The percentage or fraction of the administered dose of a drug that actually reaches systemic circulation and the rate at which this occurs is the drugs:

Bioavailability.

Explanation:

In pharmacology, drugs are the chemicals used for the treatment of the particular disease. The excessive dosage of the drugs causes the harmful effects in the body.

The bioavailability may be defined as a kind of the subcategory of the fraction and absorptiom of the particular drug. The pharmacokinetics determine the fate of the administered drugs in the living tissue. The doctors always prescribe the proper administration of the drugs.

Thus, the answer is bioavailability.