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P A R T 5
Drugs acting on the autonomic nervous system
Contraindications and cautions
Isoprenaline is contraindicated in the presence of
allergy to the drug or any components of the drug
to
avert hypersensitivity reactions
; with pulmonary hyper-
tension,
which could be exacerbated by the effects
of the drug
; during anaesthesia with halogenated
hydrocarbons,
which sensitise the myocardium to cat-
echolamines and could cause a severe reaction
; with
eclampsia, uterine haemorrhage and intrauterine death,
which could be complicated by uterine relaxation or
increased blood pressure
; and during pregnancy and
breastfeeding
because of potential effects on the fetus or
neonate.
Caution should be used with diabetes, thyroid
disease, vasomotor problems, degenerative heart disease
or history of stroke,
all of which could be exacerbated
by the sympathomimetic effects of the drug
and with
severe renal impairment,
which could alter the excretion
of the drug.
Adverse effects
People receiving isoprenaline often experience adverse
effects related to the stimulation of sympathetic adrener-
gic receptors. CNS effects include restlessness, anxiety,
fear, tremor, fatigue and headache. Cardiovascular
effects can include tachycardia, angina, myocardial
infarction and palpitations. Pulmonary effects can be
severe, ranging from difficulty breathing, coughing and
bronchospasm to severe pulmonary oedema. GI upset,
nausea, vomiting and anorexia can occur as a result of
the slowing of the GI tract with SNS stimulation. Other
anticipated effects can include sweating, pupil dilation,
rash and muscle cramps.
Clinically important drug–drug interactions
Increased sympathomimetic effects can be expected if
this drug is taken with other sympathomimetic drugs.
Decreased therapeutic effects can occur if this drug is
combined with
b
-adrenergic blockers.
Prototype summary: Isoprenaline
Indications:
Management of bronchospasm during
anaesthesia; vasopressor during shock; adjunct in
the management of cardiac standstill and arrest, as
well as serious ventricular arrhythmias that require
increased inotropic action.
Actions:
Acts on beta-adrenergic receptors to
produce increased heart rate, positive inotropic
effect, bronchodilation and vasodilation.
Pharmacokinetics:
Route
Onset
Duration
IV
Immediate
1–2 mins
T
1/2
:
Unknown; metabolised in the tissues.
Adverse effects:
Restlessness, apprehension, anxiety,
fear, cardiac arrhythmias, tachycardia, nausea,
vomiting, heartburn, respiratory difficulties,
coughing, pulmonary oedema, sweating, pallor.
Care considerations for people receiving
β
-specific adrenergic agonists
Assessment: History and examination
■
■
Assess for contraindications or cautions: any
known allergies to any drug or any components
of the drug
to avoid possible hypersensitivity
reactions
; pulmonary hypertension, which
could be exacerbated by the effects of the drug
;
anaesthesia with halogenated hydrocarbons,
which
sensitise the myocardium to catecholamines and
could cause severe reaction
; eclampsia, uterine
haemorrhage and intrauterine death,
which
could be complicated by uterine relaxation or
increased blood pressure
; diabetes, thyroid disease,
vasomotor problems, degenerative heart disease or
history of stroke,
all of which could be exacerbated
by the sympathomimetic effects of the drugs
;
severe renal impairment,
which could interfere
with the excretion of the drug
; and current status
of pregnancy and breastfeeding.
■
■
Perform a physical assessment to establish a
baseline before beginning therapy and during
therapy
to determine the drug’s effectiveness and
identify any potential adverse effects.
■
■
Assess cardiovascular status, including pulse
rate and blood pressure,
to evaluate for any
cardiovascular effects associated with SNS
stimulation
; obtain an ECG
to evaluate for
changes indicating excessive SNS stimulation.
■
■
Assess respiratory status and listen for adventitious
sounds
to monitor drug effects and assess for any
adverse effects.
■
■
Monitor urine output
to evaluate renal function
and kidney perfusion.
■
■
Monitor laboratory test results, including thyroid
function tests, blood glucose levels and renal
function,
to monitor drug effects and potential
adverse effects.
Implementation with rationale
■
■
Monitor pulse and blood pressure carefully during
administration
to arrange to discontinue the drug
at any sign of toxicity.
■
■
Ensure that a
β
-adrenergic blocker is readily
available when giving parenteral isoprenaline
in case severe reaction occurs.
