Sustained Ocular Drug Delivery from a Temperature and pH Triggered Novel In Situ Gel System

Polysaccharides as Excipients for Ocular Topical Formulations

“…Transcorneal permeation was studied ex vivo using excised goat corneas. The authors report a larger drug amount permeated after 4 h with the in situ gelling system (63.41±2.6%) as compared with the plain drug solution (42.11±2.1%) (Gupta et al, 2007) . They ascribe this difference to a permeabilizing action of Ch on the cornea, on the basis of the renown of Ch as a transmucosal permeation enhancer.…”

“…Then factors other than corneal permeability might contribute to the difference. Ocular irritation was tested by the chick embryo chorioallantoic membrane test (Gupta et al, 2007). It was found that the in situ gel formulation is nonirritant to mildly irritant and is well tolerated.…”

“…On the other hand the in situ gel formulation cleared slowly and no radioactivity was observed in kidney and bladder. This behaviour was ascribed to the known bioadhesivity of Ch and to the gelation that was induced by Ch and Pluronic F-127 (Gupta et al, 2007). Another in situ gel-forming solution was obtained by coupling poly(N-isopropylacrylamide) (PNIPAAm), a well-known thermosensitive polymer having a thermoreversible phase www.intechopen.com transition temperature close to human body surface (Maeda et al, 2006;Taylor & Ceranaowski, 1975;Hsiue et al, 2002;Hsiue et al, 2003), with Ch with the hope that this novel polymer (PNIPAAm-Ch) might couple the advantages of Ch and PNIPAAm (Cao et al, 2007).…”

“…In the light of the discussion so far, the remarkable promotion of the transcorneal absorption of ofloxacin by TMC (Di Colo et al, 2004a) is ascribable to a polymer action on the mucous layer covering the cornea and/or on the corneal cell membrane, rather than to an effective opening of the tight junctions in all layers of corneal cells. To overcome the bioavailability problems associated with the administration of conventional eye drops the use of in situ gel-forming systems that are instilled as drops into the eye and undergo a sol-gel transition in the cul-de-sac has been proposed (Gupta et al, 2007). Different combinations of Ch (MW 150 kDa, 75-85% deacetylated) and poloxamer (Pluronic F-127) were evaluated for gelling ability and viscosity.…”

Newer Trends in In Situ Gelling Systems for Controlled Ocular Drug Delivery

“…Gupta et al [45], developed temperature and pH-triggered in situ ocular delivery system of timolol maleate using Pluronic F127 and chitosan as thermosensitive and pH-sensitive polymers, respectively. The formulation was a clear, isotonic solution that converted into the gel above 35°C and pH 6.9-7.0.…”