A new drug is found to be highly lipid soluble. It is metabolism it is lower rate of 10% Per hour. On intravenous injection in produced general anaesthesia that lasts only for 15 minutes. The sho duration of anaesthesia is due to
First, the core concept. The question is about pharmacokinetics, specifically drug distribution and elimination. The drug is lipid-soluble, which affects its distribution, and has a metabolism rate of 10% per hour. The short duration of anesthesia despite slow metabolism suggests that distribution is the key factor.
Next, why the correct answer is right. The drug's high lipid solubility means it's quickly distributed into tissues, especially fatty tissues. Even though it's metabolized slowly, the rapid distribution leads to a quick decrease in plasma concentration, thus ending the effect. This is the redistribution theory, common with inhaled anesthetics like nitrous oxide.
For the wrong options, the user mentioned options A to D but didn't list them. Assuming the correct answer is C, the incorrect ones might be related to metabolism, protein binding, or other factors. Need to explain why those are wrong. For example, if an option says metabolism is the reason, that's incorrect because the metabolism rate is given as slow. If another option mentions protein binding, but the drug is lipid-soluble, so it's more about tissue distribution.
Clinical pearl: Remember that lipid-soluble drugs redistribute quickly, which affects duration. This is a key point in anesthetic pharmacology exams.
Need to structure all this into the required sections with bold labels and proper formatting. Check the character count to stay within limits. Ensure each section is concise and precise, using medical terms correctly.
**Core Concept**
The question examines **pharmacokinetics of lipid-soluble drugs**, focusing on **distribution and redistribution** rather than metabolism. A drug's duration of action depends on its plasma concentration, which is influenced by tissue distribution, especially in fatty tissues for lipid-soluble agents.
**Why the Correct Answer is Right**
The short duration of anesthesia (15 minutes) despite slow metabolism (10% per hour) is due to **rapid redistribution**. Once administered intravenously, the lipid-soluble drug quickly distributes into fatty tissues, lowering plasma concentrations and reducing its effect. This is a classic mechanism seen in volatile anesthetics and intravenous agents like **propofol**, where tissue redistribution—not metabolism—terminates action.
**Why Each Wrong Option is Incorrect**
**Option A:** *Metabolism rate is too fast* – Incorrect. The question states metabolism occurs at **10% per hour**, which is slow, not fast.
**Option B:** *High protein binding* – Incorrect. Protein binding would prolong duration by reducing free drug concentration, not shorten it.
**Option D:** *Rapid excretion via kidneys* – Incorrect. The drug’s lipid solubility suggests it is not water-soluble enough for rapid renal excretion.
**Clinical Pearl / High-Yield Fact**
**Lipid solubility ≠ duration of action.** Remember: **"Redistribution beats metabolism"** in lipid-soluble drugs. Anesthetics like **nitrous oxide** and **sevoflurane** terminate quickly due to redistribution into fatty tissues, not hepatic clearance.
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