RF06-01 A Novel LC-MS/MS Salivary Fludrocortisone Method With Potential for Monitoring in Adrenal Insufficiency Patients

Abstract M. Dolan: None. D. Marshall: None. J. Hawley: None. B.G. Keevil: None. Fludrocortisone (FC) is a fluorinated exogenous mineralocorticoid used to treat conditions associated with adrenal insufficiency including Addison’s disease and classic congenital adrenal hyperplasia (CAH). The mineralocorticoid action of FC allows the drug to compensate for aldosterone deficiency, thus helping to maintain blood pressure and other homeostatic mechanisms. Optimising FC replacement is vital as under-replacement can cause dizziness and hypotension, whereas over-replacement can lead to cardiometabolic disturbances. Treatment in classic CAH patients, who are typically diagnosed as new-borns, is even more complex as the requirement for mineralocorticoid replacement decreases with age. Endocrine Society guidelines recommend that FC monitoring should involve the clinical assessment of symptoms, which can be non-specific, and regular blood pressure measurements. Plasma renin activity (PRA) should be measured if clinical changes occur, aiming towards the upper end of the reference range. The utility of PRA is debated due to methodological issues and the inherent variability of the analyte itself, which may not always represent FC replacement status. Therefore, investigation into alternative biochemical markers of FC replacement is required. Here we aimed to facilitate this by developing an LC-MS/MS method for the measurement of salivary FC. Method: A salivary FC LC-MS/MS assay has been developed and validated for use according to FDA and EMA guidelines. Passive drool samples from 10 clinical trial patients with classic CAH were collected on two separate occasions at select time points throughout the day (0800, 1200, 1600, 2000 and 2300h). In most patients the 0800h sample was taken pre-FC dose. Once in the laboratory the patient samples were extracted and analysed using the FC method to produce a FC concentration day curve. Results: The method analysis time was 2.1 minutes, with a mean recovery of 102% and limit of quantification of 5 pmol/L (2.1 pg/mL). No analytical interference was identified. Analysis of patient samples using the method showed the presence of FC allowing the production of day curves. In most patients, the pre-dose sample contained no FC, with the subsequent samples showing a peak FC concentration corresponding to the Cmax. After this the FC concentration gradually tapered off throughout the remainder of the day. Conclusions: We have developed a novel assay for the measurement of salivary FC, which may allow the calculation of the area under the curve. As an optimal FC dose has yet to be determined this method may facilitate more in-depth pharmacokinetic studies into FC metabolism and blood pressure control. Thereby identifying patients that are fast metabolisers or poor absorbers of the medication, enabling a non-invasive strategy to optimise patient care. Saturday, June 1, 2024