Which of the following is NOT part of the factors that influence the Therapeutic Window?

Which of the following is NOT part of the factors that influence the Therapeutic Window?

• A. Absorption rate
• B. Tolerance develops over time
• C. Needing more drugs to obtain desired effect puts the individual at or near the toxic level
• D. Genetic resistance to a drug

Answer: (D)

The therapeutic window is the safety margin between the drug concentration that produces a desired effect and the concentration that causes harm. Factors that influence this window include how quickly and how much of the drug enters the bloodstream (absorption rate), because these affect peak levels and timing of effect; the development of tolerance, since needing more of the drug to achieve the same effect can push dosing toward toxic levels; and using multiple drugs, which can raise overall exposure or cause interactions that increase toxicity risk. Genetic resistance to a drug typically refers to the target organism or cell becoming less affected by the drug. While that resistance can alter how effective the drug is against its target, it does not change the host’s safety margin—the range between effective and toxic concentrations in the patient. So it does not influence the therapeutic window in the same way the other factors do.

The therapeutic window is the safety margin between the drug concentration that produces a desired effect and the concentration that causes harm. Factors that influence this window include how quickly and how much of the drug enters the bloodstream (absorption rate), because these affect peak levels and timing of effect; the development of tolerance, since needing more of the drug to achieve the same effect can push dosing toward toxic levels; and using multiple drugs, which can raise overall exposure or cause interactions that increase toxicity risk.

Genetic resistance to a drug typically refers to the target organism or cell becoming less affected by the drug. While that resistance can alter how effective the drug is against its target, it does not change the host’s safety margin—the range between effective and toxic concentrations in the patient. So it does not influence the therapeutic window in the same way the other factors do.