**Pharmaceutical Chemistry: Lesson 21: Antiseptics**

I. Definition:

Antiseptics are chemical substances that have the ability to kill or inhibit the growth of bacteria, fungi, viruses, and other microorganisms on surfaces, instruments, or the human body.

II. Mechanism of Action of Antiseptics:

• On the cytoplasm:

• Cause leakage of small molecules like K+, amino acids, and purines.

• Induce irreversible aggregation of larger molecules like nucleic acids and proteins.

• Inactivate enzymes.

• On the bacterial surface:

• Bind to cations on the outer membrane of Gram-positive bacteria.

• Release polyliposaccharides.

• Lyse cells.

• Affect metabolic processes.

III. Properties of a Good Antiseptic:

• Broad spectrum: Effective against a wide range of bacteria.

• Active in the presence of organic matter: (blood, serum, pus…)

• Stable upon dilution: Activity is not significantly reduced when diluted.

• Well-tolerated locally, non-toxic to the body: Does not cause irritation, allergies, or toxicity when used.

IV. Classification of Antiseptics:

1. Inorganic Antiseptics:

• Oxidizing agents:

• Hydrogen peroxide (H2O2):

• Preparation:

• Electrolysis of sulfuric acid.

• Oxidation of quinones.

• Classification:

• Dilute 3% equivalent to 10 volumes (10V).

• Concentrated 30% equivalent to 100 volumes (100V).

• Indications:

• Mild antibacterial action, hemostatic.

• Has a mechanical effect of bubbling (oxygen) when cleaning wounds.

• Note:

• Solutions above 20 volumes are corrosive to the skin and must be diluted for use.

• Potassium permanganate (KMnO4):

• Uses:

• Disinfecting wounds.

• Sterilizing instruments.

• Note:

• A strong oxidizing agent, it can cause skin irritation.

• Halogens:

• Chlorine:

• Chlorine-releasing agents:

• N-chlorosulfonamide.

• Chloramine T.

• Dichloramine T.

• Halazone.

• Uses:

• Disinfecting skin, mucous membranes, cleaning wounds, burns.

• Use chlorine preparations containing 0.5% active chlorine.

• Note:

• Mycobacteria show resistance; higher concentrations (10 times) are required.

• Preparation:

• Bubbling chlorine gas through NaOH solution.

• Electrolysis of NaCl solution without a diaphragm.

• Mechanism of action:

• HClO is more active than ClO− (4–10 times) due to its ability to diffuse through bacterial membranes.

• The ratio of Cl2 : HClO : OCl− depends on the pH of the medium.

• Determination of active chlorine:

• The amount of chlorine corresponds to the amount of iodine that can be titrated with sodium thiosulfate in the presence of potassium iodide in an acetic acid medium.

• Chlorine content:

• British chlorine content (% chlorine): The number of grams of chlorine released from 100 g of the product.

• French chlorine content (Gay Lussac chlorine content): The number of liters of chlorine gas (at 0 °C, 760 mmHg) released from 1 kg or 1 L of liquid product.

• Iodine:

• Uses:

• Disinfecting skin, wounds.

• Note:

• Should not be combined with mercury salts due to the formation of skin-corrosive substances.

• Preparations:

• POLYVINYL PYROLIDONE IODINE (PVP IODINE):

• Solutions of this compound are much more stable than iodine alcohol or Lugol’s solution.

• A stable complex of iodine and polymer with free iodine (10%) and a complex.

• Heavy metals:

• Silver salts:

• Mechanism of action:

• Bind to bacterial proteins, inhibit enzymes, prevent DNA recombination.

• Ag+ interacts with thiol groups (-SH) present in amino acids like cysteine, disrupting hydrogen bonds in protein structures.

• Ag+ interacts with base pairs in DNA.

• Organic silver salts:

• Silver sulfadiazine: slowly releases Ag+ into the wound. Dosage form: Cream.

• Mercury salts:

• Mechanism of action: Bind to -SH (thiol), -COOH (carboxyl), -OH (hydroxyl), -PO4 3- (phosphate) groups of bacterial enzymes, causing inactivation.

• Uses:

• 2% mercury salt solution in water for skin disinfection.

• Note:

• Highly toxic, must be used with caution.

• Should not be combined with iodine.

2. Organic Antiseptics:

• Alcohols:

• Which type of alcohol has the strongest antiseptic activity? Primary alcohols.

• Commonly used alcohols for antiseptic purposes:

• Ethanol.

• N-propanol.

• Isopropanol.

• Activity increases with increasing carbon chain length.

• Mechanism of action:

• Straight chain: Protein + enzyme denaturation => bacterial and fungal killing, but not spore killing.

• Aromatic alcohols: Alter permeability + protein coagulation.

• Note:

• Alcohols are ineffective against bacterial spores.

• Phenols and derivatives:

• Mechanism of action:

• Low concentrations: Damage cell membranes, leak cell contents, inactivate enzymes.

• High concentrations: Coagulate proteins.

• Note:

• Phenol causes keratin precipitation, leading to skin necrosis.

• Aldehydes:

• Formaldehyde:

• Uses: Disinfecting medical instruments, preserving biological specimens.

• Dosage form: Solution containing 30–40% formaldehyde.

• Note:

• Preparations contain methanol to prevent formaldehyde polymerization.

• Highly toxic, must be used with caution.

• Amines:

• Methenamine (Urotropin):

• Uses: Disinfecting the urinary tract by releasing formaldehyde in the kidneys.

• Biguanides:

• Chlorhexidine dihydrate:

• Uses: Most widely used antiseptic, especially in oral care products, hand washing.

• Dosage form:

• 0.05% aqueous solution containing chlorhexidine dihydrate: HIBIDIL for wound cleaning.

• 4% aqueous solution containing chlorhexidine dihydrate: HIBICRUB for hand washing.

• 0.5% water-alcohol solution containing chlorhexidine dihydrate: HIBITANE for surgical areas.

• Note:

• Reduced activity when exposed to blood, pus.

• Inactivated by anionic surfactants.

• Dyes:

• Crystal violet.

• Methylene blue.

• Proflavine.

• Action: Bacteriostatic against Gram-positive organisms.

• Acids:

• Benzoic acid: Used in cosmetics as a bacteriostatic and fungistatic agent.

• Nalidixic acid: Used in combination with antibiotics for urinary tract infections.

V. Precautions When Using Antiseptics:

• Choose the right antiseptic for the type of bacteria, fungi, or virus to be killed.

• Strictly follow the dosage, duration, and method of use stated on the packaging.

• Use caution when handling corrosive or toxic antiseptics.

• Wash your hands thoroughly after using antiseptics.

• Store antiseptics in a dry, cool place, away from direct sunlight.

VI. Antiseptics Used Orally to Treat Urinary Tract Infections:

• Methylene blue: Bacteriostatic action against Gram-positive organisms.

• Methenamine (Urotropin): Releases formaldehyde in the kidneys.

• Nalidixic acid: Used in combination with antibiotics for urinary tract infections.

VII. Additional Information:

• Which component of Dakin’s solution plays a role in limiting the decomposition of NaClO? NaHCO3.

• Volume of oxygen gas released from 1 liter of concentrated hydrogen peroxide solution: 100 liters.

• The trifluorocarbon group -CF3 is used as a replacement for the chloro group because they have similar sizes.

VIII. Conclusion:

Antiseptics are crucial chemical substances in controlling and preventing infections. The rational and safe use of antiseptics helps protect human health and limit the spread of diseases.