Type D reactions are delayed and take time to develop; for example tardive dyskinesia.

Type D reactions are delayed and take time to develop; for example tardive dyskinesia.

• A. They are immediate
• B. They take time to develop, such as tardive dyskinesia
• C. They are dose-dependent
• D. They are reversible

Answer: (B)

Type D reactions are delayed adverse effects that appear after prolonged exposure to a drug or even after withdrawal, reflecting long-term adaptive changes rather than immediate pharmacologic action. Tardive dyskinesia is a classic example, typically emerging after months or years of antipsychotic therapy and often persisting after the drug is stopped. This delay distinguishes them from immediate, dose-related effects and from reactions that are quickly reversible with dose changes. While there can be a relationship to cumulative exposure, the defining feature is the late onset, not rapid appearance or guaranteed reversibility.

Type D reactions are delayed adverse effects that appear after prolonged exposure to a drug or even after withdrawal, reflecting long-term adaptive changes rather than immediate pharmacologic action. Tardive dyskinesia is a classic example, typically emerging after months or years of antipsychotic therapy and often persisting after the drug is stopped. This delay distinguishes them from immediate, dose-related effects and from reactions that are quickly reversible with dose changes. While there can be a relationship to cumulative exposure, the defining feature is the late onset, not rapid appearance or guaranteed reversibility.