Co-delivery of terbinafine hydrochloride and urea with an in situ film-forming system for nail targeting treatment

Investigation on Utility of Some Novel Terpenes on Transungual Delivery of Terbinafine for the Management of Onychomycosis

INTRODUCTION

Onychomycosis is a fungal disorder of the nail which afflicts 5% of the population worldwide. The disease is strenuous to cure as it is chronic, hard to eliminate and tends to recur. Topical therapy is at the forefront for the treatment of many disorders of nail. However, the success rate of topical therapy has been halted owing to the poor permeation of topical therapeutics across densely keratinized nail barrier. Therefore, ungual drug permeation must be improved for an effective topical therapy. An approach to achieve this goal would be the use of terpenes from natural sources as potential penetration enhancers.

OBJECTIVE

This study is aimed to explore the effectiveness of some novel terpenes as potential penetration enhancers on transungual delivery of terbinafine.

METHODS

Ex-vivo permeation studies were performed by sopping the nail clippings of healthy human volunteers in control and working solutions containing terbinafine (5mg/ml) per se and terbinafine (5mg/ml) with 6% of each terpenes including lavandulol, safranal, rose oxide, limonene, 3-methyl-2-butene-1-ol, and linalool respectively for 48 hours. The terbinafine concentration in nail samples was determined using a HPLC (High Performance Liquid Chromatography method.

RESULTS

Statistical analysis showed that studied terpenes increase transungual penetration of terbinafine in the following order: linalool > rose oxide > 3-methyl-2-butene-1-ol > safranal > limonene > lavandulol acetate. Accordingly, linalool was found to be the most effective penetration enhancer for the transungual delivery of terbinafine.

CONCLUSIONS

It is concluded that linalool can be used as safe and potential penetration enhancer for enhancing the transungual delivery of terbinafine for onychomycosis.

Chitosan Nanoparticles Loaded Poloxamer 407 Gel for Transungual Delivery of Terbinafine HCl

The current study aimed to develop chitosan nanoparticles (CSNP) loaded poloxamer 407 (P407) gel formulation for transungual delivery of terbinafine HCl (TBN). TBN-CSNP were prepared by nanoprecipitation method and optimized by face-centered central composite design (FCCCD). Optimized TBN-CSNP formulation exhibited a spherical shape with hydrodynamic diameter; zeta potential and entrapment efficiency (EE) of 229 ± 5 nm; 37 ± 1.5 mV; and 75 ± 2% respectively. The solid state of TBN and its compatibility with formulation ingredients were confirmed through XRD and FTIR analysis respectively. TBN-CSNP loaded P407 gel exhibited pseudoplastic rheological behavior having a spreadability of 11 ± 2 g·cm/s. The washability study showed that 40 ± 2% of the gel was eroded after washing 12 times. Drug release from TBN-CSNP- and TBN-CSNP-loaded gel was 84 ± 5% and 57 ± 3%, respectively. The cumulative quantity of TBN permeated from TBN-CSNP-loaded P407 gel and TBN-loaded P407 gel was 25 ± 8 and 27 ± 4 µg/cm2, respectively. The nail uptake study showed that 3.6 ± 0.7 and 2.1 ± 0.3 µg of rhodamine was uptaken by the nail following 2 h topical application of TBN-CSNP loaded P407 gel and TBN loaded P407 gel, respectively. Hence, the developed CSNP-based P407 gel formulation can be a potential carrier for transungual delivery of TBN to topically treat onychomycosis.

Simultaneous Physico-Mechanical and In Vivo Assessment towards Factual Skin Performance Profile of Topical Polymeric Film-Forming Systems

Topical film-forming systems (FFS) change drastically after solvent displacement, therefore indicating their skin metamorphosis/transformation as a property of special regulatory and research interest. This paper deals with the lack of suitable characterization techniques, suggesting a set of methods able to provide a comprehensive notion of FFS skin performance. After screening the physico-chemical, mechanical and sensory properties of FFS and resulting films, an elaborate three-phase in vivo study was performed, covering skin irritation, friction and substantivity. Upon removal of 24-hour occlusion, no significant change in erythema index was observed, while the film-former type (cellulose ether, acrylate and/or vinyl polymer) affected transepidermal water loss (TEWL); hydrophobic methacrylate copolymer-based samples decreased TEWL by 40–50%, suggesting a semi-occlusive effect. Although both the tribological parameters related to the friction coefficient and the friction curve’s plateau provided valuable data, their analysis indicated the importance of the moment the plateau is reached as the onset of the secondary formulation, while the tertiary state is still best described by the completion of the film’s drying time. The final part of the in vivo study proved the high in-use substantivity of all samples but confirmed the optimal 4:1 ratio of hydrophobic cationic and hydrophilic polymers, as indicated during early physico-mechanical screening.

Improving Transungual Permeation Study Design by Increased Bovine Hoof Membrane Thickness and Subsequent Infection

Ungual formulations are regularly tested using human nails or animal surrogates in Franz diffusion cell experiments. Membranes sometimes less than 100 µm thick are used, disregarding the higher physiological thickness of human nails and possible fungal infection. In this study, bovine hoof membranes, healthy or infected with Trichophyton rubrum, underwent different imaging techniques highlighting that continuous pores traversed the entire membrane and infection resulted in fungal growth, both superficial, as well as in the membrane’s matrix. These membrane characteristics resulted in substantial differences in the permeation of the antifungal model substance bifonazole, depending on the dosage forms. Increasing the thickness of healthy membranes from 100 µm to 400 µm disproportionally reduced the permeated amount of bifonazole from the liquid and semisolid forms and allowed for a more pronounced assessment of the effects by excipients, such as urea as the permeation enhancer. Similarly, an infection of 400-µm membranes drastically increased the permeated amount. Therefore, the thickness and infection statuses of the membranes in the permeation experiments were essential for a differential readout, and standardized formulation-dependent experimental setups would be highly beneficial.