Background The combination of intravenous hydrocortisone and enteral fludrocortisone may reduce mortality in patients with septic shock. The optimal dose and reliability of absorption of fludrocortisone in critically ill patients are unclear.

Methods In a multi-centre, open label, phase II randomized clinical trial, intravenous hydrocortisone alone or in combination with one of three doses of enteral fludrocortisone (50 µg, 100 µg or 200 µg daily) for 7 days was compared in patients with septic shock. The primary outcome was time to shock resolution. We conducted pharmacokinetic studies to assess absorption.

Results Out of 153 enrolled patients, 38 (25%) received hydrocortisone alone, 42 (27%) received additional 50 µg, 36 (24%) received 100 µg and 37 (24%) received 200 µg fludrocortisone. Plasma concentrations of fludrocortisone were detected in 97% of patients at 3 h-median (interquartile range [IQR]) 261 (156–334) ng/L. There was no significant difference in the time to shock resolution between groups with median (IQR) of 3 (2.5–4.5), 3 (2–4), 3 (2–6) and 3 (2–5.5) days in the hydrocortisone alone, 50 µg, 100 µg and 200 µg fludrocortisone groups, respectively. The corresponding 28-day mortality rates were 9/38 (24%), 7/42 (17%), 4/36 (11%) and 4/37 (11%), respectively. There were no significant differences between groups with respect to, recurrence of shock, indices of organ failure or other secondary outcomes.

Conclusions Enteral fludrocortisone resulted in detectable plasma fludrocortisone concentrations in the majority of critically ill patients with septic shock, although they varied widely indicating differing absorption and bioavailability. Its addition to hydrocortisone was not associated with shorter time to shock resolution.