Which of the following is NOT an amide ?
**Core Concept**
Local anesthetics can be broadly classified into two categories based on their chemical structure: amides and esters. This classification is critical in understanding their pharmacokinetics, metabolism, and potential side effects.
**Why the Correct Answer is Right**
Local anesthetics that are amides have a tertiary amine group linked to an aromatic ring via an amide bond. This structural feature is responsible for their increased stability and reduced toxicity compared to ester local anesthetics. Amide local anesthetics are metabolized by the liver, whereas ester local anesthetics are metabolized by plasma cholinesterase.
**Why Each Wrong Option is Incorrect**
**Option A:** This is an amide local anesthetic. It contains an amide bond linking the tertiary amine group to the aromatic ring.
**Option B:** This is also an amide local anesthetic. It shares the characteristic amide bond, making it an amide local anesthetic.
**Option C:** This is the correct answer. It is an ester local anesthetic, lacking the amide bond that defines amide local anesthetics.
**Clinical Pearl / High-Yield Fact**
When choosing a local anesthetic, it's essential to consider the patient's history of allergy or sensitivity to esters or amides, as this can influence the selection of the local anesthetic.
**Correct Answer: C. This is the correct answer. It is an ester local anesthetic, lacking the amide bond that defines amide local anesthetics.**