Table 2.

Plasma melatonin concentrations at different doses

Dose (number of patients)	Time (h)	Median plasma melatonin (range) (pg ml−1)
0.1 μg kg−1 h−1 for 6 h (n = 4)	0	0 (0–38.5)
	1	31 (0–77)
	3	153.3 (145.5–317.5)
	6	393.3 (339.3–554.5)
0.1 μg kg−1 h−1 for 2 h (n = 4)	0	0 (0–0)
	2	203.3 (160–220)
	6	145.4 (110.8–156.8)
	24	71.6 (51.8–79)
0.02 μg kg−1 h−1 for 2 h (n = 6)	0	0 (0)
	2	48.7 (38.8–71)
	4	52 (41–65)
	5	64 (49.5–67)
	6	63 (0–71)
0.01 μg kg−1 h−1 for 2 h (n = 2)	2	54.8 (43.5–66)
	4	110 (110)
	5	103.8 (103.8)
	6	97.5 (97.5)
	24	28 (28)
	48	38.8 (38.8)
0.04 μg kg−1 for 0.5 h (n = 2)	1	58.5 (42–75)
	72	120.3 (110.5–130)
	96	108 (97–118.5)
	336	74.8 (66.5–83)

Lower doses of melatonin infusion (0.02 μg kg⁻¹ h⁻¹ for 2 h, 0.01 μg kg⁻¹ h⁻¹ for 2 h and 0.04 μg kg⁻¹ over 30 min) gave highly variable plasma melatonin concentrations and unreliable estimates of pharmacokinetics in individuals. Not detectable concentrations were taken as 0 pg ml⁻¹.