Assessment of the nail penetration of antifungal agents, with different physico-chemical properties.

Onychomycosis, or fungal nail infection, is a common fungal infection largely caused by dermatophyte fungi, such as Trichophyton rubrum or Trichophyton mentagrophytes, which affects a significant number of people. Treatment is either through oral antifungal medicines, which are efficacious but have significant safety concerns, or with topical antifungal treatments that require long treatment regimens and have only limited efficacy. Thus, an efficacious topical therapy remains an unmet medical need. Among the barriers to topical delivery through the nail are the physico-chemical properties of the antifungal drugs. Here, we explore the ability of a range of antifungal compounds with different hydrophilicities to penetrate the nail. Human nail discs were clamped within static diffusion (Franz) cells and dosed with equimolar concentrations of antifungal drugs. Using LC-MS/MS we quantified the amount of drug that passed through the nail disc and that which remained associated with the nail. Our data identified increased drug flux through the nail for the more hydrophilic compounds (caffeine as a hydrophilic control and fluconazole, with LogP -0.07 and 0.5, respectively), while less hydrophilic efinaconazole, amorolfine and terbinafine (LogP 2.7, 5.6 and 5.9 respectively) had much lower flux through the nail. On the other hand, hydrophilicity alone did not account for the amount of drug associated with/bound to the nail itself. While there are other factors that are likely to combine to dictate nail penetration, this work supports earlier studies that implicate compound hydrophilicity as a critical factor for nail penetration.

Development and validation of an LC-MS/MS method for determination of methanesulfonamide in human urine.

A sensitive and selective liquid chromatographic method coupled with tandem mass spectrometry (LC-MS/MS) was developed and validated for the quantification of methanesulfonamide (MSA) in human urine. MSA is a potential in vivo metabolite of reparixin, a specific inhibitor of the CXCL8 biological activity. In this study, a simple derivatization procedure with a new reagent, N-(4-methanesulfonyl-benzoyl)-imidazole, was set up to enable MSA and the internal standard (I.S.), ethanesulfonamide (ESA), to be analysed by LC-MS/MS. After derivatization, samples were evaporated and reconstituted in 30% acetonitrile, aq. MSA and I.S. derivatives were separated by reversed phased HPLC (high performance liquid chromatography) on a Luna 5micro C18 column and quantitated by MS/MS using electrospray ionization (ESI) and multiple reaction monitoring (MR M) in the negative ion mode. The most intense [M-H](-) MRM transition of derivatized MSA at m/z 276.2-->197.2 was used for quantitation and the transition at m/z 290.2-->211.2 was used to monitor derivatized ESA. The method was linear over the concentration range from 1 to 100 microg/ml, with a lower limit of quantitation of 1 microg/ml. The intra- and inter-day precisions were less than 5.5% and 10.1%, respectively, and the accuracies were between -4.0% and +11.3%. The method was successfully applied to quantify levels of MSA in human urine after intravenous administration of reparixin to healthy volunteers.