High-extraction-ratio drug

When there is no extraction from the organ, the extraction ratio will be zero (i.e., F = 0) and when there is complete extraction (i.e., elimination), Cy = 0 and = 1. In general, pharmaceuticals with an extraction ratio of 0.7 or greater are classified as high-extraction-ratio drugs, whereas those with a ratio of 0.3 or lower are... 

However, in severe hepatic disease, not only is hepatic blood flow reduced but the degree of liver damage may influence intrinsic clearance to the extent that it also affects total drug clearance. Consequently, patients with hepatic disease are at particular risk of developing adverse effects to high extraction ratio drugs. 

Note from the equations above that /u becomes a determinant of AUCu, and its thereby effect, only for a high extraction ratio drug given intravenously when the liver is the major route of elimination [Eq. (36)], and for a high extraction ratio drug given orally or intravenously when the kidney is the major route of... 

For high extraction ratio drugs, where CLhep approaches Qhep> J max will be small. For low extraction ratio drugs, Q p is much greater than CLhep and will approximate one. 

Explain the differences between high extraction and low extraction ratio drugs. 

Varices indicate that portal vein blood flow has been diverted away from the liver secondary to portal hypertension. This would have a significant impact on first-pass metabolism, increasing the bioavailability of oral drugs that are usually extensively cleared on first pass through the liver, i.e. those with a high extraction ratio (>0.7). 

Does the drug have a high extraction ratio (>0.7) such that bioavailability may be affected by portal hypertension/varices causing reduced or absent first-pass metabolism ... 

Oxidation drugs 1 Clearance and half-life of drugs with high extraction ratio... 

Some poisonings for which hemoperfusion is preferred are theophylline [35], lipid-soluble drugs, barbiturates [36], and other types of hypnotics/sedatives/tranquilizers. For example, the extraction ratio [inflow concentration - outflow concentration h- inflow concentration] of theophylline is 99 percent with hemoperfusion and only 50 percent with hemodialysis. It should be noted that high extraction ratios may not predict improved clinical outcomes, and there are no controlled studies of hemoperfusion in poisoned patients. 

Induction increases the rate of biotransformation of drugs that have a low extraction ratio and, consequently, decreases their duration of action except when an active metabolite is formed. The clearance and half-life of a drug with a high extraction ratio remain essentially unchanged, while oral bioavailability is reduced. 

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