672
P A R T 8
Drugs acting on the cardiovascular system
on a calcium channel blocker reports toxic effects, ask
whether they are drinking grapefruit juice and if so
advise them to cease drinking the juice.
Prototype summary: Diltiazem
Indications:
Treatment of essential hypertension in
the extended-release form.
Actions:
Inhibits the movement of calcium ions
across the membranes of cardiac and arterial muscle
cells, depressing the impulse and leading to slowed
conduction, decreased myocardial contractility and
dilation of arterioles, which lowers blood pressure
and decreases myocardial oxygen consumption.
Pharmacokinetics:
Route
Onset
Peak
Duration
Oral, ext
release
30–60 mins 6–11 hours 12 hours
T
1/2
:
5–7 hours; metabolised in the liver and excreted
in urine.
Adverse effects:
Dizziness, light-headedness,
headache, peripheral oedema, bradycardia,
atrioventricular block, flushing, nausea.
Care considerations for
people receiving calcium channel blockers
The main use of calcium channel blockers is for the
treatment of angina. See Chapter 46 for the care
considerations of calcium channel blockers.
See
the Critical thinking scenario for the initiation of
antihypertensive therapy using calcium channel
blockers
.
CRITICAL THINKING SCENARIO
Initiating antihypertensive therapy
THE SITUATION
B.R., a 46-year-old Indigenous Australian male business
executive, was seen for a routine insurance physical. His
examination was normal except for a blood pressure
reading of 164/102 mmHg. He also was approximately
10 kg overweight. Urinalysis and blood work results were all
within normal limits. He was given a 5000-kilojoule-per-day
diet to follow and was encouraged to reduce his salt and
alcohol intake, start exercising and stop smoking. He was
asked to return in 3 weeks for a follow-up appointment.
Three weeks later, B.R. returned with a 3.5 kg weight loss
and an average blood pressure reading (of three readings)
of 145/92 mmHg. Discussion was held about starting B.R. on
a diuretic in addition to the lifestyle changes that B.R. was
undertaking. B.R. was reluctant to take a diuretic and, after
much discussion, was prescribed a calcium channel blocker.
B.R. asked for a couple more weeks to try to bring his
blood pressure down with lifestyle changes before starting
the drug.
CRITICAL THINKING
What care interventions should be done at this point?
Consider the risk factors that B.R. has for hypertension and
the damage that hypertension can cause.
What are the chances that B.R. can bring his blood pressure
within a normal range with lifestyle changes alone?
What additional teaching points should be covered with
B.R. before a treatment decision is made?
What implication does the diagnosis of hypertension have
for B.R.’s insurance and job security?
What effects could diuretic therapy have on B.R.’s busy
business day?
DISCUSSION
B.R. was asked to change many things in his life over the last
3 weeks. These changes themselves can be stressful and can
increase a person’s blood pressure. B.R.’s reluctance to take
a diuretic is understandable for a business executive who
might not want his day interrupted by many bathroom stops.
B.R. should receive a complete teaching program
outlining what is known about hypertension and all of the
risk factors involved with the disease. The good effects of
weight loss, exercise and other lifestyle changes should
be stressed, and B.R. should be praised for his success over
the last 3 weeks.
B.R. may benefit from trying for a couple more weeks
to make lifestyle changes that will help bring his blood
pressure into normal range. He will then feel that he has
some control and input into the situation, and if drug
therapy is needed, he may be more willing to comply with
the prescribed treatment. The diagnosis of hypertension
may be delayed for these 2 weeks while B.R. changes his
lifestyle. Such a diagnosis should be made only after three
