Prediction of Antimalarial Drug Clearance in Children: A Comparison of Three Different Interspecies Scaling Methods

Application of Allometric Scaling and Salisbury Rule for the Prediction of Antimalarial Drugs for First-in-Pediatric Dose Selection

BACKGROUND

In pediatric drug development, the selection of first-in-pediatric dose is of immense importance. Generally, the pharmacokinetic information and a safe and efficacious dose of a drug in adults are already known and this information can then be used to select first-in-pediatric dose. The objective of this study was to predict the pediatric dose of antimalarial drugs and compare the predicted dose with the recommended dose.

METHODS

In this study, two simple methods to project a first-in-pediatric dose to initiate a clinical trial for antimalarial drugs were evaluated. These two methods were Salisbury Rule and allometric scaling. The predicted doses of antimalarial drugs by the two methods were compared with the observed doses recommended by the World Health Organization (WHO) or the US Food and Drug Administration (FDA).

RESULTS

In this study, 15 antimalarial drugs with 88 observations (different body weight groups) were evaluated. From allometric scaling, all 88 observations were within 0.5-1.5-fold and 0.7-1.3-fold prediction error. From Salisbury Rule, all 88 observations were within 0.5-1.5-fold and 86 observations were within 0.7-1.3-fold prediction error.

CONCLUSIONS

The proposed methods are simple and quite accurate in their predictive power. These methods can be developed on a spreadsheet or a calculator in a very short period of time and are applicable to first-in-pediatric clinical trials or even in a clinical setting.

First dose in neonates: pharmacokinetic bridging study from juvenile mice to neonates for drugs metabolized by CYP3A

First dose prediction is challenging in neonates. Our objective in this proof-of-concept study was to perform a pharmacokinetic (PK) bridging study from juvenile mice to neonates for drugs metabolized by CYP3A. We selected midazolam and clindamycin as model drugs. We developed juvenile mice population PK models using NONMEM. The PK parameters of these two drugs in juvenile mice were used to bridge PK parameters in neonates using different correction methods. The bridging results were evaluated by the fold-error of 0.5- to 1.5-fold. Simple allometry with and without a correction factor for maximum lifespan potential could be used for a bridging of clearance (CL) and volume of distribution (V_d), respectively, from juvenile mice to neonates. Simulation results demonstrated that for midazolam, 100% of clinical studies for which both the predictive CL and V_d were within 0.5- to 1.5-fold of the observed. For clindamycin, 75% and 100% of clinical studies for which the predictive CL and V_d were within 0.5- to 1.5-fold of the observed. A PK bridging of drugs metabolized by CYP3A is feasible from juvenile mice to neonates. It could be a complement to the ADE and PBPK models to support the first dose in neonates.