Individual variations in fentanyl pharmacokinetics and pharmacodynamics in preterm infants

Aim Fentanyl pharmacokinetics and pharmacodynamics are lacking in preterm infants. Our aim was to study these and their relation with a new formulation of fentanyl 5 μg/mL for procedural pain. Methods Preterm infants were given 0.5 (n = 20, median gestational age 26.5; range 23.3–34.1 weeks) and 2 μg/kg (n = 8, 27.4; 25.3–30.7 weeks) fentanyl, respectively, before skin‐breaking procedures or tracheal intubation. Blood samples were collected after ten minutes, two, four, eight and 24 hours. Physiologic parameters were monitored and pain scores assessed. Results The median fentanyl concentrations were 0.18, 0.15, 0.15 and 0.57, 0.37, 0.35 ng/mL at 15–31 minutes, two and four hours and the half‐lives were 1.6 to 20.5 or 4.1 to 32.6 hours for the low‐ and high‐dose groups, respectively. A significant correlation was seen between weight at study inclusion and half‐life (Spearman′s r = −0.9, p