Which term refers to a drug interaction where one drug diminishes the effect of another?

• A. Indication
• B. Contraindications
• C. Adverse Effect
• D. Antagonism

Answer: (D)

One drug diminishing another’s effect is described as antagonism. This means the presence of one medication reduces the action of the other, either by blocking the receptor that the other drug acts on (pharmacodynamic antagonism) or by altering the other drug’s levels in the body so it can’t produce its full effect (pharmacokinetic antagonism). A common example is an antagonist drug that blocks opioid receptors, reducing or reversing opioid analgesia.

Indication refers to the appropriate use or purpose of a drug. Contraindications are situations where a drug should not be used due to risk. An adverse effect is an unwanted, often harmful, effect of a drug. None of these describe a drug interaction that weakens another drug’s effect in the way antagonism does.