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Age-related morphine kinetics in infants
M L Pokela1, K T Olkkola, T Seppälä
1Department of Paediatrics, University of Oulu, Finland.
Insights
Morphine pharmacokinetics in infants show significant age-related changes in clearance and half-life, with wide individual variability. Dosing requires careful, individualized titration to ensure safety and efficacy.
Area of Science:
- Pharmacology
- Neonatal Medicine
- Pediatric Critical Care
Background:
- Morphine is commonly used for pain management in infants.
- Understanding morphine pharmacokinetics is crucial for safe and effective dosing in pediatric populations.
Purpose of the Study:
- To investigate the pharmacokinetics of morphine in infants.
- To determine how postnatal age and critical illness affect morphine clearance and half-life.
Main Methods:
- A single intravenous dose of 0.1 mg/kg morphine was administered to 27 infants.
- Infants were categorized by age: neonates (<1 week), 1 week-2 months, and 2-6 months.
- Pharmacokinetic parameters (clearance, half-life) were analyzed in relation to postnatal age and clinical condition.
Main Results:
- Significant variability in morphine pharmacokinetics was observed, particularly in neonates.
- Morphine half-life decreased and clearance increased significantly with advancing postnatal age.
- Critically ill infants exhibited lower morphine clearance compared to their non-critically ill counterparts.
Conclusions:
- Morphine clearance and half-life in infants approach adult values after one month of age, but individual variability persists.
- Individual titration of morphine dosage is essential to prevent overdosing or underdosing in infants.
- Postnatal age and critical illness are key factors influencing morphine disposition in neonates and infants.
Abstract:
The pharmacokinetics of morphine was studied in 27 infants receiving a single intravenous dose of 0.1 mg/kg morphine after surgery (n = 23) or during mechanical ventilation (n = 4). The pharmacokinetics of morphine varied greatly between the subjects, especially in the neonates. The clearance and half-life varied distinctly with postnatal age. The mean (+/- SD) half-life was 8.1 +/- 8.1 h in 10 neonates younger than 1 week, 5.4 +/- 3.4 h in 10 infants aged from 1 week to 2 months and 2.6 +/- 1.7 h in 7 infants aged from 2 to 6 months. Mean clearance increased significantly with age, being 8.7 +/- 5.8 ml/min/kg in the youngest age group, 11.9 +/- 5.1 ml/min/kg in those aged 1 week to 2 months and 28.0 +/- 8.9 ml/min/kg in those aged 2-6 months, and was also significantly lower in the critically ill infants. The clearance and half-life of morphine begin to approach adult values after the age of 1 month, but great individual variability exists even after that. In order to reduce the risk of overdosing or underdosing, the dose of morphine should be titrated individually.