Lignocaine does not cause following symptoms?

NORCET 1 - 2020

Pharmacology

Medium

Appeared in: NORCET 1 - 2020

Explanation

Constipation is not a recognized side effect of lignocaine.
Lignocaine, a sodium channel blocker, lacks the significant anticholinergic (atropine-like) properties that are the typical cause of drug-induced constipation.
In contrast, other antiarrhythmic drugs like disopyramide are known to cause constipation due to their anticholinergic effects, but this is not a characteristic of lignocaine.

Option A: Lignocaine can cause hypotension, especially in large doses or with rapid IV administration, by depressing myocardial contractility and causing peripheral vasodilation.
Option B: Restlessness is a key sign of Central Nervous System (CNS) toxicity from lignocaine. While initial effects can be drowsiness, higher levels cause CNS excitation, including restlessness, agitation, and tremors, which can precede seizures.
Option D: Nausea and vomiting are known adverse effects of lignocaine. The nausea is often of central origin, meaning it's caused by the drug's effect on the brain.

Visual 1: Table: Summary of Lignocaine Toxicity Signs, categorized into early vs. late and CNS vs. Cardiovascular effects.
Visual 2: Infographic: A diagram showing the progression of lignocaine CNS toxicity from early signs (e.g., numbness, dizziness) to severe signs (e.g., seizures, respiratory arrest).

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Adverse effects of Lignocaine (Lidocaine) as background academic context rather than a clinical decision trigger.
Nurses administering IV lignocaine must continuously monitor for signs of toxicity. Early recognition of symptoms like metallic taste, perioral numbness, or restlessness is critical to halt the infusion and prevent progression to seizures or cardiovascular collapse.
The therapeutic window for lignocaine is narrow. Dosage adjustments are required for patients with heart failure or liver disease, as they have reduced clearance, increasing the risk of toxicity.
What if the patient was on an opioid medication simultaneously? The nurse would need to differentiate the cause of any CNS depression. Opioids cause sedation and respiratory depression, while lignocaine toxicity can start with excitation (restlessness) before progressing to depression. Constipation would more likely be attributed to the opioid.

How to Approach the Question

First, identify the question type. This is a 'negative' question, asking for a symptom that is NOT caused by the drug.
Recall the drug class and primary mechanism of lignocaine (Class IB antiarrhythmic, sodium channel blocker).
Systematically review the major side effect profiles for this drug class. Lignocaine is known for CNS and cardiovascular toxicity.
Evaluate each option against this knowledge: 'Hypotension' is a known cardiovascular effect. 'Restlessness' is a known CNS excitation effect. 'Nausea' is a known CNS/GI effect.
Consider the remaining option, 'Constipation'. This is typically caused by drugs with anticholinergic effects. Since lignocaine does not have significant anticholinergic properties, this is the most likely symptom it does NOT cause.
Select the option that does not fit the known pharmacological profile of the drug.

Concept Tested & Keywords

Concept Tested: Adverse effects of Lignocaine (Lidocaine)
Stem keywords: Lignocaine, symptoms
Lead-in keywords: does not cause
Negative lead-in flag: The question asks to identify the symptom that is NOT caused by Lignocaine.

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