chlorhexidine

chlorhexidine. It is a broad-spectrum antiseptic and disinfectant belonging to the biguanide class of compounds. First synthesized in the mid-20th century, it has become a cornerstone in clinical settings for skin preparation and surgical site antisepsis. Its efficacy against a wide range of Gram-positive bacteria, Gram-negative bacteria, and some enveloped viruses underpins its widespread use in hospitals and community healthcare.

Chemical properties and structure

Chlorhexidine is typically available as a salt, most commonly chlorhexidine digluconate, which is highly soluble in water and alcohol. The molecule consists of two symmetric 4-chlorophenyl rings connected by a central hexamethylene chain, with biguanide groups providing cationic charges at physiological pH. This structure is synthesized through a condensation reaction between 1,6-diaminohexane and dicyandiamide, followed by treatment with chloroaniline. In solution, it can form salts with various acids, a property utilized in formulations developed by companies like AstraZeneca and GlaxoSmithKline.

Medical uses

Its primary medical application is as a preoperative skin cleanser, a standard endorsed by organizations like the World Health Organization and the Centers for Disease Control and Prevention. In dentistry, chlorhexidine mouthwash is a first-line treatment for gingivitis and is used to manage periodontitis, often following guidelines from the American Dental Association. It is a critical component in central venous catheter care bundles to prevent bloodstream infections and is used for wound irrigation and in antiseptic bandages. Ophthalmic preparations are used in procedures like cataract surgery.

Mechanism of action

The cationic molecules bind electrostatically to the negatively charged cell walls of microorganisms, disrupting their integrity. At lower concentrations, this causes leakage of intracellular components such as potassium ions and phosphates. At bactericidal concentrations, it causes precipitation of cytoplasmic contents and coagulation, leading to cell death. This action is particularly effective against the lipid bilayer of bacterial membranes, a concept studied extensively at institutions like the Pasteur Institute. Its substantivity, or ability to bind to tissues like oral mucosa and skin, allows for prolonged activity.

Adverse effects and safety

Common local adverse effects include tooth staining, transient taste disturbance, and mucosal irritation, particularly with oral use. Rare but serious hypersensitivity reactions, including anaphylaxis, have been documented in case reports from facilities like the Mayo Clinic. Accidental ingestion can cause gastrointestinal distress, while exposure to the tympanic membrane or meninges can cause ototoxicity or chemical meningitis. Its use in neonatal intensive care units is carefully monitored due to potential skin irritation risks.

History and society

Chlorhexidine was first synthesized in 1946 by scientists at Imperial Chemical Industries in the United Kingdom. Its development was part of a broader post-World War II effort to find novel antimicrobials, paralleling the discovery of penicillin. It was introduced into clinical practice in the 1950s and gained prominence following landmark studies, such as those published in *The Lancet*, demonstrating its superiority over povidone-iodine for skin antisepsis. Its inclusion in the WHO Model List of Essential Medicines underscores its global health importance.

Research and other applications

Ongoing clinical trials, often registered with ClinicalTrials.gov, investigate its role in reducing surgical site infection rates in procedures like cesarean section and orthopedic surgery. Research explores its efficacy against emerging pathogens, including methicillin-resistant Staphylococcus aureus in community settings. Beyond human medicine, it is used in veterinary surgery and as a disinfectant in the food industry, sanctioned by agencies like the Food and Drug Administration. Novel formulations, such as chlorhexidine-impregnated sutures and central line dressings, are subjects of patents held by corporations like 3M and Johnson & Johnson. Category:Antiseptics Category:Biguanides Category:World Health Organization essential medicines