Pharmacology Demystified

CHAPTER 5 Medication Administration 85
liver function. For example, newborns have an immature liver while the elderly
have decreased liver function.
• Excretion
The kidney is the main organ that excretes medication although some medication
is excreted in bile, feces, respiration, saliva, and sweat. The patient is unable
to excrete drugs if these routes are not functioning properly. The nurse should be
aware of the route in which the drug is excreted from the body and then determine
if that route is fully functional before administering the medication to the patient.
In addition to the pharmacologic response of the drug, the nurse must also
assess other aspects of the patient and the medication. These are:
° Age
The very young and the elderly are more sensitive to drugs than the
average adult because there is a decrease in gastric secretion resulting in
poor absorption through the GI tract. The elderly are particularly sensitive
to barbiturates and central nervous system depressants. Therefore, it is critical
that the nurse assess the patient’s age before administering medication
and carefully monitor very young and elderly patients afterwards for
adverse side effects.
° Body Weight
The prescriber might order medication given at the recommended dose.
However, the recommended dose is typically for a patient whose body
weight is within the average range (70 kg for an adult). The medication might
have a different effect if the patient’s body weight falls outside this range. For
example, the recommended dose might be too strong for a very thin patient
resulting in a toxic effect. Likewise, the recommended dose might be too low
for an obese patient and never reach the therapeutic level. This is particularly
important to assess when administering medications such as antineoplastics
(anti-cancer drugs) where a low therapeutic level can have a non-therapeutic
effect for the patient—resulting in an undesirable outcome. Using body
weight to determine drug dose will avoid this problem.
° Pharmacogenetic
Genetic factors might have a serious influence on the response to a
drug. Depending on the medication, a patient might have a genetically
based adverse reaction to the drug. Therefore, in assessing the patient, the
nurse must determine if parents, siblings, or other close relatives have had
an adverse reaction to the medication.