Background Nalbuphine is a mixed agonist-antagonist opioid analgesic agent frequently used in paediatrics, and licensed for parenteral use only. Intranasal delivery could be a safe, effective and non-invasive alternative, especially in infants in the acute setting. However, pharmacokinetic (PK) data for this route of administration is completely lacking. The aim of this study was to assess PK of nalbuphine in infants 1–3 months after single intravenous (0.05 mg/kg) and intranasal (0.1 mg/kg) application, respectively.

Methods We conducted a prospective, single centre, open-label pharmacokinetic study in infants 1–3 months undergoing sepsis workup in the emergency unit. Included infants received alternating nalbuphine as 0.05 mg/kg intravenous bolus or as 0.1 mg/kg intranasal spray. PK samples were taken at 3 pre-defined time points (15, 30 and max. 240 min post-dose before discharge). Area under the concentration-time curve (AUC_0-Tlast, and AUC_0-infinity for i.v.) was calculated using noncompartmental analysis and was compared between groups using Wilcoxon test. Further parameters derived included maximum concentration (C_max), time of maximum concentration (T_max for i.n.) and terminal half-life (t_1/2).

Results A total of 31 patients were included in the analysis. Median age was 55 days [interquartile range 38–63] in the intranasal (N=20) and 42 [37–76] days in the iv group (N=11). Median AUC_0-Tlast was 7.6 (5.4–10.4) mcg*h/L following intranasal versus 7.9 (6.0–14.7) mcg*h/L for iv administration (p=0.46). AUC_0-Tlast (i.v.) covered 80 [68–83]% of AUC_0-infinity. Median C_max was 4.5 [3.5–5.6] mcg/L (i.n.) versus 6.5 [5.3–15.9] mcg/L (i.v.) (p=0.014), t_1/22.4 [1.3–2.8] h (i.n.) versus 1.3 [1.1–1.5] h (i.v.) (p=0.021). T_max occurred 37 [32–65] min after intranasal administration.

Conclusion This first PK study of intranasal nalbuphine in infants suggests that 0.1 mg/kg i.n. dosing provides similar exposure as 0.05 mg/kg i.v. in infants in terms of AUC, and hence intranasal bioavailability close to 50%.

Disclosure(s) Nothing to disclose