Abstract: Compositions are provided for formulations of ?-defensin and/or a ?-defensin analog that are highly suitable for parenteral administration. Such formulations provide the ?-defensin and/or a ?-defensin analog in a slightly acidic buffer that includes propylene glycol. Surprisingly, Inventors have found that such formulation increase bioavailability of a ?-defensin and/or a ?-defensin analog so provided by at least a factor of 10 relative to conventional isotonic saline solutions, and that such formulations dramatically improved bioavailability in human subjects relative to animal models. Inventors have also found that such formulations advantageously exhibit low viscosity at high peptide concentrations, reducing injection volume permitting sterilization by simple filtration.