A process for minimizing formation of a highest degradation product during moist heat sterilization of a drug solution of an oxidation susceptible active pharmaceutical ingredient is provided. The oxidation susceptible active pharmaceutical ingredient is mixed with excipients and deoxygenated water to prepare a non-sterile drug solution. The non-sterile drug solution is filled into a moist heat sterilizable flexible infusion bag. The flexible infusion bag with the non-sterile drug solution is terminally moist heat sterilized at a preset air overpressure between about 0.2 bar to about 1.2 bar to obtain a parenteral drug product. The highest degradation product in the parenteral drug product is less than 0.5% by weight of a labeled amount of the oxidation susceptible active pharmaceutical ingredient in the parenteral drug product.
