Final answer:
Tolerance is the term for the body's decreased response to a drug over time, necessitating higher doses to achieve the same effect. It is due to down-regulation and is closely related to drug dependence and issues like TB drug resistance.
Step-by-step explanation:
The term for the body's decreased response to a drug that is given over a period of time is tolerance. This occurs because of the biological principle of down-regulation, where there is a decrease in the number of hormone receptors in response to increased levels of a hormone or a drug in the system. As tolerance develops, a drug user requires more of the drug to experience the same effects that were once achieved with smaller doses. Drug dependence is another related concept where stopping the drug produces withdrawal symptoms, and could be either physical or psychological. Nonadherence to a drug regimen is especially troublesome for treatments like tuberculosis (TB), as it leads to antibiotic resistance, making the disease harder to control.