Urinary detection of corticosteroid in topical treatment of skin disease by 19F MRS

ObjectiveTo investigate if it was feasible to quantify the renal excretion of topically applied corticosteroids by F-19 MRS.Materials and methodsFive participants, one healthy and four with skin diseases, were treated with ointment containing betamethasone 17-valerate. Urine samples were collected for up to 87h after the initial application. A sample of ointment mixed with urine served as a study control. Organic fractions were obtained after sample freeze drying, and resolved in deuterated chloroform prior to acquisition of F-19 MR spectra at 470MHz for typically 8 h.ResultsWe detected fluorine signals in 40 of the 62 fractions of organic extracts. The corticosteroid was detected in samples from all patients, ranging from 0.1 to 2.8% of the applied steroid. No fluorine signal was obtained in samples from the healthy volunteer.Discussion(19)F MRS can be utilized to detect topically applied corticosteroids in urine. However, more work is required to optimize and control for extraction procedures, complete spectral assignments and reliable quantification.