Discussion

This prospective randomized controlled trial compared the analgesic efficacy of IV lidocaine with IV ketorolac in adult patients presenting to the ED with suspected renal colic. The study demonstrated that IV lidocaine achieved successful pain relief in a higher proportion of patients than IV ketorolac (68.9% vs. 60.0%); however, the difference was not statistically significant (p = 0.378). These findings suggest that IV lidocaine provides analgesia comparable to ketorolac and may be considered a reasonable alternative in appropriately selected patients.

Renal colic is one of the most painful conditions encountered in emergency medicine, and prompt pain relief remains the primary objective of management [1,2]. Current international guidelines recommend NSAIDs as first-line therapy because they reduce prostaglandin synthesis, thereby decreasing ureteric edema, smooth muscle spasm, and renal pelvic pressure [1,2,5]. Ketorolac is widely used because of its rapid onset of action and favorable efficacy profile. Nevertheless, NSAIDs are unsuitable for some patients because of contraindications such as chronic kidney disease, gastrointestinal bleeding, peptic ulcer disease, or cardiovascular disorders [5,6]. Identifying effective non-opioid alternatives is therefore of considerable clinical importance.

The findings of the present study are consistent with previous reports evaluating IV lidocaine for renal colic. Soleimanpour et al. demonstrated that IV lidocaine provided analgesia comparable to IV morphine and significantly reduced pain in patients presenting with renal colic [9]. Similarly, Sin et al. reported favorable analgesic outcomes following IV lidocaine administration in the ED [10]. More recently, Motov et al. observed that IV lidocaine, either alone or in combination with ketorolac, may be an effective opioid-sparing strategy for the management of suspected renal colic [11]. Our findings support these observations and suggest that IV lidocaine can provide clinically meaningful pain relief comparable to standard NSAID therapy.

The analgesic effects of IV lidocaine are believed to result from blockade of voltage-gated sodium channels, suppression of ectopic neuronal activity, and modulation of central pain pathways [7,8]. Unlike NSAIDs, lidocaine does not inhibit prostaglandin synthesis and therefore may represent a useful treatment option for patients in whom NSAIDs are contraindicated. Furthermore, IV lidocaine has demonstrated efficacy in a variety of acute and chronic pain conditions, supporting its role as a non-opioid analgesic in carefully selected patients [7,8,12].

Both treatment regimens were generally well tolerated in the present study. Three patients receiving IV lidocaine experienced transient dizziness, while two patients treated with ketorolac developed mild hypersensitivity reactions that resolved with standard treatment. No serious adverse events were observed in either group. Although the study was not powered to detect differences in safety outcomes, these findings are consistent with previous reports demonstrating that IV lidocaine has an acceptable safety profile when administered at recommended doses with appropriate patient selection and monitoring [9,12].

The present study has several strengths. It employed a prospective randomized controlled design, enrolled patients using clearly defined eligibility criteria, and compared two commonly used non-opioid analgesic strategies in a real-world ED setting. The standardized treatment protocol also reduced variability in patient management, thereby improving the reliability of the findings.

Several limitations should also be acknowledged. First, this was a single-center study with a relatively small sample size, which may have limited the statistical power to detect modest differences between treatment groups. Second, detailed serial pain scores beyond the primary outcome were unavailable, preventing a more comprehensive analysis of pain reduction over time. Third, patients were observed only during their ED stay, and long-term outcomes, recurrence of pain, and patient satisfaction were not evaluated. Finally, although randomization reduced selection bias, the absence of blinding may have introduced the potential for observer bias.

Future multicenter randomized controlled trials with larger sample sizes, standardized serial pain assessments, and longer follow-up are required to further establish the comparative efficacy and safety of IV lidocaine in patients with acute renal colic. Studies evaluating patient-reported outcomes, cost-effectiveness, and the role of IV lidocaine in patients with contraindications to NSAIDs would also provide valuable evidence for clinical practice.

Overall, the findings of this study suggest that IV lidocaine offers analgesic efficacy comparable to IV ketorolac for the management of suspected renal colic in the ED. Given its favorable short-term safety profile and potential role as an opioid- and NSAID-sparing analgesic, IV lidocaine may be considered a useful alternative in appropriately selected patients.

Study limitations

This study has several limitations. First, the sample size was determined pragmatically during the study design phase and was not based on a formal a priori calculation using predefined assumptions regarding effect size, significance level, and statistical power. Consequently, the study may have been underpowered to detect modest differences between the treatment groups and was not designed to demonstrate equivalence or non-inferiority between IV lidocaine and ketorolac. Therefore, the absence of a statistically significant difference should not be interpreted as evidence of equivalent efficacy.

Second, the diagnosis of renal colic was based on the patients' clinical presentation and the treating physician's clinical assessment in the ED. Although patients subsequently underwent imaging investigations, including CT kidneys, ureters, and bladder (KUB) or ultrasonography as clinically indicated, these follow-up data were not collected as part of the study. Consequently, some participants may not have had radiologically confirmed renal colic.

Finally, patients with contraindications to NSAIDs or IV lidocaine, including those meeting our predefined exclusion criteria, were excluded from the study. As a result, the findings may not be generalizable to these patient populations, and the prevalence of such subgroups could not be determined. Future adequately powered multicenter randomized controlled trials with standardized diagnostic confirmation and inclusion of patients with contraindications to NSAIDs are warranted to validate and extend these findings.