Nail lacquer films’ surface energies and in vitro water-resistance and adhesion do not predict their in vivo residence

Sudaxshina Murdan

doi:10.5920/bjpharm.2017.03

Abstract

The in vivo residence of nail lacquers (which are ideal topical drug carriers for the treatment of nail diseases) determines their frequency of application, and is thereby expected to influence patient adherence and success of treatment. Thus in vitro measurements to indicate lacquers’ in vivo residence are routinely conducted during formulation development. However the literature on in vitro-in vivo correlations is severely limited. Thus, the aim of the work discussed in this paper was to investigate correlations between in vivo residence and in vitro film resistance to water, in vitro film adhesion and surface energy of lacquer films. In vivo measurements were conducted on fingernails in six volunteers. Seven commercially available nail lacquers were tested in commonly-used measurements. Correlations between in vivo residence and in vitro water resistance and adhesion were found to be extremely poor. The surface energies of the lacquer films (which were between 33 and 39 mJ/m2) were also not predictive of in vivo residence. High density polyethylene (HDPE) sheet – whose surface energy was determined to be similar to that of the human nailplate – was found to be a suitable model for the nailplate (when investigating surface energy) and was used in a number of experiments.

Highlights

Nail diseases, for example, onychomycosis and psoriasis are common, affecting approximately 14-18% and 1% of the general population respectively (Baran R et al, 2006; Murdan, 2002; Murdan, 2012; Reich, 2009) and demand for their treatment is increasing
Sales for the US dermatophytic onychomycosis market are estimated to grow at a compound annual growth rate of 20% for 2012-2022, which is expected to be partly driven by new efficacious topical medicines (PharmaPoint, 2013)
We conclude that correlations between in vivo residence of nail lacquers and commonly-used in vitro water resistance and film adhesion tests are poor

Summary

Introduction

For example, onychomycosis (fungal infections of the nail) and psoriasis are common, affecting approximately 14-18% and 1% of the general population respectively (Baran R et al, 2006; Murdan, 2002; Murdan, 2012; Reich, 2009) and demand for their treatment is increasing. In addition to in vivo residence, nail lacquer formulations are tested for other properties including flow, brushability, drying qualities, film colour, gloss, thickness, hardness, flexibility, adhesion, mechanical and water resistance (Braunagel, 2005; Schlossman, 1981). As pointed out by Murdan et al (2015) their findings of correlations between in vitro water-resistance and in vivo residence could have been partly predicted by their use of both water-sensitive and water-resistant lacquers in the study. This begs the question of whether the findings would apply if only fairly water-resistant nail lacquers had been tested

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Conclusion