What is it called when there is a decreased response to a drug due to repeated use?

The term for a decreased response to a drug due to repeated use is tolerance. Tolerance occurs when a person needs a greater dosage of a drug to achieve the same effect that was initially experienced after a smaller dose. This phenomenon happens because the body adapts to the presence of the drug over time, often leading to a reduction in the drug's effectiveness.

For instance, if someone regularly takes a medication or substance, their body may adjust by altering the way it metabolizes the drug or by changing receptor sensitivity. As a result, individuals may find that the original dose no longer produces the desired effects, prompting them to increase the dosage to regain those effects.

Resistance is typically used in a different context, often referring to pathogens that become less sensitive to the effects of drugs, such as in the case of antibiotic resistance. An allergy involves an unusual immune response to a substance, leading to symptoms that are not related to dosage effectiveness. Dependency refers to a state where the body relies on a drug to function normally, often accompanied by withdrawal symptoms when the drug is not available.