Implementation of a spectrofluorimetric method to the determination of 8-methoxypsoralen in capsules and creams used in treatment of psoriasis and vitiligo: An evaluation of the quality of compounding pharmacies in Rio de Janeiro

Abstract

8-Methoxypsoralen is a widely sold drug in Brazil as handled capsules and creams because it is only industrially available as soft gel capsules of 10 mg. In order to contribute to the quality control of these pharmaceutical forms, a spectrofluorimetric method was implemented and applied for the evaluation of the quality of compounding pharmacies in the state of Rio de Janeiro (Brazil). Solutions of 8-methoxypsoralen prepared in ethanol/water (30:70 v/v) produced fluorescence signals at excitation/emission wavelengths of 305/495 nm. The method presented good precision (relative standard deviation, RSD < 4.8%) and recoveries in the pharmaceutical samples from 88.5-108% indicated its feasibility. The results of assay (dosing) and uniformity of content suggested that two of the three evaluated pharmacies did not have appropriate techniques in the preparation of these formulations, which could potentially reduce the efficiency of dermatoses treatment. The implemented method is an alternative to those described in literature for pharmaceutical forms containing 8-methoxypsoralen.