According to a randomized controlled clinical trial published in 'International Journal of paediatric dentistry', ketoprofen lysine salt (KLS) was found to be more effective than paracetamol (P) for reducing pain during rapid maxillary expansion (RME).

RME is an orthopaedic procedure used in many clinical conditions. Gianguido Cossellu et al. aimed to compare the effects of KLS and P on pain perception during RME. A total of 151 patients with a mean age of 8.6 years were registered in this prospective randomized controlled clinical trial. The inclusion criteria comprised of prepuberal stage of development, negative posterior transverse interarch discrepancy and the non‐concurrent use of other drugs. In the first phase: Group 1 had 40 patients who used 40mg KLS, Group 2 had 40 patients who used 250mg P and Group 3 had 36 patients in the control group. In the second phase: Group 4 had 35 patients who used 40mg ketoprofen lysine salt once daily for the first 3 days of activation. The numeric pain scale and 100‐mm visual analogue scale was used to reveal about the pain experience. The  Mann‐Whitney test was used to test the pain perception.

The results explained that the pain perception was higher during the first 3 days of activation and it was reported as mild to moderate. Group 1 had significantly less pain during the fourth, fifth, and sixth day as compared to the group 2. During the whole period of RME activation, group 4 reported significantly lower pain. Overall, ketoprofen lysine was more effective than paracetamol in reducing pain.