For phenylephrine injections, 1 mL of 1% phenylephrine (10 mg / mL) is added to 19 mL of 0.9% saline to make 500 mcg / mL; 100 to 500 mcg (0.2 to 1 mL) is injected every 5 to 10 minutes until relief occurs or a total dose of 1000 mcg is given.