Propranolol plasma monitoring in children submitted to surgery of tetralogy of Fallot by a micromethod using high performance liquid chromatography

Population Pharmacokinetics and Pharmacodynamics of Oral Propranolol in Pediatric Patients With Infantile Hemangioma

This study aimed to characterize the population pharmacokinetics and exposure-response relationship of propranolol (Hemangiol^® Syrup for Pediatric) in infants with infantile hemangioma. Using nonlinear mixed-effects modeling with 63 pooled sets of plasma concentration-time data from 32 Japanese patients aged 35-150 days, we described the disposition of propranolol adequately by a 1-compartment model with first-order absorption. The estimated population mean apparent clearance and apparent central volume of distribution were 9.34 L/h and 146 L, respectively. Body weight and postnatal age influenced the population pharmacokinetic model. The clinical end points-success (complete or nearly complete resolution of the target hemangioma) and failure-at weeks 12 and 24 were characterized by logistic regression using the area under the concentration-time curve (AUC), estimated from the final population pharmacokinetic model, as an exposure predictor. The logistic regression showed that a higher AUC was associated with a higher probability of successful treatment. At each exposure level, probability of successful treatment was correlated with gestational age and treatment duration. Model-predicted probabilities of successful treatment were consistent with actual results in the clinical trial. Simulations using several dosing regimens indicated that oral propranolol at 3 mg/kg per day was effective and would be appropriate for treating Japanese infants. These simulation results can support optimization of dosing regimens, such as selecting amounts, treatment durations, and dosing intervals, for clinical use.

Propranolol pharmacokinetics in infants treated for Infantile Hemangiomas requiring systemic therapy: Modeling and dosing regimen recommendations

Propranolol has become the first choice therapy for complicated Infantile Hemangiomas (IH). The pharmacokinetics of propranolol were evaluated after repeated oral administration of a new pediatric solution of propranolol at 3 mg kg⁻¹ day⁻¹ given twice daily (BID) in infants (77‐243 days) with IH. A population model was built to describe the pharmacokinetics of propranolol in infants and to simulate different dosing regimens. One hundred and sixty‐seven plasma concentrations from 22 infants were used in the population analysis. Weight effect was tested on apparent clearance and volume of distribution. Monte‐Carlo simulations were performed for 4 dosing regimens: BID dosing with irregular or strict 12‐hour intervals and 2 different 3 time daily dosing (TID) regimens. The best model was a one‐compartment model with first‐order absorption and elimination rates. The weight affected the clearance but not the volume. Typical oral clearance was estimated at 3.06 L hour⁻¹ kg⁻¹ (95% CI: 1.14‐8.61 L hour⁻¹ kg⁻¹), close to adult clearance data. When regular BID dosing was compared to TID or irregular BID regimens, simulated median Cmin and Cmax were <20% different. To conclude, a model using a weight allometric function on clearance was established and confirmed that the dose in mg/kg should be used without adaptation by range of age in treatment of complicated IH. The simulations support the use of a BID dosing preferably to a TID dosing thanks to close Cmin and Cmax at steady state between both regimen and showed the possibility of irregular BID dosing, allowing early administration in the evening when needed.

At what age should tetralogy of Fallot be corrected?

Tetralogy of Fallot can be corrected with very low mortality at any age, even in neonates, but this does not necessarily mean that it should be corrected in the neonatal period. Although there are many advantages to early correction, a high proportion of these neonates have residual stenosis or pulmonary regurgitation that impairs ventricular function and may require further surgery or implantation of a pulmonary valve. Before we had the ability to correct this anomaly with low mortality in small children, a variety of palliative procedures had to be performed. Today, with better understanding of the anatomy of tetralogy of Fallot, we should consider what forms of palliation will increase growth of the right ventricular outflow tract in order to reduce the complications of very early surgery.