Ketamine Has a Half-Life of 2 ½ Hours

Ketamine has a half-life of 2 ½ hours. If used as a continuous infusion at a dosage of 12.5 mg/hr for postoperative pain relief, how long will it take to achieve a practical steady-state concentration?

A) 5 hours
B) 7 ½ hours
C) 10 hours
D) 12 ½ hours
E) 15 hours