When reading about a drug, you see the statement: "When administered orally at the recommended dose, the bioavailability of this drug is 75%." What does bioavailability mean?
Only 75% of the administered dose is absorbed and reaches the systemic circulation.
Seventy-five percent of the administered dose is excreted unchanged, the rest (25%) of the dose is metabolized.
It will cause only 75% of the maximum response, compared with a drug that has a bioavailability of 100%.
Only three-quarters (75%) of the patients who receive this drug will respond to it.