**Question:** Substantivity of chlorhexidine remains upto

A. 2 hours
B. 4 hours
C. 6 hours
D. 8 hours

**Core Concept:** Chlorhexidine is a cationic bisbiguanide antiseptic with strong affinity for cell membranes, particularly Gram-positive bacteria. Its substantivity refers to the duration of its antimicrobial effect after contact with the skin or mucous membranes.

**Why the Correct Answer is Right:** Chlorhexidine's substantivity is due to its interaction with negatively charged cell membranes, leading to membrane disruption and loss of cell integrity. In the case of dermal application, chlorhexidine binds to skin proteins and persists for a longer period of time.

**Why Each Wrong Option is Incorrect:**

A. 2 hours: This is too short, as chlorhexidine substantivity is significantly greater than this duration.
B. 4 hours: While substantivity is generally longer than this, it is still an underestimation of chlorhexidine's true duration.
C. 6 hours: Similar to option B, this duration is still shorter than chlorhexidine's substantivity.
D. 8 hours: This option is closer to the correct substantivity but still an overestimation.

**Why Chlorhexidine is Superior:** Chlorhexidine exhibits superior substantivity compared to other antiseptics due to its strong affinity for cell membranes and skin proteins, resulting in a prolonged antimicrobial effect.

**Core Concept (repeated for clarity):** Chlorhexidine's substantivity is based on its ability to bind to negatively charged cell membranes and skin proteins, leading to disruption of bacterial cell membranes and reduced bacterial adherence.

**Clinical Pearl:** Chlorhexidine is often used for skin disinfection prior to venipuncture or invasive procedures due to its long-lasting antimicrobial effect, reducing the risk of infection.

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**Core Concept (for reference):** Substantivity refers to the duration of an agent's effect after initial contact with a surface or tissue.

**Why Chlorhexidine is Superior:** Chlorhexidine's substantivity is superior to other antiseptics because it has a strong affinity for cell membranes and skin proteins, leading to a prolonged antimicrobial effect. This makes chlorhexidine an effective choice for skin disinfection before invasive procedures or venipuncture, reducing the risk of infection.