Drug dosing in overweight children
Drug dosing basing on the body weight
The weight-based dosage data in PEDeDose are based on total body weight and apply to normal-weight children and their age-dependent body composition. The information in PEDeDose does not implicitly apply to physiological states that have changed in this respect, such as those present in overweight, obesity or ascites.
For example, in the case of an overweight child, the dosages presented and calculated may lead to overdose because the increase in body weight is not linear to the ratio of body composition and other factors relevant to drug dosage.
Depending on the physicochemical properties of an active substance (solubility or distribution in fat/water), the pharmacokinetic parameters can change to varying degrees in the case of overweight and thus negatively influence the duration and/or intensity of the effect. The distribution volume and clearance of the active substance are particularly relevant.
For safe and adequate drug therapy in overweight children, other factors must therefore be taken into consideration when determining the dosage.
Drug dosing in overweight children
The determination of a drug dosage in overweight children is very complex and costly. There is still no consensus on the general approach to dose adjustment.
In addition to "total body weight", various other body masses such as "ideal body weight", "lean body weight" or "adjusted body weight" are suggested for estimating the critical pharmacokinetic parameters. Just like the lipophilic or hydrophilic properties of the active substance, the required dose types - loading dose versus maintenance dose - must also be taken into consideration.
Only little concrete information is available for everyday clinical use. Isolated dosage information for overweight patients can be found in the product information for healthcare professionals. Some pharmacokinetic studies on specific active substances are available in the literature. Initial information or recommendations on how to proceed have been published.
In particular, the position paper of the «Pediatric Pharmacy Advocacy Group» [Matson KL et al, 2017] and the overview of the challenges of drug dosage in overweight children [Xiong Y et al, 2017] are helpful for understanding and approaching dose adjustment in overweight children.
As a conclusion for the empirical dosage of drugs in overweight children, it can be stated that both the body composition, the site of action, the dose type, the physicochemical properties of the drug and its pharmacokinetic parameters must be taken into account.
Further studies are required for evidence-based dosing in overweight children
Representation of the body mass index in PEDeDose
In PEDeDose, the body mass index (BMI) is displayed under "Calculated dose" in the list of individual child data. Prerequisite for the calculation and display of the BMI is the entry of height and weight under "Child data". The BMI serves healthcare professionals as an indicator of any changes in physiological conditions.
Figure: Representation of the body mass index (BMI) in PEDeDose in the tab "Calculated dose".
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