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

Abstract

Objective: To investigate if it was feasible to quantify the renal excretion of topically applied corticosteroids by 19 F MRS. Materials and methods: Five participants, one healthy and four with skin diseases, were treated with ointment containing betamethasone 17-valerate. Urine samples were collected for up to 87 h 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 19 F MR spectra at 470 MHz for typically 8 h. Results: We 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.