Antioxidant therapy targeted at mitochondria has the potential to reduce inflammation, mitochondrial damage and organ dysfunction in sepsis. Melatonin accumulates in mitochondria and both it and its metabolites have potent antioxidant and anti-inflammatory activity, preventing organ dysfunction in a rat model of sepsis. In a recent Phase I dose escalation study (DAMSEL 1) the investigators showed that oral doses of melatonin in healthy subjects were well tolerated with no adverse events and resulted in levels of circulating melatonin and its major metabolite which had beneficial anti-inflammatory and antioxidant actions in ex vivo studiesStage 1 will assess the pharmacokinetics of melatonin and its major metabolite after a single dose of 50 or 100mg exogenous melatonin in two small groups of patients with sepsis in order to make dosing and dosing interval decisions for Stage 2.