 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. The investigators propose a study in healthy volunteers to assess the tolerability and pharmacokinetics of exogenous melatonin and its major metabolites and to relate these doses to ex vivo anti-inflammatory and antioxidant activities. Groups of healthy subjects will receive increasing sequential doses of oral melatonin in an open label dose escalation study. Ex vivo inflammatory responses, oxidative stress and mitochondrial function at concentrations of melatonin identified in the dose escalation study will be determined following exposure of whole blood to an inflammatory insult. This will provide crucial information to inform a subsequent phase II clinical trial of melatonin in patients with sepsis. 