Concentration of lignocaine used – a) 2%b) 4%c) 5%d) 10%e) 1%
**Core Concept**
Lignocaine is a local anesthetic drug used to block nerve impulses, preventing pain sensation in a specific area. The concentration of a local anesthetic is critical in determining its efficacy and potential toxicity.
**Why the Correct Answer is Right**
The correct concentration of lignocaine for topical application or infiltration anesthesia is **4%**. This concentration is effective for blocking nerve impulses while minimizing systemic absorption and toxicity. Lignocaine works by inhibiting voltage-gated sodium channels, which are essential for the initiation and propagation of action potentials in nerve fibers.
**Why Each Wrong Option is Incorrect**
**Option A:** 2% lignocaine is too low for effective anesthesia and may not provide sufficient pain relief.
**Option C:** 5% lignocaine is too high and increases the risk of toxicity, including central nervous system effects such as seizures and cardiac arrhythmias.
**Option D:** 10% lignocaine is extremely high and can cause severe toxicity, including cardiac arrest and death.
**Option E:** 1% lignocaine is too low for effective anesthesia and may not provide sufficient pain relief.
**Clinical Pearl / High-Yield Fact**
When using local anesthetics, it's essential to remember the "4% rule": 4% lignocaine is the most commonly used concentration for topical application, but concentrations above 4% should be used with caution due to increased toxicity risk.
**Correct Answer: B. 4%**