The primary driving force for drugs to move from the point of absorption to the site of action is ______, and the primary driving force for drugs to leave the site of action following a single dose is ______.

Question

Quizplus · Accepted Answer

Passive diffusion is the mechanism by which 95% of the drugs move through the body, both to the site of action and away from the site of action.Passive diffusion is based on concentration gradients across membranes.For example, when a drug is administered and enters the blood stream, the drug's concentration in the blood stream is much higher than it is in extravascular fluids.Therefore, the drug will begin to diffuse out of the blood stream into extravascular fluids and then to the site of drug action.Likewise, as the drug is diffusing toward the site of action, it is also diffusing into other compartments in the body or being eliminated from the body.Thus a point will be reached following a single dose where the drug is in greatest concentration at the site of action.Therefore, it will begin its diffusion from the site of action into extravascular fluids and then into the blood stream.At this time, the drug concentration at the site of action will decrease to a point where the action of the drug will no longer occur.

The Primary Driving Force for Drugs to Move from the Point