Practical pharmacology in paediatric emergencies

Published on 10/02/2015 by admin

Filed under Emergency Medicine

Last modified 22/04/2025

Print this page

rate 1 star rate 2 star rate 3 star rate 4 star rate 5 star
Your rating: none, Average: 0 (0 votes)

This article have been viewed 1122 times

4 Practical pharmacology in paediatric emergencies

Do not skip this chapter! It is not mind-numbing pharmacology and should offer some useful tips on drug dosing in paediatric emergency management. (Please refer to Chapters 5 and 6 for drug dosing tables.)

Methods of estimating drug doses in children

Various methods are used in order to estimate paediatric drug dosages, with each having its own advantages and disadvantages:

1. Age-based dosing regimens:

This method takes into account the differences in physiological development between neonates, infants, children and adolescents. Unfortunately, these differences are not absolute or specific to certain maturational stages of development and do not take into consideration the developmental differences and varied body composition of different children of the same age (fat vs. thin children).

2. Body weight-based dosing regimens:

Although there is a correlation between age and body weight, this does not apply to pharmacokinetics. Children between 2 and 6 years of age can potentially get under-dosed if using a body-weight dosing regimen, as they have an increased clearance of a drug. Attempting to compensate for this increase in clearance by increasing the dosage of the drug may compromise older children who do not have the increased clearance and thus may be potentially overdosed. Therefore a one-size-fits-all approach should not be used for all children.

3. Body surface area-based dosing regimens:

This method works on the premise that the physiology of the child is constant when expressed per unit of body surface area. The difference between the dosages calculated for BSA and body weight is more significant for paediatric patients in the younger age range. Dosing by BSA is more accurate for younger children as, for instance, children aged 2 years may have a dosage calculated by BSA of 1.7 times that calculated by weight. Unfortunately, this method requires complex calculations and may result in overdosing for certain drugs in neonates and infants. It also requires measurement of weight and length, is time-consuming and prone to errors in an emergency setting.

4. Allometric scaling:

This method works on the supposition that drug clearance and volume of distribution are scaled according to a body weight-based formula. It has similar disadvantages to BSA measurements and is inaccurate for children younger than 8 years of age.

There is no evidence to suggest that one or other of these systems is more accurate when determining drug dosages for emergency care. The great majority of drug doses are currently based on body weight, which is also the least complex system, and this is how the doses are presented in this book. As with most issues in pharmacology, it is not quite that simple. There is vigorous debate about what form of weight measurement or calculation should be used for paediatric drug dose calculations.

Dose modification for developmental stage, critical illness and abnormal body composition

Obesity

So what is the bottom line about drug dose modification in emergencies under these special circumstances?