ObjectiveWe wished to determine whether the addition of magnesium sulfate (MgSO4) or lidocaine to diclofenac could improve the analgesic efficacy in emergency department (ED) patients with acute renal colic. MethodsIn this prospective, double-blinded, randomized controlled trial of patients aged 18-65 years with suspected acute renal colic, we randomized them to receive 75 mg intramuscular (IM) diclofenac and then either intravenous (IV) MgSO4, lidocaine, or saline control. Subjects reported their pain using a Numerical Rating Scale (NRS) before drug administration and then 5, 10, 20, 30, 60, and 90 minutes afterwards. Our primary outcome was the proportion of participants achieving at least a 50% reduction in NRS 30 min after drug administration. ResultsWe enrolled 280 patients in each group. A 50% or greater reduction in NRS at 30 minutes occurred in 227 (81.7%) patients in MgSO4 group, 204 (72.9%) in lidocaine group, and 201 (71.8%) in control group, with significant differences between MgSO4 and lidocaine (8.8%; 95% CI [1.89-15.7]; p=0.013) and between MgSO4 and control (9.9%; 95% CI [2.95-16.84]; p=0.004). Despite this, differences between all groups at every time point were below the accepted 1.3 threshold for clinical importance. There were no observed differences between groups in the frequency of rescue analgesics and return visits to the ED for renal colic. There were more adverse events, although minor, in the MgSO4 group. ConclusionAdding intravenous MgSO4, but not lidocaine, to IM diclofenac offered superior pain relief, but at levels below accepted thresholds for clinical importance.
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