Melatonin for Prevention of Kidney Injury

Inclusion criteria:

* Aged 18 to 75 years
* Currently prescribed vancomycin with the presumption that therapy will be continued for at least 3 days based on a review of subject status. Because of the critical nature of starting empiric broad-spectrum antibiotics, we will allow one dose of the antibiotic combination before consent and enrollment. This strategy is necessary for the ethical conduct of the study.

Exclusion criteria:

* Estimated creatinine clearance \< 30 mL/min
* Liver impairment (liver enzymes \> 3 times upper limit)
* Any history of allergy or contraindication to melatonin
* Pregnancy or breastfeeding
* Autoimmune disease
* Requiring vasopressors
* Requiring mechanical ventilation
* History of acute kidney injury in the past 30 days
* Inability to take oral medications
* Clinical evidence of significant unstable or uncontrolled illness which, in the opinion of the research team, could confound the results of the study or put the patient at undue risk.