8-5. BETA-ADRENERGIC BLOCKING AGENTS
Beta-adrenergic blocking agents block beta effects--cardiac rate and force of
contraction, vasodilatation in skeletal muscles, hyperglycemia, and bronchodilatation.
Pharmacological action. Propranolol blocks both beta1 and beta2
(2) Indications/uses. Propranolol is used to treat a variety of conditions. Its
uses are listed below:
(a) Antianginal agent. It lessens the heart's need for oxygen because
it slows the heart rate. With a slower heart rate, there is decreased need for oxygen
and the angina pain diminishes.
Suppressant agent (in the treatment of migraine headaches)
(3) Cautions and warnings. Propranolol should not be administered to
patients who have bronchial asthma, cardiogenic shock, or sinus bradycardia. It should
be used in caution with patients who have a history of allergies, diabetes mellitus,
congestive heart failure, and emphysema. It is important to note that the abrupt
withdrawal of this agent with patients who have heart disease (that is, angina) can
cause arrhythmias or myocardial infarction (heart attack). This occurs because the
sympathetic tone is adjusted to the blockage (probably by producing extra amounts of
norepinephrine); thus, when the blockage is withdrawn, the heart cannot tolerate the
extra norepinephrine that is present.
(4) Side effects. Side effects that can be produced by propranolol include
dizziness or lightheadedness, very slow pulse, mental confusion or depression, cold
hands, and numbness of the toes or fingers.
Metoprolol Tartrate (Lopressor).
Pharmacological actions. Metoprolol is a somewhat selective beta1
Indication. Metoprolol is used as an antihypertensive agent.
(3) Side effects. Side effects associated with this agent include dizziness or
drowsiness, mental depression, and hallucinations.