482
P A R T 5
Drugs acting on the autonomic nervous system
BETA
1
-SELECTIVE ADRENERGIC BLOCKING
AGENTS
Beta
1
-selective adrenergic blocking agents
(Table 31.5)
have an advantage over the non-selective beta-block-
ers in some cases. Because they do not usually block
beta
2
-receptor sites, they do not block the sympathetic
bronchodilation that is so important for people with
lung diseases or allergic rhinitis. Consequently, these
drugs are preferred for individuals who smoke or who
have asthma, any other obstructive pulmonary disease
or seasonal or allergic rhinitis. These selective beta
blockers are also used for treating hypertension, angina
and some cardiac arrhythmias. Beta
1
-selective adren
ergic blocking agents include atenolol (
Tenormin
),
betaxolol (
Betoptic
), bisoprolol (
Bicor, Bispro
), esmolol
(
Brevibloc
) and metoprolol (
Betaloc, Lopresor
)
.
Therapeutic actions and indications
The therapeutic effects of these drugs are related to
their ability to selectively block beta
1
-receptors in the
SNS at therapeutic doses. As a result, these drugs do not
block the beta
2
-receptors and therefore do not prevent
sympathetic bronchodilation. However, the selectivity is
lost with doses higher than the recommended range.
The blockade of the beta
1
-receptors in the heart and
in the juxtaglomerular apparatus accounts for most of
the therapeutic benefits. Decreased heart rate, contrac-
tility and excitability, as well as a membrane-stabilising
effect, lead to a decrease in arrhythmias, decreased
cardiac workload and decreased oxygen consumption.
The juxtaglomerular cells are not stimulated to release
renin, which further decreases blood pressure. These
drugs are useful in treating cardiac arrhythmias, hyper-
tension and chronic angina and can help to prevent
•
Nausea, diarrhoea
: These gastrointestinal discomforts
often diminish with time. If they become too
uncomfortable or do not improve, talk to your
healthcare provider.
•
Dreams, confusion
: These are drug effects. If they
become too uncomfortable, discuss them with your
healthcare provider.
• Report any of the following to your healthcare provider:
very slow pulse, need to sleep on more pillows at night,
difficulty breathing, swelling in the ankles or fingers,
sudden weight gain, mental confusion or personality
change, fever or rash.
• Avoid over-the-counter medications, including cold and
allergy remedies and diet pills. Many of these preparations
contain drugs that could interfere with this medication.
If you feel that you need one of these, check with your
healthcare provider first.
• Tell any doctor, nurse, or other healthcare provider that
you are taking these drugs, keep all medications out of
the reach of children and do not share these drugs with
other people.
TABLE 31.5
DRUGS IN FOCUS Beta
1
-selective adrenergic blocking agents
Drug name
Dosage/route
Usual indications
atenolol (Tenormin)
Initially 50 mg/day PO, may be increased to
100 mg/day
Treatment of MI, chronic angina,
hypertension in adults (atenolol is more
widely used than the other drugs of this
class for hypertension)
betaxolol (Betoptic)
1–2 drops (gtts) in affected eye(s) for glaucoma
Available as ophthalmic agent for
treatment of ocular hypertension,
open-angle glaucoma
bisoprolol (Bicor, Bispro)
Initially 1.25 mg/day PO for 1 week, increased
weekly to maximum 10 mg/day PO
Treatment of hypertension in adults, alone
or as part of combination therapy
esmolol (Brevibloc)
50–200 mcg/kg per minute IV, with dose
based on person’s response
Treatment of supraventricular tachycardias
(e.g. atrial flutter, atrial fibrillation)
in adults, and non-compensatory
tachycardia when the heart rate must
be slowed (IV use only)
metoprolol (Betaloc,
Lopresor)
50–100 mg PO once daily or b.d. Maximum
400 mg/day
Treatment of hypertension; prevention
of reinfarction after MI; early acute
MI treatment; treatment of stable and
symptomatic HF (extended-release
preparation only)
