Extraction ratio
The proportion of a drug removed by an organ on a single pass of that drug through the organ in the blood. The extraction ratio varies between 0 (no drug removed by the organ) and 1 (all drug removed by the organ). The contribution to clearance of a drug by an organ is found by multiplying the extraction ratio by the blood flow through the organ. As such, the maximum drug clearance by an organ, which occurs when the extraction ratio is 1, is equal to the blood flow through that organ expressed as volume per time.
The renal extraction ratio is larger for drugs that are extensively secreted and that are NOT reabsorbed to any great degree. The hepatic extraction ratio is higher for drugs that have a high intrinsic clearance (Clint) value, which indicates that they are good substrates for one or more hepatic enzymes. Such drugs are referred to as high hepatic extraction ratio drugs.
