Pharmacokinetics of oxycodone after intravenous, buccal, intramuscular and gastric administration in children.
OBJECTIVE
To evaluate the pharmacokinetics of four administration routes of oxycodone parenteral liquid (10 mg/mL), single intravenous and intramuscular injections and buccal and gastric administration, in children.


METHODS
Forty generally healthy children, aged 6-93 months, undergoing inpatient surgery.


METHODS
After induction of anaesthesia, children received a single dose of oxycodone 0.1 mg/kg intravenously (n = 9), intramuscularly (n = 10), buccally (n = 11) or via an orogastric tube into the stomach (n = 10). Regular blood samples were collected up to 12 hours, and plasma was analysed for oxycodone using gas chromatography-mass spectrometry (limit of quantification 1 microg/L).


RESULTS
The peak drug concentration observed was 57-110 (mean 82) microg/L after intravenous administration, 23-54 (34) microg/L after intramuscular administration, 3.9-14 (9.8) microg/L after buccal administration and 1.7-15 (9.2) microg/L after gastric administration. The time to peak concentration was 2-30 (16) minutes in the intramuscular group, 30-480 (221) minutes in the buccal group and 60-360 (193) minutes in the gastric group. The terminal elimination half-lives were closely similar in the four groups: 124-208 (163) minutes in the intravenous group, 162-227 (150) minutes in the intramuscular group, 73-234 (150) minutes in the buccal group and 80-246 (147) minutes in the gastric group. Area under the concentration-time curve (AUC) was 5037-8954 (6612) microg x min/L in the intravenous group, 3084-5524 (4473) microg x min/L in the intramuscular group, 1444-5560 (3658) microg x min/L in the buccal group and 692-3843 (2436) microg x min/L in the gastric group. The estimated bioavailability (AUC/mean intravenous AUC) of intramuscular oxycodone was 0.47-0.84 (0.68), that of buccal oxycodone 0.22-0.84 (0.55) and that of gastric oxycodone 0.10-0.58 (0.37).


CONCLUSIONS
The pharmacokinetics of intravenous oxycodone in children aged 6-93 months are fairly similar to those reported in adults. Intramuscular administration provides relatively constant drug absorption, but after buccal and gastric administration the interindividual variation in the rate and extent of absorption is large.
Kokki
Hannu
H
Department of Anaesthesiology and Intensive Care, Kuopio University Hospital, Kuopio, Finland. hannu.kokki@kuh.fi
Rasanen
Ilpo
I
Reinikainen
Matti
M
Suhonen
Pekka
P
Vanamo
Kari
K
Ojanperä
Ilkka
I
D000278:Administration, Buccal; D000284:Administration, Oral; D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D001682:Biological Availability; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D007273:Injections, Intramuscular; D007275:Injections, Intravenous; D007441:Intubation, Gastrointestinal; D008297:Male; D010098:Oxycodone / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D010149:Postoperative Pain / Q000188:drug therapy; D011446:Prospective Studies; D013997:Time Factors
D000701:Analgesics, Opioid; D010098:Oxycodone