Drug levels and HIV

July 2001     View PDF     En español

Drug levels inside cells (intracellular)

Another possible complicating factor about TDM is the recent finding of protease inhibitor levels inside cells, similar to what has been seen with NRTIs. To date, nobody has shown a connection between protease inhibitor levels inside cells to anti-HIV response, but those studies are now being done. It is also not known if there’s a connection between protease inhibitor levels found in blood to those found inside cells.

Human cells have certain genes called P-glycoprotein (P-gp) and Multi-drug Resistance Proteins (MRPs). They control what substances, including drugs, can get into cells and how quickly they’re expelled in order to protect the cells from toxic substances.

It’s still not clear how these genes play a role in the overall effectiveness of anti-HIV therapy, although it is thought they factor in how well drugs are absorbed and how efficiently they get into certain parts of the body, like the brain. These genes already play a major role in the effectiveness of therapies for other diseases. For instance, a high expression of these genes has been shown to make cancer cells more resistant to traditional drugs.