calcium channel blockers Flashcards
where do we find the L and the T type calcium channels
the L type calcium channels are the long lasting ones. these are found mostly within the cardiac tissue and the smooth muscle cells
the T type are the ones found in the pacemaker cells and the neurons
what are the advantages when using calcium channel blockers as a whole for treatment of cardiac issues
Do not induce bronchoconstriction
* Do not adversely affect lipid profiles.
give me an example of a dihydropyridine
amlodipine. these are the dipine drugs
MOA of amlodipine
these are calcium channel blockers that can act on both the L and T type channels. amlodipine acts to greatly reduce total peripheral resistance as they vasodilate the arterioles.
these drugs have great vasoselectivity as they bind to an inhibit calcium channel activity when they are in the inactivated state.
Ca2+ channels are more likely in the inactivated state in smooth muscle as the depolarisations are greater in length in SM.
why do we beware of dihydropyridines in anigna
they can produce marked vasodilation and a great decrease in TPR resulting in hypotension. this can cause reflex tachycardia and inotropy resulting in increased myocardial O2 demand.
gives us an example of a phenylalkyamine
verapamil
how does verapamil work
it binds to L type calcium channels in their open state. this means this drug is more cardioselective as the L type channels more so exist in the cardiac muscle.
thus depressing the amount of Ca2+ in the cardiac muscle cell. therefore depressing cardiac work and O2 consumption.
verapamil binding promotes inactivated channel formation and slows recovery from the inactivated state hence increasing refractory period of pacemaker cells - as slower upstroke, and decreasing intracellular Ca2+
when would we use verapamil
angina and hypertension
when dont we want to use verapamil
Avoid in In heart failure
Concomitant β-blocker use with a CCB will
Produce a synergistic pharmacodynamic , effect, which will slow heart rate and decrease cardiac contractility
In the presence of bradycardias, conduction defects, etc…, verapamil
admin can further decrease HR and accentuate heart block
verapamil PKs
metabolised by first pass metabolism by CYP3A4 enzymes in the liver. hence given IV to avoid this
can i have an example of benzothiazipines
diltiazem
how does diltiazem work
it interferes with inward Ca2+ flow during depolarisation of cardiac pacemaker cells
is thus effective for rate control during things like AF.
does this by binding to the open Ca2+ channel and inactivates it, making it unresponsive
what is diltiazem good for
AF rate control, good in angina as well, can also reverse coronary vasospasm.
what are some adverse effects of CCBs
bradycardia, hypotension, AV block, heart failure,Don’t use verapamil or diltiazem in conjunction with β-blockers,
cause cardiac depression!
