The use of the S-Caine patch is safe and feasible in children younger than three: A Nonrandomized Clinical Trial

Purpose: Effective pain control in infants and toddlers is challenging, with limited data on topical anaesthetic safety. This study evaluates the safety and feasibility of a single S-Caine patch, a eutectic 70mg lidocaine/70mg tetracaine mixture with heat-assisted delivery, in children under three years. Methods : In this nonrandomized clinical trial (2019–2024) at a single tertiary paediatric centre, 67 of 106 eligible children under three years (median 0.55 years [IQR, 0.13–1.09]; range 3 days–3 years; 58% male) with arterial or central venous catheters received a single S-Caine patch applied for 30 minutes. Primary outcomes were safety, measured by plasma lidocaine concentrations (Cmax) versus a 0.100mg/L safety threshold, adverse events monitoring, and feasibility assessed by Likert scales. Secondary outcomes included subgroup analyses by demographic and procedural factors. Results: Median plasma lidocaine concentrations at −15, 15, 30, 60, 120, and 240 minutes were <0.010, <0.010, 0.018, 0.020, 0.016, and 0.013mg/L, respectively. Median Cmax was 0.025 [0.014–0.038]mg/L, remaining well below the predefined safety threshold across all subgroups (p<0.001). Two patients exceeded the threshold (0.270 and 0.110mg/L) without clinical effects. Minor adverse events occurred in 49 patients (73%): exclusively transient local erythema; resolving or decreasing within 30 minutes. Feasibility was excellent (≥4/5) in 87% at application and 82% at removal. Conclusion: In children under three years, the S-Caine patch is considered safe and feasible, with plasma lidocaine concentrations well below strict clinically relevant thresholds and only minor transient local reactions, supporting its role as a non-invasive analgesic for procedural pain.