midterms

• Germicides

  Anti-infective agents used locally
• Antiseptic


  Anti-infective agent that is static/-cidal when applied on living tissue
• Disinfectant

  Agent that prevents transmission of infection when applied on inanimate objects
• Hand washing is the most important means of preventing transmission of infectious agents
• Alcohols

  Mechanism of action: Denaturation of protein and carbohydrates
• Ethanol


  • Clear colorless volatile liquid with a burning taste and pleasant odor
  • Commercial C2H5OH; 95% ethanol by volume
  • Fermentation product from grain and many other carbohydrates
  • Synthetically prepared by H2SO4 – catalysed hydration of Ethylene
  • Accepted conc.: 160 proof or more/ 70% alcohol
• Denatured alcohol


  Rendered unfit for use in intoxicating beverages
• Completely denatured alcohol

  Contains methanol and benzene
• Specially denatured alcohol


  Ethanol treated with one or more substances for a specialized purpose, e.g. Iodine tincture, Mouthwashes, Aftershave lotions
• Primary use of ethanol

  • External antiseptic, preservative, mild counterirritant or solvent
  • Rubbing Alcohol: astringent, rubefacient, and a mild local anaesthetic
• Metabolism of ethanol

  • Series of Oxidation
  • Alcohol dehydrogenase
  • Acetaldehyde: causes N&V, vasodilatory flushing
  • Disulfiram: Aversion therapy; blocks Alcohol dehydrogenase
  • Aldehyde dehydrogenase
  • Ethanoic acid
• Dehydrated ethanol

  • Absolute alcohol/ 99% w/w C2H5OH
  • Prepared by azeotropic distillation of an ethanol-benzene mixture
  • Very high affinity with water; stored in a tightly-sealed container
  • Uses: Chemical reagents, Local relief for pain in carcinomas & neuralgias
• Isopropyl alcohol

  • Isopropanol/2-propanol
  • Colorless, volatile liquid with slightly bitter taste and a characteristic odor
  • Substitute for ethanol
  • Synthetically prepared by H2SO4 – catalysed hydration of Propylene
  • Uses: Disinfectant for surgical instruments, Rapidly bactericidial (50% - 95% conc.), Antiseptic (40% conc.), Pharmaceuticals & toiletries as solvents & preservatives
• Ethylene oxide

  • C2H3OH; colorless, flammable gas that liquefies at 12oC
  • Uses: Sterilant for temperature-sensitive medical equipment & certain pharmaceuticals that cannot be heat sterilized in an autoclave, Carboxide (10% ethylene oxide and 90% carbon dioxide by volume)
• Formaldehyde solution

  • Formalin
  • Colorless & pungent aqueous solution
  • Officially contains not less than 37% w/v of H2CO, with methanol added to retard polymerization
  • Mechanism of action: slow but powerful; direct, nonspecific alkylation of nucleophilic functional groups in proteins and nucleic acids to form carbinol derivatives
  • Hardens the skin, irritating to mucous membranes, causes GI distress, and is common for contact dermatitis
  • Carcinogenic
• Glutaraldehyde disinfectant solution

  • Cidex
  • A 5-carbon dialdehyde
  • Use: Sterilant
  • Stabilized in alkaline solution
  • Two components: Glutaraldehyde (2%) and Buffer (pH 7.5 – 8.0)
  • Non-buffered are acidic, stable but lack sporicidal activity
• Phenols

  Mechanism of action: Low conc: PROTEIN DENATURATION, High conc: LYSIS OF CELL MEMBRANE
• Phenol coefficient


  The ratio of a dilution of a given test disinfectant to the dilution of phenol that is required to kill a strain of S. typhi under carefully controlled time and temperature conditions
• Phenol

  • Carbolic acid
  • characteristic: Colorless to pale –pink crystalline material with "medicinal odor"
  • Soluble in water, methanol, salol, and very soluble in alcohol
  • General protoplasmic poison: germicidal activity
  • Caustic to the skin
  • Uses: Local anesthetic – diluted form, Anti-pruritic – Phenolated calamine (0.1-1%), Cauterize wounds – 4% in glycerine
• Liquefied phenol

  • Phenol with 10% water
  • Water content precludes its use in fixed oils or liquid petrolatum
  • Not miscible with lipophilic ointment bases
• Chlorophenol


  • Used in combination with camphor in liquid petrolatum
  • Uses: External antiseptic, Anti-irritant
• 1. Chloro-m-xylenol

  • PC-MX; Metasep
  • Non-irritating antiseptic agent
  • Uses: Anti-fungal, Anti-bacterial, Treatment for athlete's foot & jock itch, Marketed in 2% conc. as shampoo
• Hexachlorophene

  • 2,2' –methylenebis (3,4,6-tricholorophenol), 2,2'-dihydroxy-3,5,6,3'5', 6'-hexachlorodiphenylmethane
  • Insoluble in water, soluble in alcohol
  • Easily absorbed onto the skin and enters sebaceous glands
  • Uses: Topical applications, 2 – 3% in soaps, detergent creams, lotions, and shampoos for antiseptic use
  • Systemically toxic (oral & IV admin.), Neurotoxic in infants
• Cresol

  • Mixture of three isomeric methylphenols
  • Obtained from coal tar or petroleum by alkaline extraction into aqueous medium, acidification, and fractional distillation
  • Inexpensive antiseptic & disinfectant
  • Sparingly soluble in H2O
  • Drawback: UNPLEASANT ODOR
• Chlorocresol

  • 4-chloro-3-methylcresol
  • Colorless crystals, slightly soluble in water
  • Used only as preservative
• Thymol

  • Isopropyl m-cresol
  • From Thymus vulgaris by partitioning into alkaline aqueous medium followed by acidification
  • Slightly soluble in water
  • Uses: Mild fungicide, Dusting powders for tinea infections
• Eugenol

  • 4-allyl-2-methoxyphenol
  • Obtained from clove oil
  • Pale-yellow liquid with strong aroma of cloves and pungent taste slightly soluble in H2O but miscible in alcohol and other organic solvents
  • Uses: Toothache drops, Local anaesthetic, Antiseptic, Used in mouthwashes
• Resorcinol

  • m-dihydroxybenzene (resorcin)
  • Occurs as white needles or amorphous powder that is soluble in water & alcohol & light sensitive
  • Weak antiseptic
  • Uses: 1 – 3 % antiseptic solution, 10 – 20% in skin conditions such as ringworm, eczema, psoriasis, and seborrheic dermatitis, Keratolytic & Antifungal
• Hexylresorcinol


  • Numb the tongue
  • Used in lozenges as local anaesthetic, not antiseptic
• Oxidizing agents

  • Germicidal activity depends on the ability to liberate oxygen in the tissues
  • Many are inorganic compounds: Hydrogen peroxide, Sodium perborate, Metal peroxides, Potassium permanganate
  • Generate oxygen and free radicals
  • Effective against anaerobic microbes
  • Drawbacks: Limited effectiveness; poor penetrability, Oxidation is transient
• Carbamide peroxide topical solution

  • Gly-Oxide
  • Stable complex of urea and hydrogen peroxide (H2NCONH2 H2O2)
  • 12.6% carbamide peroxide in anhydrous glycerine
  • Uses: Antiseptic, Disinfectant, Treatment for oral ulcers, Used in dental care
• Hydrous benzoyl peroxide

  • Oxy-5, Oxy-10, Vanoxide
  • White granular powder
  • Pure form is explosive
  • Formulated with 30% water to make it safer to handle
  • 5-10% conc: Keratolytic, Keratogenic, Treats acne
• Iodophores

  • Elemental iodine: oldest germicide still in use today
  • Iodine tincture: 2% iodine in 50% alcohol with sodium iodide
  • Strong iodine solution: Lugol's solution; 5% iodine in water with KI
  • Iodine solution: 2% iodine in Sodium iodide
  • Have both bactericidal & fungicidal properties
• Povidone-iodine

  • Betadine, Isodine, PVP-iodine
  • Non-toxic, non-volatile, and nonstaining form of iodine
  • 10% of the iodine in the complex is bioavailable
  • Uses: for post-surgical disinfection of the incision site, effective for local bacterial and fungal infections
• Chlorine-containing compounds

  • Used in disinfection of water supplies
  • Hypochlorous acid when dissolved in water were developed as disinfectant
  • Mechanism of action: chlorination of amide nitrogen atom, oxidation of sulfhydryl groups in proteins
• Halazone

  • p-dichlorosulfamoylbenzoic acid
  • A white, crystalline, photosensitive compound with faint chlorine odor
  • Sodium salt is used to disinfect drinking water
• Chloroazodin

  • N,N-dichlorodicarbonamidine, Azochloramid
  • A bright yellow crystalline solid mostly insoluble in water and unstable in light or heat
  • Explodes if heated above 155oC
  • Uses: Dilute solutions to disinfect wounds, As packing for dental carries, For lavage and irrigation
  • Action is long lasting
• Oxychlorosene sodium

  • Chlorpactin: complex of the sodium salt of dodecylbenzenesulfonic acid and hypochlorous acid
  • Occurs in white amorphous powder with a faint odor of chlorine
  • Uses: To treat localized infections to remove necrotic tissue, counteract odor
• Halazone

  1. dichlorosulfamoylbenzoic acid, a white, crystalline, photosensitive compound with faint chlorine odor
• Halazone

  Sodium salt is used to disinfect drinking water