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Disposition of propoxyphene and propranolol in children
Insights
This study examined propoxyphene and propranolol drug disposition in children. Results showed significant individual differences in drug plasma concentrations, suggesting personalized therapy monitoring is crucial for children.
Area of Science:
- Pharmacokinetics
- Pediatric Pharmacology
Background:
- Limited data exists on propoxyphene and propranolol pharmacokinetics in children.
- Understanding drug disposition in pediatric populations is essential for safe and effective treatment.
Purpose of the Study:
- To investigate the pharmacokinetic disposition of propoxyphene and propranolol in children.
- To compare the bioavailability of different propranolol formulations in pediatric patients.
- To assess interindividual variability in drug plasma concentrations.
Main Methods:
- Two protocols were used to minimize blood sampling in children.
- Propoxyphene and norpropoxyphene plasma levels were measured after oral administration.
- Propranolol bioavailability was compared between tablet and solution formulations using a crossover design.
Main Results:
- Propoxyphene exhibited an average half-life (T 1/2) of 3.5 hours in children.
- No significant differences in propranolol bioavailability were found between tablets and solutions.
- Both drugs demonstrated marked interindividual variability in plasma concentrations.
Conclusions:
- Pediatric drug disposition of propoxyphene and propranolol is characterized by significant interindividual variability.
- Therapeutic drug monitoring is recommended for children due to variable plasma concentrations.
- Weight-adjusted dosing in children serves only as an initial approximation.
Abstract:
The disposition of propoxyphene and propranolol was studied in children by means of two protocols which minimized the number of blood samples taken from each child. Propoxyphene and its metabolite, norpropoxyphene, were measured in two plasma samples obtained from different children at various times after a single oral dose. These data were pooled and a plasma concentration/time curve was obtained which was consistent with an average T 1/2 of 3.5 hr in this population. The bioavailability of tablets and a solution of propranolol was compared with a crossover design by obtaining plasma samples at the end of the dosage interval during chronic oral administration of various doses. No clear differences in the bioavailability of the two formulations could be detected. Both drugs showed marked interindividual differences in plasma concentrations following oral administration. These findings are consistent with the high hepatic extraction ratio and large presystemic (first pass) effect previously described in adults. The large individual variability supports the concept of monitoring plasma levels as an aid to therapy and demonstrates that the use of a weight-adjusted dose in children can be only an approximation for initial treatment.