In pharmacology, what is a therapeutic window?

• A. The time between doses.
• B. The maximal dose that can be given.
• C. The range of drug doses that yields efficacy without unacceptable toxicity.
• D. The immediate effect after administration.

Answer: (C)

The therapeutic window is the range of drug doses that yields the desired therapeutic effect without causing unacceptable toxicity. It sits between the dose needed to produce a real benefit and the dose at which adverse effects become a concern, so clinicians aim to stay within this zone when prescribing and adjusting therapies. The width of this window varies: some drugs have a wide window and are forgiving, while others have a narrow window and require careful monitoring and individualized dosing. A useful related idea is the therapeutic index, which reflects how large the safety margin is—the larger the index, the wider the window and the safer the drug tends to be.

The other statements describe different concepts: the time between doses is the dosing interval, not the safety window; the maximal dose is just an upper limit that may not reflect where toxicity actually starts; and the immediate effect after administration refers to onset of action, not the safe, effective dosing range.