Which term relates to what is occurring in a patient with a substance use disorder who no longer responds to the effects of the substance?

Choice A reason: Addiction refers to the compulsive use of a substance despite harmful consequences. It involves psychological and behavioral components but does not specifically describe the diminished response to the substance. Choice B reason: Intoxication describes the acute effects of a substance on the body and mind, typically occurring shortly after use. It does not reflect the long-term adaptation that leads to reduced responsiveness. Choice C reason: Tolerance is the correct term. It describes the phenomenon where repeated use of a substance leads to a reduced effect, requiring higher doses to achieve the same response. This is a hallmark of physiological adaptation in substance use disorders. Choice D reason: Withdrawal refers to the symptoms that occur when a substance is abruptly discontinued after dependence has developed. It is distinct from tolerance and occurs after cessation, not during continued use.