Urine absolute bioavailability from

Example. When potassium penicillin G was administered IV to a group of volunteers, 80% of the 500 mg dose was recovered unchanged in urine. When the same drug was administered orally to the same volunteers, 280 mg was recovered unchanged in urine. What is the absolute bioavailability of potassium penicillin G following oral administration From Eq. (47),... 

The concepmal model for As toxicokinetics requires further clarification. Salient features of the model include the following (1) absorbed As is primarily excreted in the urine. Thus, the UEF, defined as the amount of As excreted in urine divided by the dosed amount, can be used to estimate the ABA. (2) Absolute bioavailability (ABA = AF ) of As from a test material can be estimated from the ratio of UEF of As from test material compared with intravenously dosed As. (3) The RBAs of two orally dosed materials (e.g., a test soil and sodium arsenate) can be calculated from the ratio of their UEFs. This calculation is independent of the extent of tissue binding and biliary excretion ... 

It is clear from discussions so far that knowledge of (AUC)o and/or cumulative amount of dmg eliminated in urine is absolutely essential to assess any type of bioavailability. Both provide an indication of the extent to which the administered dose of a dmg has reached the general circulation. The greater the amount of the administered dose of a dmg that reaches the general circulation the greater will be the value of (AUC)o and the amount excreted in urine. Is it accurate to state that there is a directly proportional relationship between these two parameters ... 

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