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Natural or synthetic originated chemical substances, which are used for curing diseases are known as medicines or drugs and the branch of chemistry related to the treatment of diseases by using suitable chemicals is called chemotherapy.

There is a little difference between drugs and medicines.

"A medicine is a chemical substance which cures a certain disease and safe to use due to negligible toxicity and does not cause addiction. However a drug is a chemical substance which also cures the disease but is habit forming, cause addition with serious side effects."

For example, penicillin and heroin both are medicines as penicillin is an effective antibacterial agent and heroin is a pain killer.
But penicillin is a medicine with no side effect and heroin is a drug due to its addictive property.

Drugs show side effect because of their property to bind up with more than one type of receptors.
This interaction can form some biologically active degradation products which can interact with other receptors.

Drugs can be many types like

  1. Antacids: they can neutralize the excess acid and increase the pH to an appropriate level in stomach. For example; Cimetidine, Ranitidine (Alb) (Zydus).
  2. Antihistamines: These drugs interfere with the natural action of histamine. For example, Brompheniramine.
  3. Neurologically active drugs: These drugs impart effect on the message transfer process from nerve to receptor. For example, Tranquillizer (lponiazid) and Analgesics (Aspirin).
  4. Antimicrobial: Used for the curing process of diseases caused by microbes and other microorganism. For example, Salvassan, Sulphanilamide.
  5. Antibiotic: Drugs which used for either kill or inhibit the growth of microorganisms. For example, Tetracycline.
  6. Antiseptic and disinfectant: Prevent the growth of microorganism. For example, Chloroxylenol, Bithional.
  7. Antifertility drugs: used in birth controlled piles or oral contraceptives. For example, Mifepristone.


Types of Disinfectant

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The chemical substances which are kill microorganism but are not safe to apply on living tissues. They are generally used to kill the microorganism present in the drains, toilets and floor etc.

Generally the same substance can act as antiseptic as well as disinfectant which depend upon the concentration of solution used. Low concentration of substance makes solution antiseptic while the chemical substance present in high concentration in disinfectant. The activity of disinfectant depends on the concentration of solution, pH of system as well as on the contact time with surface.

Disinfectants classified on the basis of their activity and their chemical structure. Some common types of disinfectants are as follow.

Phenolic disinfectant
  • Phenolic compounds and their derivative are present as active ingredients in many household disinfectants, mouthwashes and in soap and hand washes.
  • Some common phenolic compounds used as disinfectant are phenol, o-Phenylphenol, Chloroxylenol, Hexachlorophene, Thymol, Amylmetacresol.
  • Out of all these compounds, phenol is the oldest disinfect used for several purpose.
  • Due to corrosive nature and sensitivity of some people with phenol, the substituent of phenol, o-Phenylphenol is used instead of that.
  • Other compounds like Chloro-xylenol used in preparation of dettol and Amylmetacresol is present in strepsils used for throat disinfection.
  • Triclosan is also a phenolic compound which is an active ingredient in antibacterial soaps and detergents.
Alcoholic disinfectant
  • Many alcohols like ethanol, isopropanol are good disinfectants and effectively kill fungi and bacteria.
  • The main disadvantage of this disinfectant is that they cannot kill endospores and non-enveloped viruses.
  • These disinfectants denatured the protein cover of microorgamism and dissolve the lipids from the lipid envelop of viruses.
Air disinfectants
  • Chemical substances which are capable to disinfect microorganism suspended in air.
  • Air disinfectants are dispersed either as an aerosol or vapour at a sufficient concentration in the air and used reduce the concentration of viable infectious microorganisms.
  • Some common disinfectants are glycol, propylene glycol, triethylene glycol.
  • Surface-active agents like soaps, detergents, wetting agents are also good disinfectants.
  • These chemical substances act against gram positive bacteria, fungi, protozoa, some viruses while weak against gram negative bacteria or spores.
  • Halogens like iodine, chlorine very common disinfectant.
  • For example, iodine is the oldest and most effective antiseptic with the capability of impair the protein synthesis and affect the cell membranes.
  • Iodine can be used for in aqueous form or in the form of solution with alcohol.
Quaternary ammonium compounds
  • Some quaternary ammonium compounds like benzalkonium chloride act as good disinfectant.
  • They have capability to kill algae, hence can also be used as an additive in large-scale industrial water systems to minimize undesired biological growth.
  • Many aldehydes like formaldehyde, ortho-phthalaldehyde , Pentane-1,5-dial (glutaraldehyde) act as disinfectant.
  • They act on fungi and are good sporocidal.
Oxidizing agent
  • Some oxidizing agents like hydrogen peroxide, chloramine, chlorine dioxide, ozone, peracetic acid, sodium hypochlorite, Potassium permanganate, calcium hypochlorite, performic acid and Potassium peroxymonosulfate are also good disinfectant.
  • For example bleach is a solution of sodium hypochlorite and calcium hypochlorite is a swimming pool additive.
  • Chloramine, chlorine dioxide and ozone are used for the disinfection of drinking water.

Different disinfectants show differ activity for various microorganism. Some microorganism with their activity towards disinfectants is as follows.

Toxicity Against Disinfectant
Phenolic Compounds Hypochlorites Alcohols Formaldehyde Glutaral Iodophors
Fungi good medium nil good good good
Bacteria (gram +/-) good good good good good good
Mycobacteria fair fair good good good good
Spores nil fair nil good good medium
Lipid Viruses medium medium medium medium medium medium
Non-Lipid Viruses variable medium variable medium medium medium
Skin medium medium nil medium medium medium
Eyes medium medium medium medium medium medium
Lungs nil medium nil medium medium nil

Natural Disinfectants

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There are many chemical substances used as disinfectants. With these all chemical substances, there are many inexpensive, easy-to-use natural alternatives disinfectants. These natural substances can safely be used in place of chemical substances. These natural substances are quite safe to use and easy to handle compare to chemical substances.

Some natural disinfectants are as follows.
  1. Sodium bicarbonate (NaHCO3)- Also called as baking Soda which widely used for cleaning, deodorizes and for making water soft.
  2. Soap- They are sodium and potassium salts of fatty acids. Soaps are used either in the form of liquid, flakes or powders. They are biodegradable and good disinfectants.
  3. Lemon- Lemon and other citrus fruits contain citric acid which is a good disinfectant and quite effective on almost all household bacteria.
  4. Sodium borate- Also called as borax and is widely used as cleanser, deodorizes, disinfects and for softens the water. It can also used for cleaning the wallpaper, painted walls and floors.
  5. White Vinegar- It is a dilute solution of acetic acid and used to remove grease stains and odours.
  6. Washing Soda- It is sodium carbonate decahydrate (Na2CO3.10H2O) also named as SAL Soda.
  7. Isopropyl Alcohol- Like ethanol it also acts as disinfectant but it is better than ethanol in action against microorganisms.
  8. Cornstarch- can be used for cleaning windows, polishing the furniture, shampoo carpets and rugs.
  9. Citrus Solvent- Like lemon juice, citrus solvent also used for cleans paint brushes and also worked on some stains.
All-natural apple cider vinegar is very effective on bacteria. They are preventing the growth of bacteria and acts as good disinfectants. Some essential oils like lavender and clove oil are used to increase the disinfecting properties of the cleanser and also for a pleasant aroma. The presence of pine oil in cleaning products makes it excellent disinfectants.

Examples of Disinfectants

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Some common examples of disinfectants are as follow.
  • 0.2 to 0.4 ppm solution of chlorine is used for sterilization of water toi make it useful for drinking purpose.
  • Dettol is act as an antiseptic as well as disinfectant used for floor cleaner and infected clothes.
  • The solution of chlorhexidine gluconate (savlon) also acts as a good disinfectant in suitable solvent.
  • An antiseptic; Bithional is added to good quality of soaps to reduce the odours produced by bacterial decomposition of organic matter on the skin.
  • Iodoform and 2-3% solution of iodine in water and alcohol is called as tincture which is a very good antiseptic and disinfectant.
  • The dilute aqueous solution of boric acid and borax is also used as disinfectant.
  • A solution of cresols (ortho, meta and para) in soapy water is called as Lysol and used as disinfectant.
  • Silver and silver compounds like silver dihydrogen citrate (SDC) also acts as disinfectant by killing the microorganism through the deactivation of structural and metabolic membrane proteins of microorganism.
  • Some metal alloys also act as disinfectant and have ability to destroy a wide range of microorganism like Copper-alloy.
  • High intensity, low wave length ultra violet radiations are also a good disinfectant for smooth surface like dental tools.
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