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Plasma concentrations of fentanyl in infants, children and adults
Insights
Infants and children show different plasma fentanyl concentrations compared to adults. These findings suggest infants may tolerate higher fentanyl doses due to these pharmacokinetic differences.
Area of Science:
- Pharmacology
- Anesthesiology
- Pediatrics
Background:
- Fentanyl is a potent opioid analgesic commonly used in anesthesia.
- Age-related differences in drug metabolism and distribution can significantly impact pharmacokinetics.
- Understanding these differences is crucial for safe and effective dosing, especially in pediatric populations.
Purpose of the Study:
- To investigate age-related variations in the plasma concentration-time profile of fentanyl.
- To compare fentanyl pharmacokinetics in infants, children, and adults following intravenous administration.
Main Methods:
- Fentanyl was administered intravenously to three age groups: infants (3-10 months), children (1-9 years), and adults (18-41 years).
- Doses were adjusted based on age: 30 µg/kg for infants and children, 20 µg/kg for adults.
- Plasma fentanyl concentrations were measured using radioimmunoassay for up to 4 hours post-administration.
Main Results:
- Infants exhibited the lowest plasma fentanyl concentrations per microgram per kilogram administered at 4-10 and 60-240 minutes.
- Children had lower plasma concentrations than adults at specific time points (4, 180, and 210 minutes).
- These results indicate significant age-dependent differences in fentanyl's absorption, distribution, or elimination.
Conclusions:
- Infants and children demonstrate distinct plasma fentanyl concentration-time courses compared to adults.
- The observed pharmacokinetic differences support the clinical observation that infants may tolerate larger fentanyl doses.
- Age-specific dosing strategies for fentanyl are warranted to optimize therapeutic outcomes and minimize adverse events.
Abstract:
To evaluate whether there are age-related differences in the plasma concentration-vs-time course of fentanyl, the authors administered fentanyl to seven infants (3-10 months), seven children (1-9 years) and seven adults (18-41 years). Anaesthesia was induced with thiopentone, nitrous oxide, and pancuronium; following tracheal intubation, fentanyl (approximately 30 micrograms X kg-1 for infants and children, 20 micrograms X kg-1 for adults) was administered as a 2-min IV infusion. Anaesthesia was maintained with nitrous oxide, pancuronium, and morphine sulphate as clinically indicated. Plasma samples were obtained for 4 h and fentanyl concentrations determined by radioimmunoassay. Plasma concentrations per microgram X kg-1 fentanyl administered were lowest in infants 4-10 and 60-240 min after the start of the 2-min infusion; values for children were lower than those for adults 4, 180 and 210 min after the start of the 2-min infusion. These findings are consistent with the authors' clinical observation that infants tolerate larger doses of fentanyl than do adults.