TD50 stands for which of the following?

• A. Therapeutic Dose
• B. Toxic Dose
• C. Time-Dependent Dose
• D. Tolerable Dose

Answer: (B)

TD50 is the dose at which toxic effects occur in 50% of individuals exposed to the drug. The 50% indicates the median toxic response on the dose–response curve, so TD50 defines the median toxic dose. This metric helps describe the drug’s safety margin and is used with ED50 (the dose for 50% of the population to achieve a therapeutic effect) to gauge safety; a larger TD50 relative to ED50 suggests a wider margin of safety. It’s distinct from LD50, which is the lethal dose for 50% of subjects. Terms like Therapeutic Dose, Time-Dependent Dose, or Tolerable Dose don’t describe the median toxic response, so the correct interpretation is the toxic dose for half the population.