Pharmacokinetics of ketoprofen following oral and intramuscular administration in young children

Objective: The pharmacokinetics of ketoprofen following intramuscular injection or oral tablet was determined in children aged 10–69 months. Methods: Ten children received a single intramuscular injection of 1 mg kg–1 ketoprofen. Six children, weight 12–17 kg, received a 12.5-mg ketoprofen tablet and four children, weight 18–23 kg, received a 25-mg tablet. Venous blood samples were collected at 15 min and 30 min and 1, 2, 4, 6 and 8 h following drug dosing. Plasma ketoprofen levels were measured using a validated high-performance liquid chromatography method. Results: The maximal plasma concentration of ketoprofen ranged between 3.6 µg ml–1 and 7.4 µg ml–1 in the intramuscular group and, following a dose normalisation, between 2.8 µg ml–1 and 8.2 µg ml–1 in the tablet group (dose normalised for 1 mg kg–1). The rate and extent of absorption of ketoprofen were comparable after intramuscular and oral administration. The relative bioavailability of oral ketoprofen was about 100% of the intramuscular administration. The extrapolated area under the plasma concentration–time curve (AUC0– ∞) ranged between 8.8 µg ml–1 h and 14.6 µg ml–1 h in the intramuscular group and between 8.7 µg ml–1 h and 14.1 µg ml–1 h in the tablet group (dose-normalised AUC0– ∞). The terminal half-life was comparable in both study groups, ranging between 0.8 h and 2.2 h in the intramuscular group and between 0.9 h and 2.1 h in the tablet group. Conclusion: According to the pharmacokinetic properties determined in this study, there is no justification for using intramuscular administration in awake children.