Final answer:
The fastest and most predictable method of administering a drug is through intravenous (IV) injection.
Step-by-step explanation:
The fastest and most predictable method of administering a drug is through intravenous (IV) injection. When a drug is administered intravenously, the plasma concentration of the drug peaks very quickly and then gradually decreases over time. This method allows for immediate and precise delivery of the drug into the bloodstream, bypassing the gastrointestinal tract and ensuring rapid onset of action.