How long does it take a brain to down regulate brain receptors with drug use?

Question

I know what down regulation is, I want to know how quickly the brain responds to people taking different drugs. Specifically opiate drugs such as Percocet, Vicodin, etc.

Answer 1

It depends on the cell type and the drug but changes can be detected in minutes and strong changes can be detected in hours. True drug tolerance to moderate doses of drugs takes on the order of days to weeks. This is the time frame that is most important clinically. There are probably also developmental, semi-permanents changes that take months to years but those are poorly understood.

Answer 2

As per the answer above, downregulation occurs rapidly on a cellular level, but there seems to be more involved in tolerance than receptor downregulation/degradation.  Receptors can be internalized within minutes, and at saturating doses of a drug, the majority of the receptors can be gone within the hour.