C H A P T E R 4 3
Drugs affecting blood pressure
675
O
ther antihypertensive agents
Diuretic agents
Diuretics are drugs that increase the excretion of sodium
and water from the kidney (Figure 43.3). See Chapter
51 for a detailed discussion of these agents. Diuretics
are very important for the treatment of hypertension.
These drugs are often the first agents tried in mild
hypertension; they affect blood sodium levels and blood
volume. A somewhat controversial study, the Anti
hypertensive and Lipid-Lowering Treatment to Prevent
Heart Attack Trial (ALLHAT), reported in 2002 that
people taking the less expensive, less toxic diuretics
did better and had better blood pressure control than
people using other antihypertensive agents. Replica-
tions of this study have supported its findings and the
use of a thiazide diuretic as the first drug used in the
management of hypertension. Although these drugs
increase urination and can disturb electrolyte and
acid–base balances, they are usually tolerated well by
most people. Diuretic agents used to treat hypertension
include the following:
•
Thiazide and thiazide-like diuretics
:
hydrochlorothiazide (
Dithiazide
),
chlorthalidone
(
Hygroton
) and indapamide (
Dapa-Tabs
).
•
Potassium-sparing diuretics
: amiloride (
Amizide,
Kaluril
), spironolactone (
Aldactone, Spiractin
) and
triamterene (
Hydrene
).
Sympathetic nervous system blockers
Drugs that block the effects of the sympathetic nervous
system are useful in blocking many of the compen-
satory effects of the sympathetic nervous system (see
Figure 43.3). See Chapters 30 and 31 for a detailed dis-
cussion of these drugs.
• Beta-blockers block vasoconstriction, decrease heart
rate, decrease cardiac muscle contraction and tend
to increase blood flow to the kidneys, leading to a
decrease in the release of renin. These drugs have
many adverse effects and are not recommended for
all people. They are often used as monotherapy,
and in some people they control blood pressure
adequately. Beta-blockers used to treat hypertension
include the following agents: atenolol (
Tenormin
),
betaxolol (
Betoquin
), metoprolol (
Betaloc
,
of the drug
: any known allergies to these drugs;
impaired kidney or liver function; pregnancy or
breastfeeding
because of the potential adverse
effects on the fetus or neonate
;
and cardiovascular
dysfunction,
which could be exacerbated by a fall
in blood pressure.
■
■
Assess baseline status before beginning therapy
to determine any potential adverse effects
;
this
includes body temperature and weight; skin colour,
lesions and temperature; pulse, blood pressure,
baseline ECG and perfusion; respirations and
adventitious breath sounds; bowel sounds and
abdominal examination; renal and liver function
tests; and blood glucose.
Implementation with rationale
■
■
Encourage the person to implement lifestyle
changes, including weight loss, smoking cessation,
decreased alcohol and salt in the diet and
increased exercise,
to increase the effectiveness of
antihypertensive therapy.
■
■
Monitor blood pressure closely during
administration
to evaluate for effectiveness and
to ensure quick response if blood pressure falls
rapidly or too much.
■
■
Monitor blood glucose and serum electrolytes
to avoid potentially serious adverse effects.
■
■
Monitor the person carefully in any situation that
might lead to a drop in fluid volume (e.g. excessive
sweating, vomiting, diarrhoea, dehydration)
to
detect and treat excessive hypotension that may
occur.
■
■
Provide comfort measures
to help the person
tolerate drug effects
, including small, frequent
meals; access to bathroom facilities; safety
precautions if CNS effects occur; environmental
controls; appropriate skin care as needed; and
analgesics as needed.
■
■
Provide thorough teaching, including the name
of the drug, dosage prescribed, measures to avoid
adverse effects, warning signs of problems and
the need for periodic monitoring and evaluation,
to enhance knowledge about drug therapy and to
promote compliance.
■
■
Offer support and encouragement
to help the
person deal with the diagnosis and the drug
regimen.
Evaluation
■
■
Monitor response to the drug (maintenance of
blood pressure within normal limits).
■
■
Monitor for adverse effects (hypotension, GI
distress, skin reactions, tachycardia, headache,
dizziness).
■
■
Evaluate the effectiveness of the teaching plan
(person can name drug, dosage, adverse effects to
watch for, specific measures to avoid them and the
importance of continued follow-up).
■
■
Monitor the effectiveness of comfort measures and
compliance with the regimen.
