Background Clobetasol propionate is heavenly and often chronically used to treat topical diseases. It may cause suppression of the hypothalamic-adrenal axis leading to a reduction in circulating cortisol and to physiopathological effects such as hypertension, diabetes and osteoporosis-producing iatrogenic Cushing syndrome.^1–3

Purpose The Regional Laboratory of Quality Control (RLQC) activated by our hospital pharmacy service was engaged in verifying the presence of the drug in a patient who used clobetasol for self-medication to treat vitiligo.

Material and methods A 38-years-old female patient used clobetasol proprionate 0.05% (Clobesol^®) cream for more than a year with a median dose of 90 g/week (45 mg clobetasol/w). She presented at the clinician with a serious case of Cushing syndrome. Cortisol and cortisone blood levels were 6.71 and 2.32 ng/ml respectively (normal range: 80–240 and 7–27). The RLQC developed a new method to determinate clobetasol with LC-MS/MS triple quadrupole in biological samples. The analytical method developed is highly sensible (Limit of Detection: 5 pg) and uses 250 mm x 4.6 mm, 5 um, C18 reversed phase column. The internal standard was D8 deoxycorticosterone 4 ng.

Results Clobetasol was extracted from a haematic sample with solid-solid-liquid-extraction. Although the samples were taken 13 days after drug suspension, the method allowed the verification of the residual presence of the drug with a 0.23 ng/ml concentration, compatible with its chronic use.²

Retention and analysis times of clobetasol were 6.8 and 9.5 min. Cortisol and cortisone plasma concentration were 53.51 and 8.38 ng/ml: these values confirmed the hypothalamic suppression. Also urinary cortisol and cortisone values were normalised since they passed from 3 and 1.05 to 58.03 and 62.38 ug/day.

Conclusion The hospital pharmacy service, with RLQC support, permitted the diagnosis of a difficult case of Cushing syndrome by inappropriate self-medication of clobetasol. Pharmacists and general and clinical specialist doctors should play a more active role in the prevention of the misuse of drugs. The TDM remains a great tool to use for proper drug monitoring of medicines with a low therapeutic index and discover the causes of serious adverse drug reactions. The TDM must adopt analytical methods of high sensitivity and specificity in order to qualify its contribution.

References and/or Acknowledgements 1. Tempark T. Endocr2010;38:328–334.

2. Sparidans RW. J Chrom B2010;878:2150–2154.

3. Golubovic LB. Rapid. Comm. Mass. Spectrom2015;29:2319–2327.

No conflict of interest