C H A P T E R 4 6
Antianginal agents
725
serious respiratory depression when given with general
anaesthetics or as an adjunct to anaesthesia.
P
otassium channel opener
There is one other drug group used in the treatment of
angina pectoris, namely potassium channel openers
of which one, nicorandil (
Ikorel
), is currently available.
Therapeutic actions and indications
Potassium channel openers promote opening of ATP
dependent potassium channels located in vascular
smooth muscle, where they cause hyperpolarisation.
This effect leads to dilatation of arteries and reduction
in afterload. The effect also leads to vascular smooth
muscle relaxation, enhancing pooling of blood and
reducing preload.
Pharmacokinetics
Nicorandil is rapidly absorbed after oral administration,
mainly through the gastrointestinal system. Peak levels
are achieved in 30–60 minutes. The drug and its metab-
olites are excreted in urine. Effects during pregnancy
and breastfeeding are unknown so the drug is not rec-
ommended during these periods.
Contraindications and cautions
Nicorandil is contraindicated in the presence of allergy
to the drug, nicotinamide or nicotinic acid
to avoid
hypersensitivity reactions
and with pregnancy or breast-
feeding
because of the potential for adverse effects on
the fetus or neonate.
The drug should not be used in individuals with
cardiogenic shock, hypotension or acute myocar-
dial infarction,
which could be exacerbated by the
conduction-slowing effects of the drug.
Adverse effects
The adverse effects associated with nicorandil are
related to their effects on cardiac output and smooth
muscle. CNS effects include dizziness, light-headedness,
headache and fatigue. GI effects can include nausea,
dyspepsia and abdominal pain. Cardiovascular effects
include hypotension, tachycardia, palpitations and vaso-
dilation. Skin effects include flushing and rash.
Clinically important drug–drug interactions
Nicorandil has been found to have few drug-drug inter-
actions. However, caution should be taken when using
the drug concurrently with other drugs that
lower blood
pressure as this effect may be enhanced
. Use of cortico
steroids with nicorandil has been found to
increase risk
of gastrointestinal perforation
.
Care considerations for people receiving
calcium channel blockers and potassium
channel openers
Assessment: History and examination
■
■
Assess for contraindications or cautions:
known allergies to any of these drugs
to avoid
hypersensitivity reactions
; impaired liver or kidney
function,
which could alter the metabolism and
excretion of the drug
; heart block,
which could
be exacerbated by the conduction depression of
these drugs
; and current status of pregnancy or
breastfeeding
because of the risk of adverse effects
to the fetus or breastfeeding baby.
■
■
Perform a physical assessment to establish baseline
status before beginning therapy and during therapy
to determine the effectiveness and evaluate for any
potential adverse effects.
■
■
Inspect skin for colour and integrity
to identify
possible adverse skin reactions.
■
■
Assess the person’s complaint of pain, including
onset, duration, intensity and location, and
measures used to relieve the pain. Investigate
activity level prior to and after the onset of
pain
to aid in identifying possible contributing
factors to the pain and its progression.
■
■
Assess cardiopulmonary status closely, including
pulse rate, blood pressure, heart rate and rhythm,
to determine the effects of therapy and identify
any adverse effects.
■
■
Obtain an ECG as ordered
to evaluate heart rate
and rhythm.
■
■
Monitor respirations and auscultate lungs
to
evaluate changes in cardiac output.
■
■
Monitor laboratory test results, including liver
and renal function tests,
to determine the need for
possible dose adjustment.
Implementation with rationale
■
■
Monitor the person’s blood pressure, cardiac
rhythm, and cardiac output closely while the drug
is being titrated or dose is being changed
to ensure
early detection of potentially serious adverse
effects.
■
■
Monitor blood pressure very carefully if the person
is also taking nitrates
because there is an increased
risk of hypotensive episodes.
■
■
If a person is on long-term therapy, periodically
monitor blood pressure and cardiac rhythm while
using these drugs
because of the potential for
adverse cardiovascular effects.
■
■
Provide comfort measures
to help the person
tolerate drug effects.
These include small, frequent
