Fluorophotometric measurement of the buffering action of human tears in vivo

Yamada, Masakazu; Kawai, Masahiro; Mochizuki, Hidetaka; Hata, Yuka; Mashima, Yukihiko

doi:10.1076/ceyr.17.10.1005.5239

Cited by 24 publications

(7 citation statements)

References 11 publications

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“…Unimodal distribution was always observed (Figure 1a). pH of both formulations falls within the range 6.5–9 avoiding discomfort at the time of application [43,44]. The surface tension of ACZ-LP was significantly lower than that ACZ-LP-P ( p < 0.05).…”

Section: Resultsmentioning

confidence: 99%

Osmoprotectants in Hybrid Liposome/HPMC Systems as Potential Glaucoma Treatment

Gómez-Ballesteros¹,

López-Cano²,

Bravo‐Osuna

et al. 2019

Polymers

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The combination of acetazolamide-loaded nano-liposomes and Hydroxypropyl methylcellulose (HPMC) with similar components to the preocular tear film in an osmoprotectant media (trehalose and erythritol) is proposed as a novel strategy to increase the ocular bioavailability of poorly soluble drugs. Ophthalmic formulations based on acetazolamide-loaded liposomes, dispersed in the osmoprotectant solution (ACZ-LP) or in combination with HPMC (ACZ-LP-P) were characterized and in vivo evaluated. The pH and tonicity of both formulations resulted in physiological ranges. The inclusion of HPMC produced an increment in viscosity (from 0.9 to 4.7 mPa·s. 64.9 ± 2.6% of acetazolamide initially included in the formulation was retained in vesicles. In both formulations, a similar onset time (1 h) and effective time periods were observed (7 h) after a single instillation (25 μL) in normotensive rabbits’ eyes. The AUC0–8h of the ACZ-LP-P was 1.5-fold higher than of ACZ-LP (p < 0.001) and the maximum hypotensive effect resulted in 1.4-fold higher (p < 0.001). In addition, the formulation of ACZ in the hybrid liposome/HPMC system produced a 30.25-folds total increment in ocular bioavailability, compared with the drug solution. Excellent tolerance in rabbits’ eyes was confirmed during the study.

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Section: Resultsmentioning

confidence: 99%

Osmoprotectants in Hybrid Liposome/HPMC Systems as Potential Glaucoma Treatment

Gómez-Ballesteros¹,

López-Cano²,

Bravo‐Osuna

et al. 2019

Polymers

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“…The pH of tears usually lies within the range 7.2-7.6 but may be higher on prolonged eye-opening through loss of CO 2 ; the value in neonates is about 6.8. Tears exert a buffering action due to their content of bicarbonate ion, proteins and other components, although the turnover rate has also been shown to be part of the response to pH challenge [17].…”

Section: Saltsmentioning

confidence: 99%

The Normal Tear Film

Tiffany

2008

Developments in Ophthalmology

192

136

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“…Normal tears have a pH between 6.9 and 7.5 [48]. The literature indicates that the ocular instillation of 20 μ L of a buffered solution at pH 5.5, 0.067 M is quickly brought to pH 6–6.5 in the tears [49]. Furthermore, it is usually known that a low pH is well tolerated if it is rapidly brought back to normal tear pH [50], therefore it can be assumed that buffering is not so important.…”

Section: Formulation Developmentmentioning

confidence: 99%

Successfully Improving Ocular Drug Delivery Using the Cationic Nanoemulsion, Novasorb

Lallemand¹,

Daull²,

Benita

et al. 2012

Journal of Drug Delivery

257

223

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Topical ophthalmic delivery of active ingredients can be achieved using cationic nanoemulsions. In the last decade, Novagali Pharma has successfully developed and marketed Novasorb, an advanced pharmaceutical technology for the treatment of ophthalmic diseases. This paper describes the main steps in the development of cationic nanoemulsions from formulation to evaluation in clinical trials. A major challenge of the formulation work was the selection of a cationic agent with an acceptable safety profile that would ensure a sufficient ocular surface retention time. Then, toxicity and pharmacokinetic studies were performed showing that the cationic emulsions were safe and well tolerated. Even in the absence of an active ingredient, cationic emulsions were observed in preclinical studies to have an inherent benefit on the ocular surface. Moreover, clinical trials demonstrated the efficacy and safety of cationic emulsions loaded with cyclosporine A in patients with dry eye disease. Ongoing studies evaluating latanoprost emulsion in patients with ocular surface disease and glaucoma suggest that the beneficial effects on reducing ocular surface damage may also extend to this patient population. The culmination of these efforts has been the marketing of Cationorm, a preservative-free cationic emulsion indicated for the symptomatic treatment of dry eye.

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Fluorophotometric measurement of the buffering action of human tears in vivo

Abstract: Our results suggest that the neutralization process of tears largely depends on the tear turnover rate. The buffering action of tears in vivo consists of the tear turnover as well as its chemical buffering capacity.

Cited by 24 publications

References 11 publications

Osmoprotectants in Hybrid Liposome/HPMC Systems as Potential Glaucoma Treatment

Osmoprotectants in Hybrid Liposome/HPMC Systems as Potential Glaucoma Treatment

The Normal Tear Film

Successfully Improving Ocular Drug Delivery Using the Cationic Nanoemulsion, Novasorb

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