Elimination of Lipophilic and Hydrophilic Substances

Presystemic elimination refers to the fraction of drug absorbed that is excluded from the general circulation by biotransformation or by first-pass binding. 

Presystemic elimination diminishes the bioavailability of a drug after its oral administration. Absolute bioavailability = systemically available amount/ dose administered relative bioavailability = availability of a drug contained in a test preparation with reference to a standard preparation. 

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Drug Concentration in the Body as a Function of Time. First-Order (Exponentiai) Rate Processes 

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