58
P A R T 1
Introduction to nursing pharmacology
paediatric doses. This is a good practice when working
with small children.
Body surface area
The surface area of a child’s body may also be used to
determine the approximate dose that should be used.
To do this, the child’s surface area is determined with
the use of a nomogram (Figure 5.1). The height and
weight of the child are taken into consideration in this
chart. The following formula is then used:
child’s dose =
surface area (m
2
)
1.73
×
average adult dose
This method is more precise than the formula
methods, but you have to have a nomogram available to
determine the surface area.
Milligrams/kilograms of body weight
When a safe and effective paediatric dose has been estab-
lished, the orders for the drug dose are often written in
milligrams/kilograms. This method of prescribing takes
into consideration the varying weights of children and
the need for a higher dose of the drug when the weight
increases. For example, if a child with postoperative
nausea is to be treated with ondansetron the recom-
mended dose is 0.1 mg/kg by intravenous injection. If
the child weighs 22 kg, the dose for this child would be
0.1 mg/kg
×
22 kg, or 2.2 mg. If a child weighed only
8 kg, the recommended dose would be 0.1 mg/kg
×
8 kg,
or 0.8 mg. Note that this is only the dosage for the drug.
Before administration, the volume required still needs
to be calculated. The established guidelines allow the
drug to be used safely within a large range of children.
Some adult doses will also be written in this way. This
is usually found in drugs with a small margin of safety
or high potential for toxic effects, such as antineoplastic
drugs.
CHAPTER SUMMARY
■■
The metric system is the most widely used system of
measure. All drugs are dispensed in quantities defined
using the metric system.
■■
Children require doses of most drugs different to
those of adults due to the way their bodies handle
drugs and the way that drugs affect their tissues and
organs.
■■
Paediatric doses are based on body surface area,
which requires the use of a nomogram, and
milligrams per kilogram of body weight.
Knowing your strengths and weaknesses helps you to
study more effectively. Take a PrepU Practice Quiz
to find out how you measure up!
ONLINE RESOURCES
An extensive range of additional resources to enhance teaching
and learning and to facilitate understanding of this chapter may
be found online at the text’s accompanying website, located on
thePoint at
These include Watch and
Learn videos, Concepts in Action animations, journal articles,
review questions, case studies, discussion topics and quizzes.
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