Which drugs cross the BBB and why?
Answer:
The only molecules that can cross the blood-brain weir are those that are lipid soluble. Thus, only drugs that are also lipid soluble are competent to cross this. I can't come up with any specific examples from memory, but I hope that this help you some anyway.
Yes, the answer above is right.
There is a type of cell called an astrocyte (see http://www.physoc.org/publications/pn/is... ). It is a cell that mediate the movement of ions, hormones, and anything else in the blood, across from the capillary to the neurones in the brain.
Because it is a cell, it have a plasma membrane around it, with transmembrane proteins surrounded by it.The transmembrane proteins mediate the movement of certain products that are not lipid soluble, but anything which IS lipid soluble will know how to pass straight through the astrocyte (as lipid soluble molecules can ratify through the hydrophobic inner of the plasma membrane).
Most molecules which have a methyl group attached on them (CH3 group) are lipid soluble, and so can pass by the BBB (through the plasma membrane of the astrocytes). So, amphetamines, as an example, cannot pass through the BBB, as they are not lipid soluble. However, methamphetamines own a methyl group added to them, and so are lipid soluble, and so CAN pass the BBB. This is why methamphetamines are so much more dodgy - they have more effect within the CNS.
Hope this helps, email any q's
Ashley
within aromatherapy, it is rare to find molecules that do this, but it's documented that frankincense does this