A group of student nurses are reviewing the process of drug development. Which statement best identifies the concept of a placebo?

A. Molecular weight: Drugs with lower molecular weight tend to have higher bioavailability because they can more easily pass through biological membranes.

B. Fat or liquid solubility: Drugs that are fat-soluble can cross cell membranes more easily, affecting their bioavailability. Water-soluble drugs may require transport mechanisms, which can limit absorption.

C. Depth of breathing: The depth of breathing primarily affects the absorption of inhaled drugs, not the general bioavailability of orally or intravenously administered medications.

D. Development of a fever: While fever can affect drug metabolism, it doesn’t directly influence the bioavailability of a drug.

E. Presence of food: Food in the stomach can either enhance or inhibit drug absorption, depending on the drug’s characteristics. This directly impacts bioavailability.

A. Therapeutic level: This is the correct answer. It refers to the concentration of a drug in the bloodstream at which it achieves the desired effect without causing toxicity.

B. Therapeutic index: This is a ratio that compares the toxic dose to the therapeutic dose of a drug. It does not refer to the point of optimal effect.

C. Toxic level: This refers to the concentration of a drug at which it becomes harmful or toxic. It is not associated with the desired effect.

D. Therapeutic range: This refers to the range between the minimum effective concentration and the toxic concentration of a drug. It does not pinpoint the optimal effect but indicates the safe range.