C H A P T E R 3 5
Hypothalamic and pituitary agents
527
Pharmacokinetics
Somatropin is injected and reaches peak levels within
7 hours. Box 35.3 discusses a new delivery system for
this drug. It is widely distributed in the body and local
ises in highly perfused tissues, particularly the liver and
kidney. Excretion occurs through the urine and faeces.
Individuals with liver or renal dysfunction may experi
ence reduced clearance and increased concentrations of
the drug.
Contraindications and cautions
Somatropin is contraindicated with any known allergy
to the drug or ingredients in the drug
to avoid hyper-
sensitivity reactions
. It is also contraindicated in the
presence of closed epiphyses or with underlying cranial
lesions
because of the risk of serious complications
,
and with abdominal surgery and acute illness second
ary to complications of open-heart surgery
because of
potential problems with healing.
It should be used with
caution in pregnancy and breastfeeding
because of the
potential for adverse effects on the fetus
.
Adverse effects
The adverse effects that most often occur when using
GH include the development of antibodies to GH and
subsequent signs of inflammation and autoimmune-type
reactions, such as swelling and joint pain, and the endo
crine reactions of hypothyroidism and insulin resistance.
Clinically important drug–drug interactions
Caution should be used when these agents are combined
with any drugs using the cytochrome P450 liver enzyme
system because of a risk for change in metabolism of the
combined drugs.
Somatropin is a preparation of recombinant DNA–
produced human growth hormone that is used to treat
children with growth failure due to lack of growth
hormone. The drug must be given by injection six
or seven times a week. A new delivery form is now
available to ease the discomfort and trauma of the
frequent injections. The
cool.click
delivery system is a
neon-coloured, needle-free system that delivers the drug
through the skin using a fine mist. Tests have shown a
bioequivalency of this method with standard injection
techniques, and the young people who must use this
drug are much less resistant to the dosing. Various drug
companies anticipate similar delivery systems, which
will provide a therapeutic dose of drugs without the
associated discomfort of intramuscular or subcutaneous
injection.
■■
BOX 35.3
New delivery system for growth
hormone
Prototype summary: Somatropin
Indications:
Long-term treatment of children with
growth failure associated with various deficiencies,
girls with Turner’s syndrome, AIDS wasting and
cachexia, growth hormone deficiency in adults, and
treatment of growth failure in children of small
gestational age who do not achieve catch-up growth
by 2 years of age.
Actions:
Replaces human growth hormone;
stimulates skeletal growth, growth of internal
organs, and protein synthesis.
Pharmacokinetics:
Route
Onset
Peak
IM, SC
Varies
5–7.5 hours
T
1/2
:
15 to 50 minutes; metabolised in the liver and
excreted in the urine and faeces.
Adverse effects:
Development of antibodies to
growth hormone, insulin resistance, swelling, joint
pain, headache, injection-site pain.
Care considerations for people receiving
drugs affecting growth hormone agonists
Assessment: History and examination
■
■
Assess history of allergy to any GH or binder,
presence of closed epiphyses or underlying
cranial lesions, serious infection following
open-heart surgery, abdominal surgery and
pregnancy or breastfeeding status
to determine
contraindications to the use of the drug
.
■
■
Assess height, weight, thyroid function tests,
glucose tolerance tests and GH levels
to determine
baseline status before beginning therapy and for
any potential adverse effects
.
Implementation with rationale
■
■
Reconstitute the drug following manufacturer’s
directions
because individual products vary
;
administer intramuscularly or subcutaneously
for appropriate delivery of drug.
■
■
Monitor response carefully when beginning
therapy
to allow appropriate dose adjustments as
needed.
■
■
Monitor thyroid function, glucose tolerance and
GH levels periodically
to monitor endocrine
changes and to institute treatment as needed.
■
■
Provide thorough teaching, including measures
to take to avoid adverse effects, warning signs
of problems and the need for regular evaluation
(including blood tests)
to enhance knowledge about
