Adrenergic blocking agents: Lect 8 Flashcards
what is the short term effect of beta blockers on blood pressure
- negative inotropic and chronotropic effect which slows the heart and decreases contractility
- relaxation of skeletal muscle vasculature: B2 receptor blocked
- decreased CO increases sympathetic input -> an initial rise in peripheral resistance due to blockade of β2 receptors in blood vessels, allowing the effect of α receptors to become dominant
what is the long term effect of beta blockers on blood pressure
There may be an initial rise in peripheral resistance due to blockade of β2 receptors in blood vessels, allowing the effect of α receptors to become dominant. Over time, however, peripheral resistance returns to normal and blood pressure goes down
Effects of beta blockers on respiration
- causes Bronchoconstriction
Beta blockers will inhibit the vasodilation caused by β2 receptors, increasing the pressor effect of epinephrine. They should never be given to someone with pheochromocytoma without administering what drugs
concomminant administration of an alpha blocker!
why should beta-blockers not be given in people who have asthma/COPD
Beta-blockers causes bronchoconstriction and can be fatal!
- beta1 selective drug might be tolerated
function of beta-blockers in the eye
- lowers intraocular pressure
- decreases formation of aqueous humor
why should beta blockers be used with great caution in insulin dependent Type I diabetics
- Glycogenolysis mobilizes glucose in response to hypoglycemia. This effect is decreased by β antagonists
- In normal patients, when glycogenolysis and gluconeogenesis are inhibited, release of glucagon in response to hypoglycemia acts to increase the blood glucose
- in type I diabetics, the glucagon response becomes impaired, and inhibition of glycogenolysis and decreased release of glucose from the liver due to beta blockade may impair the ability of diabetics to recover from hypoglycemia
- Furthermore, beta antagonists will mask the normal symptoms of hypoglycemia, such as tremor and shakiness.
Beta blockers have what effect on lipolysis, VLDL, and HDL?
- inhibts lipolysis in fat cells (beta 3)
- increases VLDL and decreases HDL
Beta blockers with local anesthetic activity (acebutolol, labetalol, metoprolol, pindolol, propranolol) should not be used in the eye because
- they will anesthetize the cornea
- corneal damage/scratching can occur
MOA of propranolol
- competitive antagonist at B1 and B2 receptors
Propranolol has what CV effects
- Slows heart rate and decreases force of contraction
- Slows conduction through the A-V node
Propranolol has what effect on renin and glycogenolysis
- decreases renin (B1)
- decreases glycogenolysis (B2)
What beta blockers can be used as a local anesthetic
- acebutolol
- labetalol
- metoprolol
- pindolol
- propranolol
pharmacokinetics of Propranolol
- route of administration
- can it enter CNS?
- where is it metabolized
- oral
- lipid soluble, enters CNS -> sedation
- metabolized in the liver, cytochrome P450
clinical uses of propranolol
- treats HTN: not first line agent
- decreases mortality following MI
- improves symptoms of angina: decreases O2 demand
- treat arrhythymias
- improve long-term survival in stable congestive heart failure
- Useful to slow heart and decrease blood pressure in hyperthyroidism
- prevent migraine
- decrease sympathetic symptoms of stage fright
- Decreases catecholamine-induced tremor
Main side effect of beta blockers
- Bronchoconstriction
- do not use in asthmatics or COPD
- Bradycardia
- abrupt discontinuation -> arrhythmias
- exercerbate unstable heart failure
Why should a person not take Cimetidine (Antacid and Antihistamine) and Propranol together
- Cimetidine inhibits cytochrome P450 and will increase effects of propranolol -> bradycardia