Beta-adrenergic Receptor Antagonists (Beta Blockers) Flashcards
In general, how do the various Beta Blockers within the class differ?
They differ in liophilicities, metabolic routes, B-receptor selectivities and half lives.
Which of the Beta blockers are more likely to cross the blood-brain barrier?
Those that are more soluble in lipids (more lipophilic)
Describe the differences in Beta receptor selectivity amongst the various Beta blockers?
Whereas propranolol, nadolol, pindolol, and labetalol (Normodyne, Trandate) have essentially equal potency at both the β1- and β2-receptors, metoprolol and atenolol have greater affinity for the β1-receptor than for the β2-receptor.
Compare Beta 1 receptor to Beta 2 receptor location and function?
Beta 1:
- Location: Heart/kidneys
- Functions: Increase HR, increase Lipolysis, increase Myocardial contractility, increase Renin
Beta 2:
- Location: Lungs, blood vessels, GI, bladder, liver, uterus.
- Function: vasodilation, reduced peripheral resistance, bronchodilator, Glycogenolysis, glucagon release, uterine smooth muscle relaxation.
What are some therapeutic indications for Beta blockers?
Anxiety disorders, social phobia, postural tremor, akathisia, aggressive/violent behavior, alcohol withdrawal
What are some relative contraindications to the use of Beta blockers?
The β-receptor antagonists are contraindicated for use in people with asthma, insulin-dependent diabetes, congestive heart failure, significant vascular disease, persistent angina, and hyperthyroidism.
Also, Beta blockers cross the placenta and are excreted in breast milk so use with caution in pregnant/breastfeeding.
Why are Beta blockers relatively contraindicated in insulin-dependent diabetes?
Because the effect of Beta blockers can mask the physical symptoms of hypoglycemia
What are the most common side effects of Beta Blockers? Some less common?
Most Common: Hypotension, bradycardia, and occasionally GI upset.
Depression has been associated but is probably rare. May blunt cognition in some people.
Less common: Insomnia, nightmares, sexual dysfunction, other, vascular issues (Raynaud’s), fatigue, worsening of angina upon discontinuation.
What are some common drug interactions with propranolol?
Concomitant administration of propranolol results in increases in plasma concentrations of antipsychotics, anticonvulsants, theophylline (Theo-Dur, Slo-bid), and levothyroxine (Synthroid).
Barbiturates, phenytoin (Dilantin), and cigarette smoking increase the elimination of β-receptor antagonists that are metabolized by the liver.
Depressed myocardial contractility and AV nodal conduction can occur from concomitant administration of a β-receptor antagonist and calcium channel inhibitors.
Describe the dosage, dosage forms and clinical guidelines for propranolol?
Dosage forms: available in 10-, 20-, 40-, 60-, 80-, and 90-mg tablets; 4-, 8-, and 80-mg/mL solutions; and 60-, 80-, 120-, and 160-mg sustained-release capsules.
For the treatment of chronic disorders, propranolol administration is usually initiated at 10 mg by mouth three times a day or 20 mg by mouth twice daily. The dosage can be raised by 20 to 30 mg a day until a therapeutic effect emerges.
For the treatment of social phobia, primarily the performance type, the patient should take 10 to 40 mg of propranolol 20 to 30 minutes before the performance.
Are there any monitoring requirements while taking propranolol?
Pulse and blood pressure (BP) readings should be taken regularly, and the drug should be withheld if the pulse rate is below 50 beats per minute or the systolic BP is below 90 mm Hg.
Describe how patients should safely discontinue propranolol?
Propranolol should be tapered by 60 mg a day until a dosage of 60 mg a day is reached, after which the drug should be tapered by 10 to 20 mg a day every 3 or 4 days.
