[nidoqueen]

I am not convinced that chloramphenicol is lipophilic enough to cross the blood brain barrier. Some books and websites say that chloramphenicol can readily cross the blood brain barrier.

At first glance of chloramphenicol's structure, it looks water soluble. I checked the literature as well for calculated Log P values and things don't seem to make sense to me.

I'm aware that the palmitate ester prodrug is commonly employed in clinical use so perhaps books and websites could be referring to that or are they referring to chloramphenicol alone itself? I'm not sure.

Or perhaps chloramphenicol traverses the blood brain barrier through transporter-mediated processes?

I would like some clarification though. Thank you.

[Bidagdha_TADIR]

The prodrug is used to increase absorption from the GIT into the systemic circulation. I don't think the prodrug exists after entering the systemic circulation. So prodrug probably doesn't play great role in BBB crossing.

log P of around 1 is certainly not an indication of a good lipophilic molecule. But it is still better than most beta-lactam antibiotics I think. It's not like that chloramphenicol crosses the BBB better than propranolol or other such drugs, it's like that chloramphenicol crosses the BBB better than most other antibiotics (at that time, now the 3rd and 4th generation cephalosporins are available which can cross the BBB much better). It crossed the BBB better than other antibiotics and therefore was considered for CNS infections. It doesn't mean that it will cross the BBB very effectively (I think that for chloramphenicol the CSF conc. is only 50% of conc. obtained in other body parts).
[Can we really say that a hydrophillic molecule will not cross the BBB - we can't. We can only say that such a molecule will not cross the BBB significantly. Many antibiotics do not cross the BBB significantly and compare to them chloramphenicol is excellent, it doesn't have to be excellent.]