Objectives: Ketamine is an attractive agent for pediatric procedural sedation. There are limited data on time to discharge comparing intramuscular (IM) vs. intravenous (IV) ketamine. The authors set out to determine whether IM or IV ketamine leads to quicker discharge from the emergency department (ED) and how side effect profiles compare.Methods: All patients who had received ketamine IM or IV at a tertiary children's hospital ED during the 3-year study period (2004)(2005)(2006)(2007) were identified. Prospective sedation registry data, retrospective medical records, and administrative data were reviewed for drug dosages, use of additional agents, time of drug administration to discharge, total ED time (triage to discharge), and adverse events. A subgroup analysis for patients requiring five or fewer sutures (short suture group) was performed.Results: A total of 229 patients were enrolled (60% male) with median age of 2.8 years (IQR = 1.8-4.3 years) and median weight of 15.7 kg (range = 8.7-74 kg). Ketamine was most frequently employed for laceration repair (80%) and foreign body removal (9%). Overall, 48% received ketamine IM and 52% received it IV. In the short-suture subgroup, 52% received ketamine IM, while 48% received it IV. Multivariate linear regression analysis determined time from drug administration to patient discharge as 21 minutes shorter for IV compared with IM administration, adjusted for age and number of additional doses (R 2 = )0.35; 95% CI = )0.5 to )0.19; p < 0.001). Total time in the ED (triage to discharge) comparing IV versus IM administration, adjusting for age and gender and number of additional doses, was not significantly different (p = 0.16). In the short-suture subgroup, time to discharge from administration was also shorter in the IV ketamine group (R 2 = )0.454; 95%CI = )0.66 to )0.25; p < 0.001) but similar for total time in ED (p = 0.16). Overall, adverse events occurred in 35% (95% CI = 27% to 45%) of the IM group and 20% (95% CI = 13% to 28%) of the IV group (p = 0.01). Only one patient required brief bag-mask ventilation. Conclusions:In this institution, time from drug injection to discharge was shorter in the IV compared to IM ketamine group, both overall and for the short-suture group. However, time from triage to discharge was similar.