Alpha blockers and calcium channel Blockers Flashcards
Alpha and beta receptor affinities
Alpha - norepinephrine, epinerphine, isoproternol
Beta - isoproterol, epinerphone, norepinepnre
Where do alphablockers work?
A1 - noradrenaline will cause vasoconstriction
-this is to resistance vessels, so will decrease blood flow to certain organs e.g kidney, skeletal mucle and wil increase blood flow to heart and other regions (overall increase in BP)
Alpha blockers - inhibit sympathetic mediated stimulation of vasoconstriction to cause vasodilation which decreases blood pressure
Effects of alpha 1 receptors
- blood vessels - vasoconstriction
- heart - increase contractility
- kidney - vasoconstriction (less blood flow going to kidney)
Post synaptic (vasoconstriction of viens and arterioles to increase BP)
A1 - a - prostate
A1 - b - vascular smooth muscle
Pre and post synaptic
A2 - inihibit noradrenaline adn insulin release on pre synaptic cells
How this receptor works
- due to AP, calcium goes into cell, get vesicle w noradrenaline binding to cell membrane
- released into intersynaptic cleft
- and then will bind to Alpha 1 receptors
- will get an increase in g protein, then cAmp , and over all get increase in calcium and get conraction - vasoconstriction
Names of alpha 1 anatognists
- doxazosin
- tamulosin - a1a specific - for prostate symptoms - when prostate gets larger - can vasodilate this
-all vasodialtors and will be used for hypertension to lower BP
What are alpha 1 blockers good to be used for?
- to treat hypertension
- in combination with other drugs use with an ace inhibitor, and diuretic
Doxazosin
- reversible
- much greater affinity for a1 than a2
- vasodilator
- reduces prostate symptoms
Side effects
-hypotension, dizziness - when stand up
Combined alpha and beta blockers
- Labetalol - used for hypertension in pregnancy, very safe
- Carvedilol - important drug for heart failure
Senario to use alpha blocker
- older patient
- blood pressure not very well controlled on first line therapy - ace inhibitor and thiazide diuretic
- could add in doxazosin
- warning - could get dizzy when stand up too fast - and take it at night just before sleep
What do calcium channel blockers do?
used for hypertension - can vasodilate
- also for angina - because it decreases cardiac work and causes vasodilation
- arrythmias - supraventriculartachyarrhthymias - atrial fibrilation and flutter
How do they work?
- inhibit voltage dependant channels (L type calcium channels)
- normally get calcium coming into cell to get vasoconstriction
- these are found in cardiac myocytes, vascular smooth mucle, also in conducting tissue (sa, av node), also in resistant muscles
- decrease peripheral resistance, decrease BP
- decrease cardiac contractility and SA and AV node transmission
side effects
can cause constipation due to decrease smoth muscle contraction in bowel
different types of calcium channel blockers
Nifedipine, felodipine, amoldipine
- resistance vessels (vasodilation, decrease BP) also works on coronary arteries to get anti-anginal effects
-Side effects - flushign in face (vasodilation), headache, oedema
Verapamil
-cardiac tissue - decrease inotropy and HR
-side effect - constipation
Diltiazem
-does both effects above
What can you give for rapid tachycardia?
- IV - diltiazem and verapamil - rapidly brings down heart rate and cardiac work
