Benzalkonium chloride (BAC) was first synthesized in the early 20th century during the broader exploration of quaternary ammonium compounds. Its strong antimicrobial properties were identified through laboratory observations, and in 1935, German pathologist Gerhard Domagk was the first to report its disinfectant capabilities. This discovery paved the way for its public use as an antiseptic and disinfectant. Benzalkonium chloride (BKC) is a quaternary ammonium compound commonly used as an antiseptic, disinfectant, and preservative, thanks to its broad-spectrum antimicrobial activity. Acting as a cationic surfactant, it effectively eliminates bacteria, fungi, and enveloped viruses, while also inhibiting the growth of other microorganisms. BKC is frequently found in products like disinfectants, hand sanitizers, antiseptic wipes, and contact lens solutions.
BRAND NAMES
Bactine: A first-aid liquid that uses benzalkonium chloride as an antiseptic to prevent infection and lidocaine as a topical anesthetic to relieve pain and itching.
Tanac and Orajel: Brands that use benzalkonium chloride for treating cold sores and other minor skin conditions.
Zephiran: A brand of benzalkonium chloride used as a surface-acting agent and antiseptic.
MECHANISM OF ACTION
Benzalkonium chloride primarily works by disrupting microbial cell membranes, leading to leakage of cellular contents and ultimately cell death. As a cationic surfactant, it binds to negatively charged microbial membranes through electrostatic interactions and integrates into the lipid bilayer, causing structural damage. This destabilization compromises membrane integrity, allowing essential components to leak out, and may also interfere with intracellular enzymes and metabolic functions.
PHARMACOKINETICS
Absorption
Benzalkonium chloride (BAC) has low systemic absorption when applied topically, primarily due to its large, positively charged molecular structure. However, it can be adsorbed by materials such as soft contact lenses, filter membranes, and activated carbon. In consumer products, systemic exposure remains minimal, with adsorption largely influenced by the chemical properties of the material it interacts with.
Distribution
There is no standard "volume of distribution" for benzalkonium chloride (BAC) because it varies significantly based on its formulation, concentration, and how it's delivered.
Metabolism
Benzalkonium chloride (BAC) is primarily metabolized in the liver by cytochrome P450 (CYP) enzymes, which oxidize the alkyl chain. Metabolism serves as a detoxification pathway by making the compound less potent and easier to excrete from the body.
Excretion
Benzalkonium chloride is poorly absorbed and, when absorbed, is mainly metabolized in the liver and excreted in bile, with a small amount eliminated unchanged in urine.
PHARMACODYNAMICS
The pharmacodynamics of benzalkonium chloride involve its role as a cationic surfactant that targets microbial cell membranes. It binds to negatively charged phospholipids, disrupting membrane integrity and causing leakage of cellular contents, ultimately leading to bacterial cell lysis.
DOSAGE AND ADMINISTRATION
Topical antiseptics: Typically used in concentrations of 0.1% to 0.13%. Apply directly to the skin; avoid contact with eyes unless specified.
Ophthalmic (eye drops): Used at 0.004% to 0.02%. Administer 1–2 drops as directed, avoiding prolonged use due to potential irritation.
Nasal sprays: Usually contain 0.01% to 0.05%. Use as recommended, typically 1–2 sprays per nostril.
Disinfectants (for surfaces): Commonly used in 0.05% to 0.2% concentrations. Apply to surfaces and allow contact for several minutes before wiping.
Hand sanitizers and antiseptic wipes: Contain 0.1% to 0.13% BAC. Use as needed on hands or small skin areas.
Contact lens solutions: Contain very low concentrations (0.004% to 0.01%); use only as directed for lens cleaning.
FOOD INTERACTIONS
Benzalkonium chloride (BAC) has no known significant food interactions when used as a topical or ophthalmic antiseptic. However, certain products containing BAC may advise avoiding food or drink for a short time after use to ensure optimal effectiveness. It’s always advisable to consult a doctor or pharmacist, especially if you're using BAC-containing products alongside other medications, supplements, or have underlying health conditions.
DRUG INTERACTIONS
Benzalkonium chloride (BAC) has minimal systemic interactions but can increase local irritation when combined with other topical products. In eye drops, it may affect absorption or cause irritation, especially with other eye medications. BAC can also bind to soft contact lenses, potentially causing irritation. Always consult a healthcare professional before combining BAC with other treatments.
CONTRAINDICATIONS
The main contraindication for benzalkonium chloride (BAK) is a known allergy or hypersensitivity to BAK or other quaternary ammonium compounds. Additional precautions or contraindications may apply depending on the specific use and the patient's condition.
SIDE EFFECTS
Irritation.
Contact dermatitis.
Allergic reactions.
Dry eye.
Ocular surface disease.
Inflammation and fibrosis.
Nasal irritation.
Asthma.
Bronchospasm.
Serious injury from ingestion.
Nausea and vomiting.
OVERDOSE
Nausea.
vomiting.
abdominal pain.
Burning or irritation of the mouth, throat, or skin.
Difficulty breathing (if ingested or inhaled in large amounts).
Hypotension.
CNS depression.
coma in severe cases.
TOXICITY
Benzalkonium chloride (BAC) toxicity is primarily associated with exposure to concentrated solutions or accidental ingestion. It can cause irritation and chemical burns to the skin, eyes, and mucous membranes. Ingestion may lead to nausea, vomiting, abdominal pain, and, in severe cases, respiratory distress or central nervous system depression. Prolonged or repeated exposure to lower concentrations may also cause skin sensitization or allergic reactions. Systemic toxicity is rare due to poor absorption, but severe cases require prompt medical attention and supportive care, as there is no specific antidote.
