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 70 mg lidocaine/70 mg tetracaine mixture with heat-assisted delivery, in children under 3 years. In this nonrandomised clinical trial (2019–2024) at a single tertiary paediatric centre, 67 of 106 eligible children under 3 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 min. Primary outcomes were safety, measured by plasma lidocaine concentrations (Cmax) versus a 0.100 mg/L safety threshold, adverse events monitoring, and feasibility assessed by Likert scales. Secondary outcomes included subgroup analyses by demographic and procedural factors. Median plasma lidocaine concentrations at − 15, 15, 30, 60, 120, and 240 min were < 0.010, < 0.010, 0.018, 0.020, 0.016, and 0.013 mg/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 0.110 mg/L) without clinical effects. Minor adverse events occurred in 49 patients (73%): exclusively transient local erythema; resolving or decreasing within 30 min. Feasibility was excellent (≥ 4/5) in 87% at application and 82% at removal. Conclusion: In this clinical trial including 67 children, the S-Caine patch was safe and feasible for use in patients under three, with plasma lidocaine concentrations well below strict clinically relevant thresholds and adverse events only occurring locally, supporting its role as a non-invasive analgesic for procedural pain. Future studies are needed to confirm safety in larger paediatric populations. Clinical Trial Registration: EU Clinical Trials Register, EudraCT Number 2019–002094-55, https://www.clinicaltrialsregister.eu/ctr-search/trial/2019-002094-55/BE .
Anciaux et al. (Thu,) studied this question.