Novel spectral manipulations for determinations of Tolnaftate along with related toxic compounds: Drug profiling and a comparative study.

A comparative study using novel quadruple divisor and mean centering of ratio spectra spectrophotometric methods was developed for resolution of five- component mixture of Tolnaftate, ß-naphthol (Tolnaftate alkaline degradation product and its toxic impurity), methyl(m-tolyl)carbamic acid (Tolnaftate alkaline degradation product), N-methyl-m-toluidine (Tolnaftate toxic impurity) and methyl paraben (as a preservative). For the novel quadruple divisor method, each component in the quinary mixture was determined by dividing the quinary mixture spectrum by a sum of standard spectrum of equal concentration of the other four components as a quadruple divisor. First derivative of each ratio spectra was then obtained which allowed selective determination of each component without interference from other components in the mixture. The second method was mean centering of ratio spectra that depended on utilizing the mean centered ratio spectra in four successive steps leading to enhancement of the signal to noise ratio. The absorption spectra of the five studied components were recorded in the wavelength range of 210-350 nm. The mean centered fourth ratio spectra amplitudes for each component were used for its determination. The developed methods were successfully applied for determination of laboratory prepared quinary mixtures to ensure method's specificity, then, were further applied on Tinea Cure® cream where no interference from excipients. For the first time, Tolnaftate was determined along with its toxic impurity; ß-naphthol, that could be absorbed by the skin, causing systemic toxic effects, unlike Tolnaftate that poorly absorbed, indicating the significance of this work. The proposed methods were statistically compared with each other and with the reference method. Furthermore, ICH guidelines were followed for their validation.

Identification of Hedgehog signaling inhibitors with relevant human exposure by small molecule screening.

In animal models, chemical disruption of the Hedgehog (Hh) signaling pathway during embryonic development causes severe birth defects including holoprosencephaly and cleft lip and palate. The exact etiological basis of correlate human birth defects remains uncertain but is likely multifactorial, involving the interaction of genetic and environmental or chemical influences. The Hh transduction mechanism relies upon endogenous small molecule regulation, conferring remarkable pathway sensitivity to inhibition by a structurally diverse set of exogenous small molecules. Here, we employed small molecule screening to identify human exposure-relevant Hh signaling inhibitors. From a library of 4240 compounds, including pharmaceuticals, natural products, and pesticides, three putative Hh pathway inhibitors were identified: tolnaftate, an antifungal agent; ipriflavone, a dietary supplement; and 17-beta-estradiol, a human hormone and pharmaceutical agent. Each compound inhibited Hh signaling in both mouse and human cells. Dose-response assays determined the three compounds to be 8- to 30-fold less potent than the index Hh pathway inhibitor cyclopamine. Despite current limitations in chemical library availability, which narrowed the scope of this study to only a small fraction of all human exposure-relevant small molecules, three structurally diverse environmental Hh signaling inhibitors were identified, highlighting an inherent pathway vulnerability to teratogenic influences.

Ototoxicity of common topical antimycotic preparations.

OBJECTIVE: To determine the ototoxic effects of five commonly used topical antimycotic agents-clotrimazole, miconazole, nystatin, tolnaftate, and gentian violet-in the guinea pig. DESIGN: A controlled animal study in which the ototoxicity of commonly used topical antifungal agents was investigated by measurement of hair cell loss. METHODS: Several readily available topical antimycotic preparations were instilled into the middle ears of female Hartley guinea pigs over a 1-week period. Two weeks after the last instillation, the animals were euthanized. An active control group was treated with neomycin to confirm the adequacy of the treatment in delivering a known ototoxin; an untreated control group defined the normal distribution of hair cells. The temporal bones were removed, and the cochleas were fixed and dissected. The basilar membranes were examined under the scanning electron microscope. A map of hair cell survival was made for each row in segments of each turn. RESULTS: The untreated control animals had no discernible hair cell loss in the two lower turns. In the apical turn and sometimes the third turn, loss of hair cells was a common finding, this is a known effect of aging in this species. The animals treated with neomycin had damage consistently in the basal turn, sometimes extending into the second turn, as well as the expected hair cell loss in the apical turn. Clotrimazole, miconazole, or tolnaftate did not cause any hair cell loss in the first two turns. Hair cell loss in the third and fourth turns was similar to that of the untreated control group. Likewise, nystatin exhibited no evidence of ototoxicity. Of note, however, the preparation used in this study left a persistent residue in the round window niche. Of the first four animals treated with gentian violet, three developed pronounced behavioral signs of vestibular damage, and three demonstrated extensive middle ear inflammation and extensive new bone growth. Hair cell counts were not attempted because the extreme bone growth interfered with successful perfusion and dissection. CONCLUSIONS: Extrapolating from guinea pigs to humans requires caution. However, it is likely that guinea pigs are, if anything, more susceptible to topical ototoxins than are humans. The specific antimycotics clotrimazole, miconazole, and tolnaftate appear to be safe. Gentian violet has the potential for severe damage. The persistent residue left by the nystatin preparation is cause for concern and is a reminder that both the active ingredient and vehicle must be considered in evaluation of safety.