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CONTINUING PROFESSIONAL DEVELOPMENT
COUNSELLING IN PRACTICE
Glyceryl trinitrate for acute
BY ANGUS THOMPSON
Fred Smith is a 66-year-old male who requests a Nitrolingual spray following
a recent diagnosis of angina, after he experienced an attack whilst splitting
and stacking two tons of firewood ready for the winter. Fred has visited your
pharmacy regularly for several years, primarily to collect his antihypertensive
medication; amlodipine tablets 5 mg once daily.
What is angina?
Stable angina is pain or discomfort in
the middle of the chest, which occurs
when blood supply to the cardiac
muscle is insufficient to meet demand.
While chest pain is probably the most
common symptom of angina, it is
important to recognise that not all
people with angina report pain, others
may describe the sensation as pressure
or tightness. Angina pain may radiate,
most commonly to the neck, jaw and
upper arm; but sometimes to the back
or shoulder. Where radiation occurs, it is
most often, but not always to the left
side. In some angina sufferers, there may
be other accompanying symptoms such
as sweating or breathlessness.
In stable angina the imbalance of blood
supply and demand invariably results
primarily from an increased demand,
triggered by increased physical activity,
intense emotion such as excitement or
anger, or occasionally after a large meal.
In contrast unstable angina is part of the
spectrum of acute coronary syndrome
(ACS) that includes myocardial infarction
(MI). This often occurs at rest, tending
to be triggered by a reduction in blood
supply associated with an unstable
atherosclerotic plaque and platelet
aggregation. Further discussion of
unstable angina is outside the scope of
this article, the remainder of which will
focus on stable angina.
What causes angina?
Angina is usually a manifestation of
coronary heart disease (CHD), in which
the development of atherosclerosis
narrows the lumen of one of more
coronary arteries. This leads to an
impediment in blood flow and thereby
a reduced oxygen and nutrient supply
to the cardiac muscle, resulting in
The severity of angina depends
to a large extent on the degree of
atherosclerosis and may be graded
according to the level of activity that
triggers symptoms. People with mild
stable angina may rarely have symptoms
and find these are only triggered by
profound exertion, such as that which
occurred in Fred’s case. In contrast, those
with severe angina may have symptoms
with very minimal exertion or even at
rest, such that it has a profound effect
on their quality of life.
What medicines are used to treat
The treatment of angina attacks relies on
fast-acting nitrates. Whilst other nitrates
can potentially be used, sublingual
glyceryl trinitrate (GTN) in the form of
a spray (400 mcg) or tablet (600 mcg) is
the medicine of choice.
Do these medicines have side
The desired therapeutic effect of
nitrates is dilation of coronary vessels
to increase blood flow and this effect is
inseparable from a wider vasodilatory
effect. The consequence of this is that
adverse effects can be bothersome
for some patients, often manifesting
as dizziness, headache and flushing.
People who are prescribed GTN should
be reassured that the positive effects
to relieve angina symptoms generally
outweigh the negatives from side
Angus Thompson is a Lecturer in Therapeutics and
Pharmacy Practice at the University of Tasmania,
Hobart and a part-time accredited pharmacist
undertaking home medicines reviews (HMRs) in
After reading this article, pharmacists should be
Describe the causes and symptoms of angina
Outline medicines used to prevent and treat
Counsel patients on managing acute angina
Advise on the storage and expiry of glyceryl
trinitrate (GTN) spray and tablets.
Competencies addressed: 1.3, 6.1, 6.2, 7.2, 7.3 .
Accreditation number: CAP160101A
effects. It is also useful to highlight that
adverse effects tend to be transient.
Furthermore, that simple measure such as
sitting down prior to using GTN can help
reduce the severity and possible adverse
consequences of adverse effects, such as
collapse due to vasodilation-mediated
Can I use these with my other
GTN can be used safely with most other
medicines, however there are exceptions.
Most notable amongst these are the
phosphodiesterase 5 (PDE5) inhibitors
such as sildenafil, used for erectile
dysfunction (ED) and pulmonary arterial
hypertension (PAH). The concurrent use
of nitrates with PDE5 inhibitors can lead
to profound hypotension and should be
avoided. It is however relevant to note
that in the case of PDE5 inhibitors for
ED and GTN for acute angina, the use of
these drugs is intermittent and the need
for these may not coincide. In such cases,
it may be reasonable for a man with ED
to be prescribed a PDE5 inhibitor, but
have access to GTN for the management
of an angina attack, unless there is a
history of the latter being precipitated by
Nitrates are also contraindicated with
This guanylate cyclase
stimulator is emerging as an effective
treatment option for PAH, however the
combination with a nitrate again carries a
risk of profound hypotension.
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