Nitrates | Mind map
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Welcome back guys.
In this video we will make a very basic mind
map of nitrates.
A group of drugs commonly used in angina.
Drugs in nitrate group are glyceryl trinitrate
or nitroglycerine, isosorbide dinitrate, isosorbide
mononitrate, pentaerythritol tetranitrate
and erythrityl tetranitrate.
Lets see mechanism of action and effects of
They generate nitric oxide in body.
Nitric oxide activates cytosolic guanylyl
cyclase which increases cGMP level.
This causes smooth muscle relaxation at multiple
Main effect is venodilatation.
This decreases venous return, leading to decreased
end diastolic volume.
Resultant decrease in preload decreases cardiac
There is also some arteriolar dilatation.
This decreases total peripheral resistance
resulting in decreased afterload.
This also contributes in decreased cardiac
Gastrointestinal and biliary track smooth
muscles also get relaxed.
Increased cGMP level in platelets decreases
Now lets talk about pharmacokinetics.
When given by oral route, they undergo extensive
first pass metabolism liver.
Exception in this is isosorbide mononitrate
which undergo a little first pass metabolism.
Sublingual route avoids first pass metabolism
and produces quick response.
Coming to duration of action.
Glyceryl trinitrate is very short acting with
plasma half life of about 2 minutes.
All other nitrates are comparatively longer
Now lets move to uses of nitrates.
They are used in angina.
For acute attack of angina, glycerin trinitrate
is given by sublingual route.
For chronic prophylaxis, long acting nitrates
are given orally.
In classical angina, they provide benefit
by reducing oxygen demand by decreasing cardiac
work as we saw in mechanism of action.
In variant angina dilatation of coronary artery
improves oxygen supply to heart.
Other uses are congestive heart failure, esophageal
spasm, biliary colic and cyanide poisoning.
These were the uses.
Now lets see adverse events with nitrates.
A common adverse event is headache due to
dilatation of meningeal vessels.
Next is hypotension due to vasodilatation.
Postural hypotension leading to weakness and
dizziness occur with nitrates.
High dose of nitrates can cause excessive
hypotension, leading to activation of baroreceptor
This causes tachycardia which can worsen angina.
Next adverse event is facial flushing due
to arteriolar dilatation in face and neck.
They can also cause methemoglobinemia.
Finally, development of tolerance is also
a big problem with nitrates.
It possibly occurs due to reduced generation
of nitric oxide.
It can be prevented by nitrate free interval
of 8-12 hours a day.
So these were adverse events.
Now last point, interactions.
Phosphodiesterase 5 inhibitors like sildenafil,
increase cGMP level and thereby potentiate
the response of nitrates.
So be careful about it.
This completes our mind map of nitrates.
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