Pharmacodynamics and mechanism of action
Preparations based on Iodum represent a crucial subgroup of halogen-containing compounds. In medical practice, they are used exclusively as antiseptics. It is important to emphasize that despite their high antimicrobial activity, these agents are not used for disinfecting inanimate objects, but are intended solely for treating biological tissues.
The main active principle is active (elemental) iodine. It possesses a universal spectrum of activity, exerting a detrimental effect on most known pathogens: bacteria, viruses, pathogenic fungi, and protozoa.
The mechanism of antimicrobial action is based on two key pharmacodynamic effects:
- Protein denaturation. Active iodine has the ability to precipitate and coagulate tissue proteins. During this chemical reaction, special complex compounds—iodamines—are formed. The coagulation of microbial cell proteins leads to its inevitable destruction.
- Oxidation. The oxidative properties of elemental iodine additionally provide a powerful antimicrobial effect. However, among halogens, iodine is not the most aggressive oxidizer—in terms of oxidation strength, it objectively falls behind free chlorine and bromine.
Alcoholic solution of iodine (5%) and rules for its use
The most well-known representative of the group is the 5% alcoholic solution of iodine. Upon local application to tissues, it demonstrates a pronounced irritant effect. If the concentration of the active substance is high, the irritant effect naturally transitions into a cauterizing one.
Precisely because of its pronounced cauterizing effect, the use of this antiseptic in surgical and traumatological practice is strictly regulated. The alcoholic solution is used exclusively for treating wound margins.
Applying the preparation directly to the wound surface itself is categorically contraindicated, as the contact of active iodine with exposed tissues inevitably causes chemical burns.
The use of alcoholic solutions carries the risk of local complications. The most common issue is a local irritant effect when treating a large surgical field. In some cases, this can lead to a full-thickness chemical burn of the skin. The risk of such complications increases manifold when using high-concentration solutions, as well as in patients with sensitive skin.
Aqueous solutions of iodine (Lugol's solution)
Since alcoholic solutions are too aggressive for sensitive areas of the body, clinicians have aqueous solutions of iodine at their disposal. A classic example of such an antiseptic is Lugol's solution.
Its composition is fundamentally different from the alcoholic tincture and includes three components:
- Active elemental iodine.
- Potassium iodide.
- Water.
From the standpoint of pharmacological classification, Lugol's solution is also an antiseptic, but the absence of alcohol makes its action milder. The main field of application for this drug is the local treatment of inflammatory and infectious processes on mucous membranes. In clinical practice, Lugol's solution is traditionally used for the gentle swabbing of affected areas of the fauces, pharynx, and larynx, ensuring the sanitization of the infection focus without the risk of deep tissue damage.
Briefly: answers to topical questions
What is the pharmacological role of potassium iodide in Lugol's solution?
- Potassium iodide (Kalii iodidum) is a component of both aqueous and alcoholic solutions of Lugol's solution.
- Pure iodine / elemental iodine (Iodum) is the iodine-containing component of Lugol's solution; iodine-containing drugs belong to antiseptics.
What are the contraindications for the use of iodine preparations?
- Allergy to iodine preparations / iodine intolerance — indicated as a contraindication to the administration of iodine-containing contrast agents and as a contraindication to ERCP.
- Severe bronchial asthma — indicated as a contraindication to contrast administration in upper urinary tract diagnostics.
What modern drugs belong to the group of iodophors?
- Iodinol (Iodinolum).
- Iodonat (Iodonatum).
- Iodovidon.
- Iodopyron (Iodopyronum).
- Jox (Yoks).
What resorptive effect do iodine preparations exert on the body when absorbed into the bloodstream?
- Expectorant effect (Actio expectorans) — when taken orally and absorbed into the systemic circulation, iodine salts stimulate the secretion of bronchial glands, liquefy sputum, and increase the motility of the ciliated epithelium of the respiratory tract.
The rule for treating wounds with an alcoholic solution of iodine: "Margin — smear, center — do not touch!". The preparation is applied only to the wound margins to avoid chemical burns to the wound surface itself.
Class and exam questions
Why must a 5% alcoholic solution of iodine not be poured directly into a wound?
Due to their pronounced irritant and cauterizing effect. The contact of active iodine with exposed tissues causes protein coagulation and a chemical burn, which worsens the trauma. Only the wound edges should be treated.
Can iodine preparations be used to disinfect surgical instruments?
No, halogen-containing compounds of this group are used exclusively as antiseptics for tissue treatment (skin, mucous membranes), and not for the disinfection of inanimate objects.
How does iodine destroy bacteria and viruses?
The antimicrobial effect is achieved in two ways: through the denaturation of tissue and microbial proteins with the formation of iodamines, and through the oxidative properties of elemental iodine.
How does Lugol's solution differ from standard pharmacy iodine?
Lugol's solution is an aqueous solution which, in addition to elemental iodine and water, contains potassium iodide. Unlike the alcoholic solution, it acts more mildly and is used for swabbing mucous membranes (fauces, pharynx, larynx).
What else to study on this topic
- Comparative characteristics of the oxidative properties of halogens (iodine, chlorine, bromine).
- Biochemical mechanism of iodamine formation upon interaction with tissue proteins.
- Risk factors for chemical burns during surgical field preparation.
- Features of the use of aqueous antiseptics for infections of the larynx and pharynx.
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