Pharm Questions...

[Bagster]

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I am studying pharm now and I was just confused one thing...

Why are some drugs for fast action not used via IV? E.g nitrates?
I tried looking this up online but all I found were studies about the effectiveness of sublingual nitrates versus IV other drugs

Are the nitrates too strong to be used IV? Or is it a chemical problem?

 

[jllander]

The only thing I found on IV nitrates is that they take too long to act when you are treating for acute angina. Also, nitrates in the form of IV or transdermal can actually cause tolerance to develop.

 

[Bagster]

The only thing I found on IV nitrates is that they take too long to act when you are treating for acute angina. Also, nitrates in the form of IV or transdermal can actually cause tolerance to develop.

Interesting...I wonder why....Unless sublingual goes directly into jugular venous system then to heart..

Thanks for the help btw!🙂

 

[sdn1977]

I'll try to help.....I'm a pharmacist.

But...I don't clearly understand your question. Why are fast acting nitrates not used....when/where? In the acute/ICU phase???? Or in the outpt side? And...as opposed to what other drugs?

IV ntg is used far more frequently than sl ntg in the acute hospital setting, but is unrealistic in the outpt setting.

Likewise....sl nitrates have their own issues in the outpt site - they aren't long acting.

Help me understand your question & I'll try to help you understand their application.

 

[Droopy Snoopy]

I'm confused too. Most people won't be anywhere near an IV when they get angina. Since a pill won't work because of the liver metabolism, it's practical to have it sublingual or in a cutaneous patch form. But plenty of vasodilators are used intravenously.

 

[Bagster]

I'm confused too. Most people won't be anywhere near an IV when they get angina. Since a pill won't work because of the liver metabolism, it's practical to have it sublingual or in a cutaneous patch form. But plenty of vasodilators are used intravenously.

Ah. That makes sense.

Let me try to clarify, here is my question: you have a patient in a hospital setting. They have an angina "attack". Why is nitroglycerin used sublingually? Why couldn't you just shoot it through an IV?

I hope that makes it clear...I mean I don't know that many techinical terms, being an MS-1...

 

[Bagster]

I'll try to help.....I'm a pharmacist.

But...I don't clearly understand your question. Why are fast acting nitrates not used....when/where? In the acute/ICU phase???? Or in the outpt side? And...as opposed to what other drugs?

IV ntg is used far more frequently than sl ntg in the acute hospital setting, but is unrealistic in the outpt setting.

Likewise....sl nitrates have their own issues in the outpt site - they aren't long acting.

Help me understand your question & I'll try to help you understand their application.

Actually, nvm. You just answered my question right here.

Thanks!

 

[infiniti]

I am sure the answer is more complex, but generally IV administrations gives 100% bioavalability which generally speaking, correlates to higher distribution into different bodily compartments. This can easily lead to toxicity especially when there is very little tolerance (metabolism/excretion).

Drugs that affect multiple pathways, organs, reations are used with extreme caution because you can mess with lot of other processes even though you are only interested in treating a specific condition.

 

[sdn1977]

I am sure the answer is more complex, but generally IV administrations gives 100% bioavalability which generally speaking, correlates to higher distribution into different bodily compartments. This can easily lead to toxicity especially when there is very little tolerance (metabolism/excretion).

Drugs that affect multiple pathways, organs, reations are used with extreme caution because you can mess with lot of other processes even though you are only interested in treating a specific condition.

Altho your contention is often the case - that IV administration give 100% bioavailability which might correlates to higher tissue distribution & can lead to toxicity, etc....

With ntg....this is one CRAZY drug. The volume of distribution is large (3L/kg) & is cleared more rapidly than liver blood flow (1L/kg/min-extra sites of metabolism are rbcs & vascular walls), so the half life is about 3 min. In addition, depending on what parameter you are looking at, tolerace develops rapidly (particularly an issue with long term ICU IV use). Combine that with the drug being EXTREMELY unstable....you have a drug that really has no purpose in an outpt setting as an IV, unless its in a clinic crash cart. The sl tablets are very effective since they are absorbed directly into the blood & go right to the coronary arteries, but they lose their effectiveness rapidly if the cap is opened too often since the ntg absorbs moisture from the air, the oral & topical products provide unstable absorption & the sl spray is difficult to use in an acute case of angina. They've tried them all & out outpt mainstay is sl ntg for acute episodes.

However...for longer maintenance of an outpt angina pt, if you want to stay with a nitrate, you look for more stable products - like isosorbide dinitrate or mononitrate. (Isordil, Isorbid, Monobid, etc..)

So....on a side note....when you are interviewing your pt & he is using or wants to use a drug for ED (Viagra, Cialis, Levitra) you want to review his drug list not just for nitroglycerin, which is obvious...but also Isordil - it too is a nitrate.