Melatonin in doctors and nurses working nightshifts-the MIDNIGHT trial

The MIDNIGHT (Melatonin in doctors and nurses working nightshifts) trial was a randomised, placebo-controlled, double-blinded, cross-over pilot study to investigate the feasibility and acceptability of administration of exogenous melatonin (as Circadin) in medical and nursing staff working night shifts. Volunteers were randomised to receive 6 mg Circadin or placebo just before sleeping, after each of three consecutive night shifts. At the next set of shifts, at 4–6 weeks later, subjects received melatonin if they previously had placebo and vice versa. The target recruitment of 25 participants completing both arms of the study was achieved. Twelve participants (nine female/three male) received placebo followed by melatonin and 13 (eight female/five male) received melatonin first. All participants reported taking their trial medication and this concurred with drug accountability. Melatonin was not found in serum during the placebo phase. During the melatonin phase, median levels were 117 (10–1225), 83 (10–1430), and 309 (10–1050) pg ml–1, the morning after each of the three shifts, respectively; levels were highest after the third shift (P<0.01), suggesting some accumulation.