adrenergic antagonists: beta blockers

Question 1

how do they help heart failure?

Answer 1

• prevent increase in HR and contractility = protects failing heart
• can reduce incidence of arrhythmias (more prone in failing hearts)
• patients with failing hearts have chronic sympathetic stimulation (heart can’t supply enough oxygen, so there’s an attempt to increase CO) – beta blockers reduce the effects

Question 2

how do they help with arrhythmias?

Answer 2

beta receptors control activity at nodes and conduction system – so beta blockers can modulate pacemaker activity

Question 3

how do they help with angina?

Answer 3

• angina is caused by insufficient oxygen supply to the heart
• beta blockers decrease cardiac work = decreases oxygen demand of cardiac tissue

Question 4

propanolol

- adverse effect

Answer 4

• used for anxiety & stage fright (because it blocks symptoms associated with sympathetic activity)
• alcohol withdrawal
• prevents migraines (because it’s lipid soluble and can enter CNS)
• adverse effect: may cause bronchospasm in patients with asthma (because of blocking beta2)

Question 5

what drug is similar to propanolol?

Answer 5

nadolol

Question 6

blocking beta2 receptors can cause what effects to the airways?

Answer 6

bronchospasm in patients with asthma

Question 7

timolol

Answer 7

• ocular hypotensive effects (glaucoma treatment) – decreases aqueous humor secretion from ciliary epithelium
• may be absorbed systemically = adverse effects in patients with asthma or heart failure

Question 8

atenolol

Answer 8

• beta1 selective
• hypertension, angina
• hydrophilic = no CNS penetration; prophylactic for migraines

Question 9

metoprolol

Answer 9

• beta1 selective
• inverse agonist – blocks binding of NE and reduces constitutive activity of beta1
• lowers mortality for patients who’ve had a heart attack or with severe heart failure

Question 10

esmolol

Answer 10

• ester that’s rapidly hydrolyzed

- used in urgent settings (ex: during surgery)

Question 11

what are third generation beta blockers?

Answer 11

have additional actions/mechanisms (ex: vasodilation)

Question 12

labetalol

Answer 12

• third generation
• decreases BP without huge effects on HR and CO
• blocks beta1 and beta2 = decreases BP; also blocks reflex symp. stimulation of heart – block of NE re-uptake
• blocks alpha1 = decreases BP and vasodilation
• stimulates beta2 = vasodilation

Question 13

carvedilol

Answer 13

• third generation
• blocks beta1, beta2, alpha1
• antioxidant and anti-inflammatory effects

Question 14

nebivolol

Answer 14

• third generation
• mixture of enantiomers: one enatiomer is beta1 blocker (leads to a decrease in BP) – other enatiomer increases NO synthase = increases [NO] = vasodilation

Question 15

butoxamine

Answer 15

• beta2 selective

- no obvious clinical application