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Drug delivery & Pharmacokinetics

raybeez

Bluelighter
Joined
Oct 31, 2004
Messages
334
Hi all,

This is probably a basic pharmacology question, but I was pondering about it, and wondered if anyone knew the answer.

Could someone explain how drug delivery method relates to the pharmacokinetics of a drug in the body? Specifically duration and elimination as a function of oral/nasal/injection/inhalation delivery systems.

Onset seems pretty straight forward, ie you hit your peak serum concentrations faster if you administer something IV versus orally where it would have to make its way through the digestive tract before being absorbed into the blood.

What I was wondering is how duration/elimination changes with delivery method. For example, time from 'peak high' (and I assume peak serum concentration) to baseline from smoking marijuana is drastically different than peak to baseline from ingesting it. Are there different elimination/catabolic pathways (and hence different half lives) for different delivery methods?

This trian of thought was prompted by http://www.awolmachine.com/ and their claims of "no alcohol hangover" due to their inhalation delivery method... afiak its getting burned into acetaldehyde either way, but would the alcohol intoxication duration/elimination paramters be any different?
 
Anything that avoids the stomach/intestines avoids 1st pass metabolism, so you get a higher peak plasma.

Modes of delivery that have a low amount of depot, so that the drug quickly gets into the blood, have short half lives (I.V vs subcutanous, fat injection or oral). Likewise they have shorter absorption phase half lives.

The idea that awol machines have no hang over is more likely to come from the fact that they use purer alcohol, so no nasty sugar congeners in there. And because the elimination half live will be quicker, you're not going to be drug for as long, which means less dehydration.
 
The 'no hangover' thing is a bit rich. AFAK the metabolism is the same only ingestion is not usually considered the most efficient form of delivery. Amphetamines contradict this claim but only because they are robust molecules and are easily absorbed through the digestive tract. Shortly after the Moscow theatre raid, a study on fentanyl showed that inhalation of the aerosolized freebase was equipotent to IV administration of the drug. Intranasal administration is by far the coolest delivery system for individuals who are opposed to needle use IMO, cf. xylometazoline. After my research project I could be considered qualified to make conformationally constrained pseudoephedine salts. Whilst the synthesis is outside the realm of what would be put to clandestine usage, the project could be of value to the medicinal community. I will consider this as my project if I get into Bockmuhl university in Germany next October.
 

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Have they identified the fentanyl derivitive that was actually used. There was some speculation about it being carfentanyl, but I would imagine that there are quite a few fentanyl derivative that it would be feasable to do such a thing with (just because carfentanyl is the most potent, it doesn't mean that it's the substance actually used)
 
I just thought it was plain 'ol fentanyl but I dont know. There was a report that they were gassing the place for 20 minutes and were thinking of stopping. However when a panicked hostage came running to the door this scared the wits out of them, fearing an explosion. I guess they must of gassed for a further 20 minutes to make sure. But alot of the myths about a fatal dosage lying around in the synthesis of fentanyl is probably not true because it is not especially volatile. Still it not exactly advisable for the chemist to omit wearing gloves and lick his fingers after scraping out the filter cake.
 
That was black humour BTW. After reading how O.D.B. ended up, I dont want to sound to reckless now do I?
 
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