Morphine Route of Administration

[ro4eva]

I realize this question has probably been asked and answered a lot on these and other drug related forums (and I have used the search function but figured it wouldn't hurt to ask again) and for that I apologize in advance.

My question is, which of the following do you find is your favorite Morphine RoA:

Oral
Rectal
Nasal

IV and/or SC RoA would obviously be a better choice than the other 3 listed above but for personal reasons I can't IV/SC anymore.

 

[K'd-OUT-in-AZ]

Internasal has a lower bioavailability than oral and rectal has just about the same as oral...so oral.

 

[amapola]

rectal has just about the same as oral...so oral.

30%-40% of Morphine is metabolized in the liver during presystemic metabolism.

 

[K'd-OUT-in-AZ]

30%-40% of Morphine is metabolized in the liver during presystemic metabolism.

And oral Morphine is 25-35%

 

[amapola]

Well you didn't understand my post at all but whatever (morphine getting metabolized is bad).

Anyways as morphine undergoes extensive processing during first pass metabolism I had assumed that rectal administration, which bypasses that, would be much more efficient than oral. That being said having quickly looked on google it seems that you can only expect a slightly bioavailability increase administering rectally, though I can't yet tell why.


edit:
Okay I think I got it. Rectal is better as it results in higher morphine plasma concentration as opposed to oral.
http://www.nature.com/clpt/journal/v54/n3/abs/clpt1993149a.html

However there is also fairly poor rectal absorption in your average colon unless you get a slightly alkaline environment, in which case you can get much better overall results than oral.
http://www.springerlink.com/content/j606n384v5746640/