> So how come that the trips lasts 5-12 hs, with negligible blood concentrations? Some drugs are very tightly bound to the receptors they target. (A few are ev

> So how come that the trips lasts 5-12 hs, with negligible blood concentrations? Some drugs are very tightly bound to the receptors they target. (A few are even permanent, so the target protein has to be recycled to turn off the drug.) The blood-brain barrier serves as a one way gate that retains some drugs despite falling blood levels.