How is "tolerance" defined in pharmacology?

In pharmacology, "tolerance" specifically refers to the phenomenon where a patient requires higher doses of a drug to achieve the same level of effect that was initially experienced at lower doses. This occurs as the body becomes accustomed to the drug, leading to adaptations that diminish its effects over time.

As a patient continues with drug therapy, their body may adjust in several ways, such as through changes in drug metabolism or receptor sensitivity, which can necessitate an increase in dosage to maintain the desired therapeutic effect. Understanding tolerance is crucial for healthcare providers when managing long-term medication regimens, as it helps to prevent ineffective treatment or potential overdose by acknowledging the need to adjust dosages appropriately.

The other options do not accurately capture the definition of tolerance. A decrease in drug effectiveness over time may occur, but without the context of dose adjustments specific to tolerance. Gradual withdrawal from medication refers to dependence rather than tolerance, and a constant response to drug treatment suggests stability rather than the inherent changes associated with developing tolerance.