C H A P T E R 3 5
Hypothalamic and pituitary agents
529
disorder (e.g. diabetes, thyroid dysfunction)
that could
be exacerbated by the blocking of GH.
Adverse effects
People with renal dysfunction may accumulate higher
levels of octreotide. GI complaints (e.g. constipation or
diarrhoea, flatulence and nausea) are not uncommon
because of the drug’s effects on the GI tract. Octreo
tide and lanreotide have also been associated with the
development of acute cholecystitis, cholestatic jaundice,
biliary tract obstruction and pancreatitis. People must
be assessed for the possible development of any of
these problems. Other, less common adverse effects
include headache, sinus bradycardia or other cardiac
arrhythmias and decreased glucose tolerance. Because
octreotide and lanreotide are administered subcutane
ously, they can be associated with discomfort and/or
inflammation at injection sites.
Bromocriptine is also associated with GI disturb
ances. Because of its dopamine-blocking effects, it may
cause drowsiness and postural hypotension. It blocks
breastfeeding and should not be used by breastfeeding
women.
Pegvisomant may cause pain and inflammation at
the injection site (common). Increased incidence of infec
tion, nausea and diarrhoea and changes in liver function
may also occur.
Clinically important drug–drug interactions
Increased serum bromocriptine levels and increased
toxicity occur if bromocriptine is combined with eryth
romycin. This combination should be avoided.
The effectiveness of bromocriptine may decrease if it
is combined with phenothiazines. If this combination is
used, the person should be monitored carefully.
People receiving pegvisomant may require higher
doses to receive adequate GH suppression if they are
also taking opioids. The mechanism of action of this
interaction is not understood.
Prototype summary: Bromocriptine mesylate
Indications:
Treatment of Parkinson’s disease,
hyperprolactinaemia associated with pituitary
adenomas, female infertility associated with
hyperprolactinaemia and acromegaly; short-term
treatment of amenorrhoea or galactorrhoea.
Actions:
Acts directly on postsynaptic dopamine
receptors in the brain.
Pharmacokinetics:
Route Onset
Peak
Duration
PO Varies
1–3 hours
14 hours
T
1/2
:
3 hours, then 45 to 50 hours; metabolised in
the liver and excreted in the bile.
Adverse effects:
Dizziness, fatigue, light-headedness,
nasal congestion, drowsiness, nausea, vomiting,
abdominal cramps, constipation, diarrhoea,
headache.
Care considerations for people receiving
growth hormone antagonists
Assessment: History and examination
■
■
Assess for history of allergy to any GH antagonist
or binder
to prevent hypersensitivity reactions
;
other endocrine disturbances,
which could be
exacerbated when blocking GH
; and pregnancy
and breastfeeding
because of the potential for
adverse effects to the fetus and the blocking of
breastfeeding.
■
■
Assess orientation, affect and reflexes; blood
pressure, pulse and orthostatic blood pressure;
abdominal examination; glucose tolerance tests
and GH levels,
to determine baseline status before
beginning therapy and for any potential adverse
effects
.
Implementation with rationale
■
■
Reconstitute octreotide and pegvisomant following
manufacturer’s directions; administer these drugs
subcutaneously and rotate injection sites regularly
to prevent skin breakdown and to ensure proper
delivery of the drug.
■
■
Monitor thyroid function, glucose tolerance and
GH levels periodically
to detect problems and to
institute treatment as needed.
■
■
Arrange for baseline and periodic ultrasound
evaluation of the gallbladder if using octreotide
to detect any gallstone development and to arrange
for appropriate treatment.
■
■
Provide thorough teaching, including measures to
avoid adverse effects, warning signs of problems
and need for regular evaluation (including blood
tests),
to enhance knowledge about drug therapy
and promote compliance.
Instruct a family
member in proper preparation and administration
techniques to ensure that there is another
responsible person to administer the drug if
needed.
Evaluation
■
■
Monitor response to the drug (return of GH levels
to normal, growth and development).
