C H A P T E R 3 1
Adrenergic blocking antagonists
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tolerance (individuals often report that their “get up and
go” is gone), hypoglycaemia or hyperglycaemia and liver
changes. If these drugs are stopped abruptly after long-
term use, there is a risk of angina, MI, hypertension and
stroke because the receptor sites become hypersensitive
to catecholamines after being blocked by the drugs.
Clinically important drug–drug interactions
A paradoxical hypertension occurs when beta-blockers
are given with clonidine, and an increased rebound
hypertension with clonidine withdrawal may also occur.
It is best to avoid this combination.
A decreased antihypertensive effect occurs when
beta-blockers are given with non-steroidal anti-
inflammatory drugs (NSAIDs); if this combination
is used, the person should be monitored closely and
dose adjustment should be made to achieve the desired
control of blood pressure.
An initial hypertensive episode followed by brady
cardia may occur if these drugs are given with adrenaline.
Peripheral ischaemia may occur if the beta-blockers are
taken in combination with ergot alkaloids.
When these drugs are given with insulin or other oral
hypoglycaemic agents, there is a potential for change in
blood glucose levels. The person will also not display the
usual signs and symptoms of hypoglycaemia or hyper-
glycaemia, which are caused by activation of the SNS.
Because these effects are blocked, the person will need
new indications to alert them to potential problems.
If this combination is used, the person should monitor
blood glucose levels frequently throughout the day and
should be alert to new manifestations indicating glucose
imbalance.
Prototype summary: Propranolol
Indications:
Treatment of hypertension, angina
pectoris, idiopathic hypertrophic subaortic stenosis
(IHSS), supraventricular tachycardia, tremor;
prevention of reinfarction after MI; adjunctive
therapy in phaeochromocytoma; prophylaxis of
migraine headache; management of situational
anxiety.
Actions:
Competitively blocks beta-adrenergic
receptors in the heart and juxtaglomerular
apparatus; reduces vascular tone in the CNS.
Pharmacokinetics:
Route Onset
Peak
Duration
Oral
20–30 mins 60–90 mins 6–12 hours
IV Immediate 1 min
4–6 hours
T
1/2
:
3 to 5 hours with hepatic metabolism and
excretion in the urine.
Adverse effects:
Allergic reaction, bradycardia, HF,
cardiac arrhythmias, cerebrovascular accident,
pulmonary oedema, gastric pain, flatulence,
impotence, decreased exercise tolerance,
bronchospasm.
Care considerations for people receiving
non-selective beta-adrenergic blocking
agents
Assessment: History and examination
■
■
Assess for contraindications or cautions: known
allergy to any drug or to any components of
the drug
to avoid hypersensitivity reactions
;
bradycardia or heart blocks, shock or HF,
which
could be exacerbated by the cardiac-suppressing
effects of these drugs
; bronchospasm, COPD or
acute asthma,
which could worsen with blocking
of the sympathetic bronchodilation
; diabetes or
hypoglycaemia,
which could lead to altered blood
glucose levels
; thyrotoxicosis
because of adrenergic
blocking effects on the thyroid gland
; renal or
hepatic dysfunction,
which could interfere with the
excretion or metabolism of these drugs
; and status
of pregnancy and breastfeeding
because of the
potential effects on the fetus or neonate.
■
■
Perform a physical assessment to establish baseline
data
for determining the effectiveness of the drug
and the occurrence of any adverse effects.
■
■
Assess level of orientation and sensory function
to
evaluate for possible CNS effects.
■
■
Monitor cardiopulmonary status, including pulse,
blood pressure and respiratory rate; auscultate
lungs for adventitious breath sounds; obtain
an ECG as ordered
to evaluate for changes in
heart rate or rhythm
;
check colour, sensation,
and capillary refill of extremities
to evaluate for
possible peripheral vascular insufficiency.
■
■
Assess abdomen, including auscultating bowel
sounds,
to monitor for GI effects.
■
■
Monitor the results of laboratory tests, such
as electrolyte levels, to
monitor for risk of
arrhythmias
, adrenal and hepatic function
studies,
to determine the need for possible dose
adjustment.
■
■
Refer to the Critical thinking scenario for a full
discussion of care for a person who is receiving
beta-adrenergic blocking agents.
Implementation with rationale
■
■
Do not stop these drugs abruptly after chronic
therapy, but taper gradually over 2 weeks
because
long-term use of these drugs can sensitise the
