C H A P T E R 4 6
Antianginal agents
717
and calcium channel blockers are used to treat angina
(Figure 46.2).
All antianginal agents are effective and may be used
in combination to achieve good pain control. The type
of drug that is best for a person is determined by toler-
ance of adverse effects and response to the drug. The use
of antianginal agents with different age groups is dis-
cussed in Box 46.1.
N
itrates
Nitrates
are drugs that act directly on smooth muscle to
cause relaxation and to depress muscle tone. Because the
action is direct, these drugs do not influence any nerve
or other activity and the response is usually quite fast.
Nitrates include isosorbide dinitrate (
Isordil
,
Sorbidin
),
isosorbide mononitrate (
Duride
,
Imdur
and others) and
glyceryl trinitrate (
Anginine
,
Nitro-Dur
,
Nitrolingual
and others).
Therapeutic actions and indications
The nitrates relax and dilate veins, arteries and capillar-
ies, allowing increased blood flow through the vessels
and lowering systemic blood pressure because of a drop
in resistance. Because CAD causes a stiffening and lack
of responsiveness in the coronary arteries, the nitrates
probably have very little effect on increasing blood flow
through these arteries. However, they do increase blood
flow through healthy coronary arteries. Therefore, the
blood supply through any healthy vessels in the heart
increases, possibly helping the heart to compensate
somewhat.
The main effect of nitrates, however, seems to be
related to the drop in blood pressure that occurs. The
Beta-blockers, calcium
channel blockers
Beta-blockers, nitrates,
calcium channel blockers
Beta-blockers, nitrates,
calcium channel blockers
Beta-blockers, calcium
channel blockers
↑
Heart rate
↑
Blood volume (preload)
↑
Blood pressure (afterload)
↑
Left ventricular muscle size
↑
Muscle contractility
↑
Myocardial oxygen consumption
FIGURE 46.2
Interaction of antianginal agents with factors affecting
myocardial oxygen demand.
BOX 46.1
Drug therapy across the lifespan
Antianginal agents
CHILDREN
The antianginals are not indicated for any condition
commonly found in children. In some situations,
particularly congenital heart defects or cardiac surgery,
glyceryl trinitrate may be used.The dose of the drug
should be determined by considering age and weight.
The child should be very carefully monitored for adverse
reactions, including potentially dangerous changes in
blood pressure.
ADULTS
Adults who receive these drugs should be instructed in
their proper administration, particularly if varying forms
of glyceryl trinitrate are used. Individuals should also be
encouraged to determine what activities or situations
tend to precipitate an anginal attack so that they can
take measures to avoid those circumstances or take an
antianginal agent before the event occurs.
With glyceryl trinitrate use, it is important that the
person knows how to use the drug, how to store the drug,
how to determine whether it is still effective and how
much to take before seeking emergency medical care.
People should know that regular medical follow-
up is important and should be instructed in non-
pharmacological measures—weight loss, smoking
cessation, activity changes, diet changes—that could
decrease their risk of coronary artery disease and improve
the effectiveness of the antianginal therapy.
PREGNANCY AND BREASTFEEDING
The safety for the use of these drugs during pregnancy
has not been established.There is a significant potential
for adverse effects on the fetus related to blood flow
changes and direct drug effects when the drugs cross the
placenta.The drugs do enter breast milk, and it is advised
that another method of feeding the baby be used if one of
these drugs is prescribed during breastfeeding.
OLDER ADULTS
Older adults frequently are prescribed one of these
drugs. Older adults are more likely to develop adverse
effects associated with the use of these drugs—
arrhythmias, hypotension and heart disease. Safety
measures may be needed if these effects occur and
interfere with the person’s mobility and balance.
Older adults are also more likely to have renal
and/or hepatic impairment related to underlying medical
conditions, which could interfere with the metabolism
and excretion of these drugs.The dose for older adults
should be started at a lower level than that recommended
for younger adults.The person should be monitored very
closely and dose adjusted based on response.
If other drugs are added to or removed from the drug
regimen, appropriate dose adjustments may need to be
made. If the person is using a different form of glyceryl
trinitrate, special care should be taken to make sure that
the proper administration, storage and timing of use are
understood.
