PHAR 315 Lecture Notes - Lecture 7: Loading Dose, Digoxin, Diazepam
23 Feb 2016
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Metabolism clears or eliminates the parent drug, even though the metabolites may still be in the body. If hepatic blood flow = 90 l/hr, and clearance of drug x = 45 l/hr: This means that half of the drug entering the liver is irreversibly removed by the liver in one pass. This does not mean that the first 45l is cleared of drug and the last 45 is not. The drug that is extracted from the blood is metabolized by the liver so that the parent compound is eliminated. Extraction ratio = how much of the drug is cleared at each pass through the liver. For drug x, the extraction ratio of 0. 5 would be given. C = plasma drug concentration; cb = blood drug concentration. = cb/c cb = c x . Clearance is the main parameter that determines maintenance dose rate required to achieve the target blood concentration (and therefore the drug effect)
