Ocular pharmacokinetics/pharmacodynamics

Worakul, Nimit; Robinson, Joseph R.

doi:10.1016/s0939-6411(97)00064-7

Cited by 102 publications

(58 citation statements)

References 43 publications

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“…Porcine cornea (0.67 mm) mimic human cornea (0.52 mm) anatomically although the former is slightly thicker than the latter (Faber et al, 2008;Worakul & Robinson, 1997). They were directly transported to the laboratory and used within few hours of enucleation.…”

Section: Ex Vivo Permeation Studymentioning

confidence: 99%

Poloxamer-based thermoresponsive ketorolac tromethamine in situ gel preparations: Design, characterisation, toxicity and transcorneal permeation studies

Fathalla

Vangala

Longman

et al. 2017

European Journal of Pharmaceutics and Biopharmaceutics

139

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, Poloxamer-based thermoresponsive ketorolac tromethamine in situ gel preparations: Design, characterisation, toxicity and transcorneal permeation studies, European Journal of Pharmaceutics and Biopharmaceutics (2017), doi: http://dx.doi.org/10. 1016/j.ejpb.2017.01.008 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. AbstractThis study was aimed at preparing, characterising and evaluating in situ gel formulations based on a blend of two hydrophilic polymers i.e. poloxamer 407 (P407) and poloxamer 188 (P188) for a sustained ocular delivery of ketorolac tromethamine (KT). Drug-polymer interaction studies were performed using DSC and FT-IR. The gelation temperature (T sol-gel ), gelation time, rheological behaviour, mucoadhesive characteristics of these gels, transcorneal permeation and ocular irritation as well as toxicity was investigated. DSC and FT-IR studies revealed that there may be electrostatic interactions between the drug and the polymers used.P188 modified the T sol/gel of P407 bringing it close to eye temperature (35 o C) compared with the formulation containing P407 alone. Moreover, gels that comprised P407 and P188 exhibited a pseudoplastic behaviour at different concentrations. Furthermore, mucoadhesion study using mucin discs showed that in situ gel formulations have good mucoadhesive characteristics upon increasing the concentration of P407. When comparing formulations PP11 and PP12, the work of adhesion decreased significantly (P < 0.001) from 377.9 ± 7.79 mN.mm to 272.3 ± 6.11 mN.mm. In vitro release and ex vivo permeation experiments indicated that the in situ gels were able to prolong and control KT release as only 48% of the KT released within 12 h. In addition, the HET-CAM and BCOP tests confirmed the nonirritancy of KT loaded in situ gels, and HET-CAM test demonstrated the ability of ocular protection against strongly irritant substances. MTT assay on primary corneal epithelial cells revealed that in situ gel formulations loaded with KT showed reasonable and acceptable percent cell viability compared with control samples.

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Section: Ex Vivo Permeation Studymentioning

confidence: 99%

Poloxamer-based thermoresponsive ketorolac tromethamine in situ gel preparations: Design, characterisation, toxicity and transcorneal permeation studies

Fathalla

Vangala

Longman

et al. 2017

European Journal of Pharmaceutics and Biopharmaceutics

139

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“…The position of electrode placement was also expected to affect ocular iontophoretic delivery due to the anatomy of the eye-different transscleral routes of penetration and barriers (Cunha-Vaz, 1979;Worakul and Robinson, 1997;Robinson et al, 2006). When the applied electric current is increased, the electric field across the eye from the donor to the return electrodes increases, and iontophoretic delivery is expected to be enhanced.…”

Section: Factors Affecting Transscleral Iontophoresismentioning

confidence: 99%

Examination of penetration routes and distribution of ionic permeants during and after transscleral iontophoresis with magnetic resonance imaging

Molokhia

Jeong

Higuchi

et al. 2007

International Journal of Pharmaceutics

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Previously, transscleral and transcorneal iontophoretic delivery was studied and compared to passive delivery and intravitreal injection using nuclear magnetic resonance imaging (MRI). The objective of the present study was to employ MRI to further investigate the factors affecting transscleral iontophoretic delivery. In the present study, anodal and cathodal constant current transscleral iontophoresis were conducted with excised sclera in side-by-side diffusion cells in vitro and with rabbits in vivo. The total current and duration of application were 2 and 4 mA (current density 10 and 20 mA/cm 2 ) and 20-60 min, respectively. The delivery and distribution of the model permeants manganese ion (Mn 2+ ) and manganese ethylenediaminetetraacetic acid complex (MnEDTA 2− ) into the eye during iontophoresis were determined with MRI and compared with the results obtained in previous studies of subconjunctival injection and passive delivery. Both anodal and cathodal iontophoresis provided significant enhancement in ocular delivery compared to passive transport in the in vitro and in vivo experiments. Transscleral iontophoretic delivery was related to the position and duration of the iontophoresis application in vivo. Permeants were observed to be delivered primarily into the anterior segment of the eye when the pars plana was the application site. Extending the duration of iontophoresis at this site allowed the permeants to be delivered into the vitreous more deeply and to a greater extent than when the application site was at the back of the eye near the fornix. The present results show that electrode placement was an important factor in transscleral iontophoresis, and the ciliary body (pars plana) was determined to be the pathway of least resistance for iontophoretic transport. These new findings continue to support the utility of MRI as a noninvasive technique in ocular drug delivery research and testing.

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“…Due to the complicated anatomy and the separated components of the eye, ocular pharmacokinetics can be complicated, and this has been reviewed in the literature (e.g., 4,5). Important aspects such as the penetration pathways and location of the barriers after subconjunctival injections are not completely clear.…”

Section: Introductionmentioning

confidence: 99%

Assessment of Subconjunctival Delivery with Model Ionic Permeants and Magnetic Resonance Imaging

Molokhia

Jeong

2004

Pharm Res

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Subconjunctival delivery of the ionic permeants in vivo cannot be quantitatively predicted by the in vitro results. MRI is a noninvasive complementary technique to traditional pharmacokinetic methods. It can provide insights into ocular pharmacokinetics without permeant redistribution that can occur in surgical procedure postmortem in traditional pharmacokinetic studies when the blood vasculature barrier is absent.

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Ocular pharmacokinetics/pharmacodynamics

Cited by 102 publications

References 43 publications

Poloxamer-based thermoresponsive ketorolac tromethamine in situ gel preparations: Design, characterisation, toxicity and transcorneal permeation studies

Poloxamer-based thermoresponsive ketorolac tromethamine in situ gel preparations: Design, characterisation, toxicity and transcorneal permeation studies

Examination of penetration routes and distribution of ionic permeants during and after transscleral iontophoresis with magnetic resonance imaging

Assessment of Subconjunctival Delivery with Model Ionic Permeants and Magnetic Resonance Imaging

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