confidence: 99%

Carbopol/Chitosan Based pH Triggered In Situ Gelling System for Ocular Delivery of Timolol Maleate

Gupta¹,

Vyas²

2010

Sci. Pharm.

109

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The poor bioavailability and therapeutic response exhibited by conventional ophthalmic preparations due to rapid precorneal elimination, dilution and nasolacrimal drainage of the drug may be vanquished by the use of in situ gelling systems that are instilled as drops in to the eye and undergo a sol-gel transition in the cul-de-sac. Timolol eye drops may cause systemic side effects in glaucoma patients due to absorption of the drug into systemic circulation. In situ gelling system of this drug can provide localized effect with reduced contraindications, improved patient compliance and better therapeutic index. The present work describes the formulation and evaluation of an ophthalmic delivery system of an antiglaucoma drug, timolol maleate (TM) based on the concept of pH-triggered in situ gelation. Polyacrylic acid (carbopol) was used as the gelling agent in combination with chitosan (amine polysaccharide), which was acted as a viscosity-enhancing agent. Formulations were evaluated for pH, viscosity, gelling capacity and drug content. The 0.4% w/v carbopol/0.5% w/v chitosan based in situ gelling system was in liquid state at room temperature and at the pH formulated (pH 6.0) and underwent rapid transition into the viscous gel phase at the pH of the tear fluid (lacrimal fluid) (pH 7.4). The in vitro drug release and in vivo effects of the developed in situ gelling system were compared with that of Glucomol® (a 0.25% TM ophthalmic solution), 0.4% w/v carbopol solution as well as liposomal formulation. The results clearly demonstrated that developed carbopol-chitosan based formulation was therapeutically efficacious and showed a fickian (diffusion controlled) type of release behaviour over 24 h periods. The developed system is thus a viable alternative to conventional eye drops and can also prevent the rapid drainage as in case of liposomes.

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Section: Introductionmentioning

confidence: 99%

Carbopol/Chitosan Based pH Triggered In Situ Gelling System for Ocular Delivery of Timolol Maleate

Gupta¹,

Vyas²

2010

Sci. Pharm.

109

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“…Many researchers in polymer and pharmaceutical chemistry have developed and utilized various mucoadhesive polymers for TMD systems. [1][2][3][4] Among various synthetic and natural mucoadhesive polymers, poly(acrylic acid) (PAA) has been considered as one of the best mucoadhesive polymers based on its excellent mucoadhesive property. Despite the excellent mucoadhesive property of PAA, it has some drawbacks if used in a TMD system, such as high glass transition temperature (T g ) and high water solubility.…”

Section: Introductionmentioning

confidence: 99%

A novel mucoadhesive polymer prepared by template polymerization of acrylic acid in the presence of poloxamer

Chun

Cho

Choi

2000

J. Appl. Polym. Sci.

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“…Surprisingly, the profiles of both nanoparticle/mucin dispersions were practically identical to each other. There are some reports concerning the poor mucoadhesive properties of PVA 26,27) and an interaction between mucin and PVA layer was not expected. However, it was assumed that the addition of Carbopol to PVA in the mixed phase would provide eventually an interaction of PVA/Carbopol formulated nanoparticles with mucin.…”

Section: Resultsmentioning

confidence: 98%

Influence of the Homogenisation Procedure on the Physicochemical Properties of PLGA Nanoparticles

Vandervoort

Yoncheva

Ludwig

2004

CHEMICAL & PHARMACEUTICAL BULLETIN

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One of the most popular techniques for the preparation of PLGA nanoparticles is emulsification solvent evaporation and its modifications such as the use of a double emulsion for the encapsulation of water soluble drugs. 1,2) In the current study, a homogenisation step was added to the preparation procedure. The effect of the stirring speed used during emulsification on the PLGA particle properties has been extensively examined.3,4) However, high stirring speed and even sonication are often not sufficient to achieve a small particle size and/or a narrow particle size distribution. Therefore, the high-pressure homogenisation technique was successfully adapted.5) This method is mainly used for the production of microemulsions [6][7][8] and liposomes, 9,10) but there is only a limited number of studies concerning polymeric nanoparticle preparations. 11-13)The particle size is, however, an important parameter codetermining the particle distribution and drug release. More specifically for ophthalmic use, it has been observed that large particles may irritate the eye. Consequently, smaller particles are preferred for ophthalmic delivery systems. 14)Additionally, Calvo et al. have reported that poly(e-caprolactone) nanoparticles (0.20-0.25 mm) improve ocular bioavailibility of indomethacin rather than poly(e-caprolactone) microparticles (6 mm).15) Thus, one of the most important characteristics of nanoparticles is their size.The present study aimed to evaluate the feasibility of homogenisation as a tool to adapt the properties of pilocarpine HCl-loaded PLGA nanoparticles. The influence of the homogenisation procedure on the size, the zeta potential value, drug encapsulation and drug release of the particles prepared was studied.The homogenisation parameters studied were the pressure applied, as well as the number of cycles.PLGA particles were prepared using three different stabilisers: polyvinylalcohol (PVA), carbomer (Carbopol 980 NF) and poloxamer (Lutrol F-68). PVA is the reference stabilising agent for the emulsification-solvent evaporation method.3) The feasibility of the use of Carbopol and poloxamer has been demonstrated in earlier work.16) Apart from these three stabilisers, mixtures of PVA and poloxamer as well as mixtures of PVA and Carbopol were also employed.The ocular bioavailibility can be improved using mucoadhesive particulate drug delivery systems.17) Various methods have been developed to evaluate the mucoadhesion of nanoparticulate drug delivery systems. Determination of the detachment force for microspheres from pig intestinal mucosa 18) or from mucus model gel 19) was proposed. Another method was to evaluate the amount of attached or non-adherent nanoparticles after placing on the rat intestinal mucosa. 20)Some authors investigated the behaviour of mucin/bioadhesive polymer dispersions by rheology 21,22) or by turbidimetric measurements.23) Thus, the interaction between mucin and mucoadhesive products caused changes in the viscosity or turbidity of the dispersions. Since these techniques are easily ...

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Untitled

Cited by 114 publications

References 8 publications

Carbopol/Chitosan Based pH Triggered In Situ Gelling System for Ocular Delivery of Timolol Maleate

Carbopol/Chitosan Based pH Triggered In Situ Gelling System for Ocular Delivery of Timolol Maleate

A novel mucoadhesive polymer prepared by template polymerization of acrylic acid in the presence of poloxamer

Influence of the Homogenisation Procedure on the Physicochemical Properties of PLGA Nanoparticles

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