Bioavailability v. method of ingestion

[samsa]

Swim once was this info on the web, but it is now lost to him. Hes been searching for the last 30 mins with no results, but maybe someone knowledgeable here has the answer.

swim is curious as to the % of bioavailability for each method of ingestion. He is writing a paper so he needs an accurate confirmed amount for each.
He knows IV is 100%, of course, but needs info on IM, insufflation, anal, smoked, and oral. Your cited responses are very much appreciated.

Cheers.

[Shampoo]

There are a cacophony of factors regulating bioavailability other than route of administration including pKa, OIL v. H2O solubility, enzymatic availability...etc.

For instance, the pKa- the pH at which 50% of the drug is ionized (thus unable to permeate membranes)- of a drug may determine in which compartment of the body it is most bioavailable. While some drugs may be completely ionized in the stomach (acidic pH) and not at all in the rectum (neutral-basic), other drugs may be completely ionized in the rectum, and not at all in the stomach. Bioavailability is thus dependant on more than just oral v. rectal administration (or any other route)- one factor of which is pKa and pH (See "pKa, pH and LSD" for a more comprehensive thread on this phenomenon).

Just one example...other than direct infusion into systemic circulation (i.e. I.V), no route of administration has an absolute bioavailability.

[samsa]

Very educational, Shampoo, but swim thinks he worded his question poorly.
For instance, he found this graph on the National Institute of Health's site, but doesnt know how reputable it is and also needs some statistics. I am looking at the efficiency of any route of ingestion broken down.

[thebige]

Swim is far from a chemist.....
but isn't the substance considered first?

[lenses]

Bioavailability is dependent on method of ingestion.

I think the best way to approach this paper would be to give examples with a chemical using different MOI's , and citing the Bioavailability with each one...

But we're not here to help you (or your friend) do their homework.

It would help if your question was a little clearer , as well.

-lenses

[Amazing Andy]

Without looking anything up, I know for a fact bioavailability differs for a given chemical even amongst similar substances such as opiates. With exceptions, the trend is that IV usually is highest often at or near 100%, rectal and oral routes tend to be higher than smoking or insuffulation but these can vary wildly depending on the drug. For example, oxycodone has high oral bioavilability for an opiate, up to 87% but nasal is below 50%, while amphetamines are the opposite with oral rates 60% or lower and nasal rates as high as 80%. Smoking rates vary perhaps the most with 2-10% with marijana to up to 90% for PCP and speed, or even 100% in the case of crack cocaine.