General Principals (Class)
Beta adrenergic blocking agents prevent stimulation of the beta adrenergic receptors at the nerve endings of the sympathetic nervous system and therefore decrease the activity of the heart. They block sympathetic stimulation of the heart and reduce systolic pressure, heart rate, cardiac contractility and output, so decrease myocardial oxygen demand and increase exercise tolerance (agents, 2013)
Indications
Adrenergic blocking agents are used to treat angina, control abnormal heart rhythms and to reduce high blood pressure (agents, 2013). They are also used to treat a variety of other conditions including benign prostatic hyperplasia and Reynaud’s disease (Blockers, 2013).
Cautions
Adrenergic blocking drugs are typically not used on people with asthma because they may trigger severe asthma attacks. Also with people who have diabetes, adrenergic blocking drugs may block signs of low blood sugar, such as rapid heartbeat (Blockers, 2013).
Mechanism of Action
To interrupt the stimulation of the SNS at the alpha 1- adrenergic receptors.
Alpha blockers work to bind and antagonize receptors by blocking norepinephrine making it non responsive called a competitive blockade.
A covalent bond makes receptors less responsive but responsive in a small amount to norepinephrine called a noncompetitive blockade.
Adverse Effects
Sudden drop in blood pressure after the first dose called the first-dose phenomenon, causing the patient to pass out.
Cardiovascular palpitations, tachycardia, edema and angina.
Nausea and vomiting, diarrhea, constipation, dry mouth and abdominal
Toxic Effects
In the case of an overdose, activated charcoal is the standard choice of med because after administered it binds to the drug and is removes it from the stomach and the circulation.
Supportive measures include vitals, fluids, and anticonvulsants such as diazepam for the control of seizures.
Route of Administration
Alpha1 Blockers
Mostly administered orally(PO)
Except for phentolamine, administration routes are intravenous(IV), intramuscular(IM), and subcutaneously(subcut)
Phentolamine can be used for extravasation of vasoconstricting drugs(e.g., norepinephrine, epinephrine, and dopamine) subcutaneously(subcut) in a circular fashion around the extravasation site to increase blood flow to the ischemic tissue and thus prevent permanent damage.
Beta Blockers Nonselective
Mostly administered PO
Labetalol(Normodyne, Trandate) and propranolol(Inderal) are administered PO and IV
Timolol PO, IV, and ophthalmic for glaucoma (Skidmore-Roth, 2013)
Cardioselective
Mostly administered PO
Metoprolol (Lopressor, Toprol-XL), PO and IV
Esmolol (Brevbloc) IV only (Lilly Lane, Rainforth Collins, & Snyder, 2014)
Common Drug Interactions
Antacids (aluminum hydroxide type)
Decrease absorption resulting in decreased beta blocker activity
Antimuscarinics and Anticholinergics
Antagonism resulting in reduction of beta blocker effects
Digoxin
Additive effect, enhancing bradycardic effects of digoxin
Diuretics, cardiovascular drugs, alcohol
Additive effect resulting with additive hypotensive effects
Neuromuscular blocking drugs
Additive effect by prolonging neuromuscular blockade
Oral hypoglycemic drugs and Insulin
Mask signs of hypoglycemia and delay recovery from hypoglycemia (Lilly Lane, Rainforth Collins, & Snyder, 2014)
Nursing implications for patients taking Adrenergic Blocking Drugs include:
Patient teaching (Lilly, Collins, Synder, 2014, Pg 319-322)
Wear a medical alert bracelet or necklace
Carrying around a list of medications and specific diagnosis around with them at all times
Take medication exactly as prescribed and never to stop the medication abruptly
Avoid caffeine and other CNS stimulants
Avoid consuming any alcohol
Contact your doctor immediately if and when you experience any of the following: Palpitations, chest pain, confusion, weight gain of 2
