C H A P T E R 3 5
Hypothalamic and pituitary agents
533
risk of uterine contractions that would harm the fetus
or breastfeeding
because of the potential for adverse
effects to the fetus or baby.
The drugs should be stopped during acute illnesses
that might lead to fluid and/or electrolyte imbalance,
and caution should be used in individuals who consume
large amounts of fluid
because of the increased risk of
electrolyte dilution and hyponatraemia.
Adverse effects
The adverse effects associated with the use of these
drugs include water intoxication (drowsiness, light-
headedness, headache, coma, convulsions) related to the
shift to water retention and resulting electrolyte imbal
ance; tremor, sweating, vertigo and headache related
to water retention (a “hangover” effect); abdominal
cramps, flatulence, nausea and vomiting related to stimu
lation of GI motility; and local nasal irritation related to
nasal administration. Local reaction at injection sites is
fairly common. Hypersensitivity reactions have also been
reported, ranging from rash to bronchial constriction.
Clinically important drug–drug interactions
There is an increased risk of antidiuretic effects if the
drugs are combined with carbamazepine; use caution if
combinations are used.
■■
Posterior pituitary hormones are produced in the
hypothalamus and stored in the posterior pituitary.
They include oxytocin and antidiuretic hormone
(ADH).
■■
Lack of antidiuretic hormone produces diabetes
insipidus, which is characterised by large amounts of
dilute urine and excessive thirst.
■■
ADH replacement uses an analogue of ADH,
desmopressin, and can be administered parenterally
or intranasally.
■■
Fluid balance needs to be monitored when individuals
are taking desmopressin.
KEY POINTS
Prototype summary: Desmopressin
Indications:
Treatment of neurogenic diabetes
insipidus, haemophilia A.
Actions:
Has pressor and antidiuretic effects;
increases levels of clotting factor VIII.
Pharmacokinetics:
Route Onset
Peak
Duration
Oral
1 hour
60–90 mins 7 hours
IV, SC 30 mins
90–120 mins Varies
Nasal
15–60 mins 1–5 hours
5–21 hours
T
1/2
:
7.8 minutes, then 75.5 minutes (IV); 1.5 to 2.5
hours (oral); 3.3 to 3.5 hours (nasal); metabolised
in the tissues, excretion is unknown.
Adverse effects:
Headache, facial flushing, nausea,
fluid retention, slight increase in blood pressure,
local reaction at injection site, water intoxication at
high doses.
Care considerations for people receiving
drugs affecting posterior pituitary hormones
Assessment: History and examination
■
■
Assess for history of allergy to any ADH
preparation or components
to avoid
hypersensitivity reactions
; vascular diseases;
epilepsy; renal dysfunction; pregnancy; and
breastfeeding,
which could be cautions or
contraindications to use of the drug.
■
■
Assess for skin lesions; orientation, affect and
reflexes; blood pressure and pulse; respiration and
adventitious sounds; abdominal examination; renal
function tests; and serum electrolytes,
to determine
baseline status before beginning therapy and for
any potential adverse effects
.
Implementation with rationale
■
■
Monitor fluid volume
to watch for signs of water
intoxication and fluid excess
; arrange to decrease
dose as needed.
■
■
Monitor individuals with vascular disease for any
sign of exacerbation
to provide for immediate
treatment.
■
■
Monitor condition of nasal passages if given
intranasally
to observe for nasal ulceration, which
can occur and could affect absorption of the drug.
■
■
Provide thorough teaching, including measures to
avoid adverse effects, warning signs of problems,
and the need for regular evaluation, including
blood tests,
to enhance knowledge about drug
therapy and promote compliance.
Evaluation
■
■
Monitor response to the drug (maintenance of fluid
balance).
■
■
Monitor for adverse effects (GI problems, water
intoxication, headache, skin rash).
■
■
Evaluate the effectiveness of the teaching plan
(person can name drug, dosage, adverse effects
to watch for and specific measures to avoid them;
person can demonstrate proper administration of
nasal preparations).
■
■
Monitor the effectiveness of comfort measures and
compliance with the regimen.
