This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Unknown
[{'content': 'LD50 /ED50 is - \nSelect and explain. \nA. Therapeutic index, B. Bioavailability, C. Potency, D. Efficacy', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. is \'a\' i.e.. Therapeutic index Therapeutic index o Drugs usually have more than one action. o The maximal response for the different action of a drug may be different ie the DRCs (Dose response curves) for different effects of a drug may be different. o The extent of separation of DRCs of a drug for different effects is a measure of its selectivity, e.g. the DRCs for bronchodilatation and cardiac stimulation are quite similar in case of isoprenaline but far apart in case of salbutamol - the latter is more selective. o The gap between the therapeutic effect DRC and the adverse effect DRC defines the safety margin or the therapeutic index. o In Experimental animals Therapeutic index = Median lethal dose (Ld50) ------------ Median effective dose (Ed50) o But in clinical set up, the therapeutic range is bounded by the dose w hich produces minimal therapeutic effect and the dose which produces maximal acceptable adverse effect. "Therapeutic index is the ratio between the toxic dose and the therapeutic dose of a drug, and is used as a measure of the relative safety of the drug for a particular treatment "', 'role': 'assistant'}]