Pharmacology : ca2+ modulators and organic nitrates

Question 1

what is an organic nitrate case study
method of action /types
(6)

Answer 1

there are three types of organic nitrates which all act to vasodilate blood vessels and decrease cardiac work.

Nitroglycerin
isosorbide mononitrate
Isosorbide Dinitrate

Mode of action :
Nitroglycerin —>receptor on vascular smooth muscle –>cGMP –>blocks ca2+ entry into the cell –>this stops contraction hence allows vasodilation (increasing pre-load)

Question 2

what does a ca2+ channel blocker do ?

6

Answer 2

=>Vascular smooth muscle / coronary arteries :
1- relaxation x smooth muscle as Ca2+ doesn’t enter cells = NO contraction

2-relax coronary arteries = > more blood to the heart = increased perfusion

3-Decreased systemic vascular resistance = decreases after load so there is less work for the heart !

=>Cardiac myocytes = ca2+ channel closed and open slowly = decrease HR

=>Cardiac node tissue = ca2+ cant get into the node so:

• ->SA node : HR reduced
• ->Av node: decreases speed of conduction
• ->helpful in disarrhythmias

Question 3

difference between dihydropyridine and Non-dihydropyridine?
what do they treat?
(4)

Answer 3

They bind to and block L-gated Ca2+ channels

1- Dihydropyridines = Amlodipine = vascular selective ( helps HT/ ANGINA)

2- Non -dihydropyridines (Verapamil , dilimiazem ) = Myocardium selective = favour hyperpolarized cells

\+Antiarrhythmia 
\+HT
\+Angina
\+Migranes 
 both bind to L-type ca2+ channels

Question 4

what are the 3 main organic nitrates ?

Answer 4

1- GTN = glycerol trinitrate
2.ISMN=isosorbide mononitrate
3-ISDN=Isosorbide Dinitrate

Question 5

what should you monitor when treating the patient with ca2+ channel blockers ?
(4)

Answer 5

• reflex tachycardia ( when heart tries to increase CO /BP)
• Orthostatic hypotension
• ECG -1st degree AV block
• Monitor for heart failure (sudden onset weight gain due to fluid, oedema, dyspnea

Question 6

what is NICORANDIL?
what does it do?
(3)

Answer 6

potassium channel opener
1-Opens ATP dependent K+ channels, which means K+ exits the cell
2-Hyperpolarization occurs causing very negative Pd, Ca2+ channels close hence less ca2+ enters cell, increasing the time of hyperpolarisation hence the cell is in a relaxed state for longer
3- also stimulates cGMP so less ca2+ enters cell and hence causes relaxation /dilation of smooth muscle cell

Question 7

What does IVABRADINE DO?

VA

Answer 7

Selective inhibitor x SA current
Effects I funny gated channel = mixed na+/k+ channel = regulated the HR
used for treatment of angina
=slows heart rate and increases time for the depolarisation .