Beta Blockers (Sympatholytic Drugs) Flashcards
What is the prototype beta blocker?
Propranolol
What is properties of Propranolol?
Nonselective, pure β1-β2 antagonist activity
What is the effects of beta 1 blockade of Propranolol?
β1 decreases HR and contractility (decreased CO which can lead to Na+ retention)
What is true about the chronotropic vs the inotropic effects of Propranolol?
Chronotropic effects longer than inotropic
What effect is B2 blockade with Propranolol?
β2 increase PVR (coronary vascular resistance)
What is the net effect of Propranolol?
may relieve myocardial ischemia
What is the target goal HR of Propranolol?
Dosed to a clinical goal of HR 55-60
What has replaced Propranolol in anesthesia?
Been replaced mostly by esmolol for anesthesia purposes
What is impacts Propranolol?
Significant hepatic first pass effect
What is the protein binding of Propranolol?
protein binding (90-95%)
What affect does heparin have with Propranolol?
Heparin increases plasma concentration
What affects the pharmokinetics of Propranolol?
Affected by changes in hepatic blood flow and enzyme activity
What is true about plasma concentration of Propranolol?
Plasma concentration does not reflect therapeutic effects
What is the clearance of Propranolol?
- Hepatic clearance with active metabolite: 4-hydroxypropranolol
- More of issue after oral dose
What impact does Propranolol have with local anesthetics?
- Decreases clearance of amide local anesthetics
- Mainly as a result of propranolol-induced decreases in metabolism
What local anesthetic has the biggest impact of Propranolol?
Bupivacaine up to 35% decrease in clearance
What increases the bioavailability of Propranolol?
Decreased pulmonary first pass uptake of fentanyl in patients tx chronically w/propranolol; thus increasing bioavailability 2-4x
What is Nadolol?
long acting nonselective β-blocker (once a day administration)
What is the elimination of Nadolol with renal failure?
increased elimination in renal failure
What is Timolol? What is important to know about this medication?
used as eye drops for glaucoma that can have systemic effects that can be resistant to atropine
What is Metoprolol?
Selective β-1 adrenergic blocker
What is true about the safety profile of Metoprolol?
Less adverse effects for obstructive airway disease, PVD, hypoglycemics
What is the purpose of Metoprolol with anesthesia?
Anesthesia: for controlling heart rate without affecting B/P
What are the clinical effects of Metoprolol?
- Bronchodilation, vasodilation, and metabolic effect of β-2 intact
- Dose related, problematic at larger doses but more easily reversible with β-2 agonists such as terbutaline
What is the dose of Metoprolol?
1- 15 mg IV (2.5- 5 mg q 5 min to 15 mg total or desired effect)
When does Metoprolol peak?
Peaks in approximately 10 min
What is the elimination half time of Metoprolol?
3-4 hours
What is the volume of distribution of Metoprolol?
High Vd (5-6 L/kg)