SPECTROFLUOROMETRIC DETERMINATION OF 5-METHOXYPSORALEN PHARMACOKINETIC IN PATIENTS SERUM

In medicine, psoriasis and vitiligo are most often treated with PUVA t herapy (psoralen plus ultraviolet A). The determination of psoralen in patients' blood is necessary, as it is admitted that the therapeutic efficiency depends on drug concentration in patients' serum. The amoun t of UVA to administer is inversely proportional to serum peak concent ration. High-performance liquid chromatography (HPLC) and gas chromato graphy are the most employed methods for determining psoralens in pati ents' serum. The 2 techniques are precise and very sensitive, but time consuming. The aim of this paper is to propose a suitable method whic h is rapid and simple. It is a spectrofluorimetric technique for 5-met hoxypsoralen (5-MOP) determination in the serum of patients treated wi th PUVA therapy. 5-MOP extraction was carried out with an heptane/ dic hloromethane mixture (4/1; v/v), according to the Stolk method (1980). A calibration curve (CC) was plotted from 5-MOP concentrations (range 50, 100, 200, 300, 400, 500 ng/ml). The CC was linear with a good coe fficient of correlation: r=0.9971, and a suitable coefficient of varia tion (CV) of 7.0%. The recovery of the method ranged from 85.3 +/- 4.2 to 108 +/- 4.1%. The assay precision gave a CV ranging from 0.10 to 6 .90%, with an error inferior to +/-10%. The method did not reveal any interference from serum components on the 5-MOP emission wavelength. T he limit of detection of 5-MOP was 15 ng/ml. The proposed procedure wa s proved to be appropriate for a rapid determination of 5-MOP in patie nts' serum. This technique could also be employed for other psoralens used in PUVA therapy (e.g., 8-methoxypsoralen).