Ratio of median lethal dose to median effective dose is called?
The core concept here is about therapeutic index. I think the therapeutic index is the ratio of LD50 to ED50. It's a measure of a drug's safety. The higher the therapeutic index, the safer the drug because it means there's a larger margin between the effective dose and the lethal dose.
Wait, why is that the correct answer? Let me confirm. The therapeutic index is defined as LD50 divided by ED50. This ratio helps clinicians understand how much more of a drug is needed to cause toxicity compared to the effective dose. So if a drug has a high therapeutic index, it's safer because you can give a higher dose before it becomes toxic.
Now, the wrong options. Let's say the other options are things like "therapeutic window," "intrinsic activity," or "potency." The therapeutic window is different; it's the range between the minimum effective dose and the minimum toxic dose. Intrinsic activity relates to how strongly a drug activates a receptor. Potency is about the concentration needed to produce an effect.
Clinical pearl: Remember that a higher therapeutic index means a safer drug. So when you're given a drug with a low therapeutic index, you need to monitor it closely because the difference between effective and toxic doses is small. For example, drugs like warfarin or digoxin have low therapeutic indices and require careful monitoring.
**Core Concept**
The question tests understanding of pharmacological safety parameters, specifically the **therapeutic index**, which quantifies the margin between a drug’s toxic and effective doses. It is calculated as **LD₅₀/ED₅₀**, where LD₅₀ is the dose causing death in 50% of subjects, and ED₅₀ is the dose effective in 50% of subjects.
**Why the Correct Answer is Right**
The **therapeutic index (TI)** directly represents the ratio of median lethal dose (LD₅₀) to median effective dose (ED₅₀). A higher TI indicates greater safety, as larger doses are required to reach toxicity compared to efficacy. For example, a TI of 10 means the toxic dose is 10× the effective dose. This metric is critical for risk-benefit assessments in drug development and clinical use.
**Why Each Wrong Option is Incorrect**
**Option A:** *Therapeutic window* refers to the range between minimum effective and minimum toxic doses, not their ratio.
**Option B:** *Potency* describes the ED₅₀ itself (lower ED₅₀ = higher potency), not the LD₅₀/ED₅₀ relationship.
**Option C:** *Intrinsic activity* relates to a drug’s ability to activate receptors, unrelated to dose-response safety metrics.
**Clinical Pearl / High-Yield Fact**
Drugs with a **low therapeutic index** (e.g., warfarin, lithium, digoxin) require therapeutic drug monitoring due to narrow safety margins. Remember: **TI = LD₅₀/ED₅₀** is a foundational concept in pharmacology exams.
**Correct Answer