MANDL'S THROAT PAINT

 

medicinal preparation containing iodine.

Mnemonic for Mechanism

"Ions Denature Membranes and DNA"

• Ions: Oxidation by iodine ions.
• Denature: Proteins and enzymes are denatured.
• Membranes: Lipid damage increases permeability.
• DNA: Direct damage halts replication.

Oxidation of Cellular Components

• Iodine acts as a strong oxidizing agent.
• It disrupts the sulfhydryl (-SH) groups in enzymes and proteins of microorganisms, leading to the inactivation of these vital components.
• Sulfhydryl (-SH) groups, present in the amino acid cysteine, play a critical role in the structure and function of enzymes and proteins in microorganisms.

Basic Information

• Symbol: I
• Atomic Number: 53
• Physical State: A shiny, purple-black solid at room temperature that sublimates into a violet gas.

 Forms of Iodine

• Elemental Iodine (I2): Used in antiseptics and laboratory settings.
• Povidone-Iodine: A stabilized form for medical applications.
• Potassium Iodide (KI): Used in supplements, radioprotection, and hyperthyroidism treatment.
• Lugol’s Solution: A mixture of iodine and potassium iodide for therapeutic uses.

Iodine (I₂) vs. Iodide (I⁻)

Iodine and iodide are two forms of the same element, but they differ in their chemical structure, properties, and uses. Here’s a comparison:

• Iodine (I₂):

  • Molecular form of iodine.
  • Exists as a diatomic molecule (I₂).
  • Neutral, non-ionized form.
  • Insoluble in water but soluble in organic solvents like alcohol.

• Iodide (I⁻):

• Ionic form of iodine.
• A negatively charged ion.
• Water-soluble due to its ionic nature.

Biological Role

• Iodine (I₂):

  • Not directly used in the body; must be converted to iodide (I⁻) to participate in physiological processes.

• Iodide (I⁻):

• Absorbed in the gastrointestinal tract.
• Taken up by the thyroid gland for the synthesis of thyroid hormones (T3 and T4).

5. Safety and Toxicity

• Iodine (I₂):

  • Direct exposure can irritate the skin, eyes, and respiratory tract.
  • Overuse in antiseptics may lead to iodism (toxicity).

• Iodide (I⁻):

• Safer for internal use.
• Chronic high doses can disrupt thyroid function (hyperthyroidism or hypothyroidism).

Mnemonic to Remember

"Iodine for Outside, Iodide for Inside":

• Iodine (I₂): Topical and external antiseptic.
• Iodide (I⁻): Internal use for thyroid and deficiency treatment.

Mnemonic for Lugol's Iodine Uses

"Thyroid, Topical, Test"

• Thyroid: Hyperthyroidism, thyroid storm, radioprotection.
• Topical: Antiseptic for wounds and infections.
• Test: Schiller’s test for cervical health.

Mnemonic to Remember

"Lugol for the Thyroid, Mandl for the Mouth"

How Iodine Penetrates Microorganisms Quickly

Iodine's rapid penetration into microorganisms is due to its unique chemical properties and mechanism of action. Here's an explanation:

 Molecular Size and Solubility

• Small Molecule: Iodine (I₂) is a small, non-polar molecule that can easily pass through cell membranes, especially lipid layers.
• Lipid Solubility: It dissolves well in the lipid bilayer of microbial membranes, facilitating quick entry into cells.

Oxidative Properties

• Iodine is a strong oxidizing agent.
• Once inside the microorganism:
  • It reacts with and disrupts sulfhydryl (-SH) groups in proteins.
  • It modifies nucleic acids, damaging DNA and RNA.
• These reactions occur rapidly, leading to microbial inactivation within seconds to minutes.

 Disruption of Cell Membranes

• Iodine interacts with the lipids in microbial membranes, compromising their structural integrity.
• This increases membrane permeability, allowing further penetration and leakage of cellular contents.

Iodide Conversion

• In solutions (e.g., Lugol’s iodine or povidone-iodine), iodine dissociates into free iodine (I₂) and iodide ions (I⁻):
  • Free Iodine (I₂): Penetrates rapidly due to its non-polar nature.
  • Iodide (I⁻): Provides sustained action by continuously releasing iodine.

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5. Synergistic Effects

• Iodine attacks multiple cellular targets simultaneously (proteins, enzymes, nucleic acids), overwhelming the microorganism and accelerating its destruction.

Mnemonic for Oxidation

"LEO the lion says GER"

• Loss of Electrons is Oxidation.
• Gain of Electrons is Reduction.

 Why Iodine Is an Effective Oxidizing Agent

• Electronegativity: Iodine is sufficiently electronegative to accept electrons but less reactive than chlorine, making it safer for certain applications.
• Stability of Iodide ($I^-$): Once reduced, iodide ions are stable in aqueous solutions.

What Does "Electronegativity" Mean?

Electronegativity is the ability of an atom to attract shared electrons toward itself in a chemical bond. It is a fundamental concept in chemistry that explains how atoms interact in molecules.

Mnemonic for Periodic Trend

"FONCl BrISCH"

• Fluorine > Oxygen > Nitrogen > Clorine > Bromine > Iodine > Sulfur > Carbon > Hydrogen.

This is the order of decreasing electronegativity for commonly encountered elements.