Nitroglycerin vs Nitroprusside

[Protoman2050]

What's the difference b/w nitroglycerin and nitroprusside, other than that NTG doesn't lead to cyanide toxicity if given over extended periods and has multiple ROAs. When would you use one over the other?

Nitropress is faster than NTG, b/c it directly releases NO, while NTG has to be metabolized by aldehyde dehydrogenase, correct?

Thanks,
Doug

 

[BruceD]

** I'm not a medic, you'd be a fool to use my information in the treatment of any patient without finding resources yourself. **

Nitroglycerin I'll use Ng to save typing...

• Clinical Pharmacology: Relaxation of vascular smooth muscle. Affects both arteries and veins, but has a more pronounced effect on veins. This decreases venous return to the heart by encouraging venous pooling. (Reduces Pre-load).
  
• NG --> (via aldehyde dehydrogenase) --> 1,2glyceryl dinitrate + nitrite --> (via other enzymes in the e- transport chain) --> Nitric Oxide. Organic nitrates are eliminated by hepatic nitrate reductase.
  
• Ng : has poor oral bioavailability (ie. don't try swallowing it) and a half life of minutes.
  
• Common forms are sublingual tablets, sublingual sprays, and a paste.
  
• Indications: Ng is typically used for the relief of angina.
  Onset is 2-3mins, peak at 20, duration about 90mins. (spray = shorter; ng paste = longer to onset.) Sustained release forms are preferred for angina prophylaxis (such as isosorbide dinitrate)

Nitroprusside (I'll use Np to save typing)

• Clinical Pharmacology: Acts by the same method as above- vascular smooth muscle relaxation & dilation of peripheral arteries & veins. Selectivity for veins is less than that of Ng. Np produces nitric oxide by interacting with sulfhydryl-containing molecules such as glutathione & cysteine although the specific mechanism is not fully understood.
  
• Np is given intravenously and the reduction in blood pressure is seen w/in a couple of minutes of starting a drip and will drop off very quickly with discontinuation of the drip. t1/2 ~ 2mins.
  Nitroprusside is cleared via a reaction inside red blood cells with hemoglobin (this is the reaction that produces cyanide).
  
• What you must know: Administration of Np warrants continuous BP monitoring, preferably via arterial line.
  Np should never be delivered by gravity fed lines.
  Np *does* cross the placenta & in animal studies has resulted in the death of all ewe fetuses in approximately 1 hr at 25 mcg/kg/min.
  (there are other contraindications as well)
  Np can result in precipitous drops in BP and is therefore usually carefully titrated.
  
• Indications: 1) Immediate reduction in BP of patients in hypertensive crisis until longer-acting blood pressure control drugs can take effect.
  2) Used in the treatment of acute congestive heart failure.

Some References
1. Physician's Desk Reference
2. Nitroprusside on wikipedia: http://en.wikipedia.org/wiki/Sodium_nitroprusside
3. Nitroglycerin on wikipedia: http://en.wikipedia.org/wiki/Glyceryl_trinitrate_(pharmacology)
4. Nitroprusside on RxList: http://www.rxlist.com/nitropress-drug.htm
5. Sodium nitroprusside: mechanism of NO release mediated by sulfhydryl-containing molecules. Grossi L, D'Angelo S. J Med Chem. 2005 Apr 7;48(7):2622-6.
6. The Pearl Dictionary, Matthew Kurlan D.O.

Hope that helps. Vent or Rid may have corrections.

 

[Protoman2050]

** I'm not a medic, you'd be a fool to use my information in the treatment of any patient without finding resources yourself. **

Nitroglycerin I'll use Ng to save typing...

• Clinical Pharmacology: Relaxation of vascular smooth muscle. Affects both arteries and veins, but has a more pronounced effect on veins. This decreases venous return to the heart by encouraging venous pooling. (Reduces Pre-load).
  
• NG --> (via aldehyde dehydrogenase) --> 1,2glyceryl dinitrate + nitrite --> (via other enzymes in the e- transport chain) --> Nitric Oxide. Organic nitrates are eliminated by hepatic nitrate reductase.
  
• Ng : has poor oral bioavailability (ie. don't try swallowing it) and a half life of minutes.
  
• Common forms are sublingual tablets, sublingual sprays, and a paste.
  
• Indications: Ng is typically used for the relief of angina.
  Onset is 2-3mins, peak at 20, duration about 90mins. (spray = shorter; ng paste = longer to onset.) Sustained release forms are preferred for angina prophylaxis (such as isosorbide dinitrate)

Nitroprusside (I'll use Np to save typing)

• Clinical Pharmacology: Acts by the same method as above- vascular smooth muscle relaxation & dilation of peripheral arteries & veins. Selectivity for veins is less than that of Ng. Np produces nitric oxide by interacting with sulfhydryl-containing molecules such as glutathione & cysteine although the specific mechanism is not fully understood.
  
• Np is given intravenously and the reduction in blood pressure is seen w/in a couple of minutes of starting a drip and will drop off very quickly with discontinuation of the drip. t1/2 ~ 2mins.
  Nitroprusside is cleared via a reaction inside red blood cells with hemoglobin (this is the reaction that produces cyanide).
  
• What you must know: Administration of Np warrants continuous BP monitoring, preferably via arterial line.
  Np should never be delivered by gravity fed lines.
  Np *does* cross the placenta & in animal studies has resulted in the death of all ewe fetuses in approximately 1 hr at 25 mcg/kg/min.
  (there are other contraindications as well)
  Np can result in precipitous drops in BP and is therefore usually carefully titrated.
  
• Indications: 1) Immediate reduction in BP of patients in hypertensive crisis until longer-acting blood pressure control drugs can take effect.
  2) Used in the treatment of acute congestive heart failure.

Some References
1. Physician's Desk Reference
2. Nitroprusside on wikipedia: http://en.wikipedia.org/wiki/Sodium_nitroprusside
3. Nitroglycerin on wikipedia: http://en.wikipedia.org/wiki/Glyceryl_trinitrate_(pharmacology)
4. Nitroprusside on RxList: http://www.rxlist.com/nitropress-drug.htm
5. Sodium nitroprusside: mechanism of NO release mediated by sulfhydryl-containing molecules. Grossi L, D'Angelo S. J Med Chem. 2005 Apr 7;48(7):2622-6.
6. The Pearl Dictionary, Matthew Kurlan D.O.

Hope that helps. Vent or Rid may have corrections.

So you'd give Nitropress for pts w/ AMI complicated by MR, VSD, or acute HF, and NTG for uncomplicated MIs?

 

[BruceD]

So you'd give Nitropress for pts w/ AMI complicated by MR, VSD, or acute HF, and NTG for uncomplicated MIs?

If you are asking what you would use it for, you would need to read and follow your local protocols.

Nitropress where I am at is used for control of hypertensive crisis, to create controlled hypotension during surgery (I think), and for certain/specific types of acute congestive heart failure (not high output failure), is administered via pump and closely monitored (via arterial line) because it can lead to a truly precipitous drop in BP. (I'm sorry for repeating myself, but I don't know what training or education you have.)

Nitroglycerin is used (here) for the termination of episodes of acute angina pectoralis secondary to coronary artery disease and is one drug used in the treatment of acute M.I.

But again, those are indications for the drugs, not necessarily what your protocols would allow.

 

[Protoman2050]

If you are asking what you would use it for, you would need to read and follow your local protocols.

Nitropress where I am at is used for control of hypertensive crisis, to create controlled hypotension during surgery (I think), and for certain/specific types of acute congestive heart failure (not high output failure), is administered via pump and closely monitored (via arterial line) because it can lead to a truly precipitous drop in BP. (I'm sorry for repeating myself, but I don't know what training or education you have.)

Nitroglycerin is used (here) for the termination of episodes of acute angina pectoralis secondary to coronary artery disease and is one drug used in the treatment of acute M.I.

But again, those are indications for the drugs, not necessarily what your protocols would allow.

I'm a cardiovascular technology student (I'm learning how to perform in-hospital EKGs, transthoracic ECHOs, how to assist with transesophageal ECHOs, and many other cardiac things). Currently, we're learning cardiovascular pharmacology.

Thanks for the info.