Chlorhexidine: mechanism of action, spectrum, and application

Mechanism of action

Chlorhexidine differs fundamentally in its mechanism from inorganic chlorine compounds. Its bactericidal effect is realized in three sequential stages that lead to the irreversible destruction of the microbial cell:

First, the antiseptic molecule tightly attaches to the cell membrane of the bacterium.
This interaction disrupts the barrier functions of the membrane, causing a rapid efflux of small vital molecules from the intracellular space outward.
At the final stage, precipitation of cytoplasmic proteins occurs. As a result of this total damage, the microorganism inevitably dies.

Spectrum of antimicrobial activity

The drug has a broad spectrum of activity, yet it has clear limitations regarding microflora susceptibility.

High susceptibility: The antiseptic effectively destroys both gram-positive and gram-negative bacteria. This list includes streptococci, gonococci, bacteroids, and gardnerella. Specific pathogens are also highly susceptible to it: Treponema pallidum, intracellular parasites (chlamydia and ureaplasma), protozoa (particularly trichomonads), and the herpes virus.
Complete resistance: The drug is incapable of dealing with bacterial spores and fungi. It is important to note that Mycobacterium tuberculosis is also resistant to its effects. In addition, the vast majority of viruses (with the exception of the herpes virus) are completely insusceptible to this biguanide derivative.

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Clinical application in medicine

Due to its potent bactericidal action, the drug has become an indispensable tool across several medical disciplines:

In surgical practice: Solutions are used for thorough scrubbing of the operating surgeon's hands and preparation of the surgical field. The agent is also suitable for cold sterilization of surgical instruments. In purulent surgery, the drug is used to treat purulent-septic processes: active irrigation of infected surgical wounds, burn surfaces, and bladder sanitation.
In dentistry: It is prescribed as therapeutic mouthwashes for various inflammatory diseases of the gums and oral mucosa, such as gingivitis, stomatitis, and periodontitis.
In venereology: It serves as a reliable agent for individual emergency prophylaxis of sexually transmitted infections (STIs). Timely use reduces the risk of contracting syphilis, gonorrhea, trichomoniasis, chlamydia, and ureaplasmosis.

Side effects

Despite its high clinical efficacy, topical application of the drug is not always without consequence. Regular hand disinfection by medical personnel may cause adverse skin reactions. The most frequent side effects include marked skin dryness, persistent itching, and the development of contact dermatitis.

Briefly: answers to topical questions

At what concentrations are aqueous and alcoholic chlorhexidine solutions used depending on the indications?

The concentration and type of solution used depend on the clinical indications and the goals of antiseptic treatment.

Chlorhexidine solution — at a concentration of 0.05%, it is used for gargling in meningococcal infection and jet irrigation of the tooth socket in the treatment of alveolitis.
Aqueous-alcoholic solution (Chlorhexidini bigluconas) — at a concentration of 0.5%, prepared from a 20% solution by dilution with 70% ethanol at a ratio of 1:40. Used for preparing the surgical field and disinfecting instruments.
Alcoholic chlorhexidine solution — without specifying the exact concentration, it is the drug of choice for preparing the surgical field during cardiac pacemaker implantation.
Chlorhexidine solution at a concentration of 0.06% is mentioned as a disinfectant solution in which immersing anesthetic carpules is strictly prohibited.

How to memorize

To memorize the spectrum of activity in venereology, use the acronym "SGT-HU": Syphilis, Gonorrhea, Trichomoniasis, Hlamydia (Chlamydia), Ureaplasmosis — these are the main infections for which chlorhexidine is effective for individual prophylaxis.

Class and exam questions

To which chemical group does chlorhexidine belong?

This is a dichlorinated biguanide derivative. In exams, it is important not to confuse it with iodophors, phenol derivatives, or quaternary ammonium compounds.

How exactly does the drug kill a bacterial cell?

The mechanism involves three stages: attachment to the membrane, triggering the efflux of small molecules from the cell, and final precipitation of cytoplasmic proteins.

Can this agent be used to destroy spores and viruses?

Bacterial spores exhibit absolute resistance to the drug. As for viruses, only the herpes virus shows susceptibility; all other viruses are resistant to it.

Is chlorhexidine effective against tuberculosis?

No, Mycobacterium tuberculosis is resistant to this antiseptic, despite the fact that other species of streptococci and bacteria are susceptible to it.

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What else to study on this topic

Comparative characteristics of biguanides and inorganic chlorine compounds.
Mechanisms of natural resistance of Mycobacterium tuberculosis and spores to antiseptics.
Protocols for cold sterilization of surgical instruments with chemical solutions.
Pharmacological prophylaxis of STIs: timing and rules for using antiseptics.
Treatment and prevention of occupational contact dermatitis in surgical personnel.

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Chlorhexidine