Intravenous Acetaminophen for Renal Colic in the Emergency Department: Where Do We Stand?.

BACKGROUND: The efficacy, safety, opioid-sparing effects, and cost-benefit analyses of intravenous (IV) acetaminophen (APAP) in treating renal colic remain controversial. STUDY QUESTION: To evaluate the safety, efficacy, opioid-sparing effects, and cost-benefits of IV APAP in patients who present with renal colic in the emergency department (ED). DATA SOURCES: We systematically searched PubMed (January 1970 to April 2016). STUDY DESIGN: Randomized controlled trials which evaluated IV APAP for renal colic in the ED were eligible. The clinical outcomes measured were change in pain scores from baseline, incidence of adverse events, use of rescue analgesia, and cost-benefits. Forest plots were constructed using the Mantel-Haenszel method in a random effect model to changes in pain scores from the baseline to designated intervals. RESULTS: The analysis suggested a difference in pain reduction favoring IV APAP over morphine. IV APAP had a significant effect in pain reduction than IV morphine (difference in mean pain score reduction = 7.5 in a 100-point visual analog scale (VAS); 95% confidence interval [CI], 1.99-13.00; P = 0.008). There was mild-to-moderate study heterogeneity (I = 42%). No difference was observed when IV APAP was compared with intramuscular piroxicam for pain reduction (difference in mean pain score reduction = 0.17 in a VAS reduction ≥50% VAS; 95% CI, -0.22 to 0.57) and to intramuscular diclofenac (difference in mean pain score reduction = 0.00 in a numeric rating scale reduction ≥50%; 95% CI, -0.12 to 0.12). The analysis for nonsteroidal anti-inflammatory drugs versus IV APAP revealed no difference (difference in mean pain score reduction = 0.01 in a 100-point VAS; 95% CI, -0.10 to 0.13; P = 0.80). CONCLUSIONS: In this meta-analysis, we found that data on the efficacy, safety, opioid-sparing effects, and cost-benefit analyses of IV APAP for renal colic were weak. Based on the available data, IV APAP should not be considered as an alternative to opioids or nonsteroidal anti-inflammatory drugs for the primary management of renal colic in the ED.