What do they do?
- Block beta receptors
- norepinephrine and epinephrine can’t bind to beta receptors
- therefore, we won’t elicit a sympathetic nervous system response
What happens during a normal SNS response?
- Increased HR and BP
- Increased strength of heart contractions
- Bronchodilation
- Increase blood glucose via glycogenolisis
Where are beta 1 receptors found?
- Heart
- Kidneys - juxtaglomerolar cells (release renin)
Where are beta 2 receptors found?
- Lungs
- GI
- Vascular smooth muscle
- Skeletal muscle
- Ciliary body of eye
What do selective BB target?
beta 1
(cardioselective)
What do non-selective BB target?
beta 1&2
3 examples of selective BB
atenolol
esmolol
metoprolol
3 examples of non-selective BB
propanalol, sotalol, timalol
How do BB slow HR?
BB effect the cardiac nodal tissue (contain BR) which controls the conduction of the heart. BB slow this conduction.
- monitor for AV blocks like 2 or 3 degree and severe bradycardia
- they can mask tachycardia in hypoglycemic episodes in diabetics
How do BB decrease the strength of contractions? What should I look out for?
BP are in cardiac myocytes which control the contraction strength of the heart. BB make the contraction weaker which eases the workload on the heart and decreases the myocardiums oxygen consumption
- watch for development or worsening of HF, don’t give to patients with uncompensated HF or cardiogenic shock
How do BB lower BP? What should I look out for?
BR are in the juxtaglomerular cells of the kidneys. BB prevent angiotensin II from being created in the RAAS because it inhibits the release of renin.
Angiotensin II normally causes vasoconstriction but there will be vasodilation instead, and the influence of aldosterone will be decreased, decreasing blood volume so therefore blood pressure.
- watch for hypotension
How do BB decrease intraocular pressure?
The ciliary body of the eye has beta 2 receptors. Ciliary body is responsible for the production of aqueous humor. In pt’s with glaucoma, the high eye pressure is due to a high amount of aqueous humor in collecting in the eye. Non-selective beta blockers decrease the production of aqueous humor.
How do BB cause bronchoconstriction?
Non-selective affect beta 2 receptors on the bronchioles of the lungs.
- do not give these medications to pts with asthma or COPD
What are BB used for?
HTN, stable angina, dysrhythmias, HF, glaucoma, migraines, tremors, anxiety
