The second study involved patients undergoing breast resection, or mastectomy with or without axillary resection, with a 1-g dose 20 minutes before the end of surgery and pain followed for 24 hours (reference 13 in Table 1). Although no difference in total morphine use was detected, 42% of IV acetaminophen patients did not receive any morphine, compared with 4% in placebo group. The authors also found that 2 of the 13 patients with more extensive surgical procedures (eg, axillary dissection) that received IV acetaminophen did not request morphine in the first 24 hours postoperatively, whereas all placebo patients did. IV acetaminophen patients did have significantly less pain only at the 1-hour measurement when compared with placebo, but from 2 to 24 hours postoperatively, average pain ratings were below 2.5 in both groups and did not differ.