Each of the three injections consists of 5 mg of morphine (1.0 mL of 5 mg/mL solution). The HYLENEX injection will be 1 mL of 150 units. Although the IV administration will not be blinded, the two SC injections will be double-blinded, using the same volume of normal saline (0.9% sodium chloride) placebo (1.0 mL) as HYLENEX.