Bioavailability problems

[Asterix]

If you were having bioavailabity problems with a tablet form, would you go for a liquid or something like IV. I was wondering if liquids are absorbed from the stomach etc in the same way as tablets?

[hibernia]

Before the drug can be absorbed it must be released from the tablet formulation. It is worth doing a simple dissolution test, in water and in a slightly acid solution, to see how well the tablet breaks up. Some will remain intact for a long time.

In many cases a liquid formulation will have a higher bioavailability but if there is a general adsorption problem it will require IV administration.

[Asterix]

where is a liquid form absorbed from though

[Nik]

In your armpits.

[Asterix]

lol very funny

[hibernia]

where is a liquid form absorbed from though

Liquid is adsorbed from stomach and small intestine, same as solid dose forms, but you skip the dispersion step. If the solid dose hasn't dispersed/dissolved it can't be absorbed while liquid can. Depends on pH and other factors as well so if a tablet that disperses well isn't adsorbed then chances are the liquid won't be either. You could also try changing from an enteric coated formulation to an uncoated one which will have different bioavailability.

It all depends in the drug and the formulation e.g. phenytoin dose has to be reduced by about 10% if changing to a liquid form but for drugs with a wider therapeutic index there would be no need to adjust.

[Nik]

Sorry Asterix but as it seemed a silly question I gave a silly answer. Anyway I hope hibernia's cleared that up for you.

[johnep]

Well chloral hydrate sometimes given rectally.
also presumably could say that liquid aerosol absorbed in lungs, glyc trin spray absorbed sl.
johnep