Miscellaneous Drugs Notes

Chelating Agents

Chelating agents combine with metallic ions and form ring structures that are water-soluble complexes and are rapidly excreted from the body. These agents are used in heavy metal poisoning. Various chelating agents are as follows:

1. Dimercaprol (British anti-Lewisite [BAL])
2. Disodium edetate (Na₂EDTA)
3. Calcium disodium edetate (CaNa₂EDTA)
4. d-Penicillamine
5. Desferrioxamine
6. Deferiprone

Read And Learn More: Pharmacology for Dentistry Notes

• Summary of Chelating Agents

An ideal chelating agent should

1. Be highly water soluble,
2. Be neither metabolized nor stored in the body,
3. Be readily excreted in urine and
4. Have a low affinity for calcium.

Dimercaprol

It was developed as an antidote for arsenic-containing war gases such as lewisite during World War 2. The sulfhydryl (SH) groups of dimercaprol (BAL) react with metals to form a chelating complex. It is used in arsenic, mercury, gold, and bismuth poisoning; also as an adjuvant in copper and lead poisoning.

• Adverse effects:
  • Nausea, vomiting, headache, fever, salivation, rise in BP, tachycardia, and pain at the site of injection.

Disodium Edetate

On intravenous (i.v.) administration, it chelates calcium and causes hypocalcaemic tetany. Hence, it is not preferred in lead poisoning. It can be used in the treatment of hypercalcemia and as an anticoagulant in vitro.

Calcium Disodium Edetate

It is preferred in the treatment of lead poisoning, as it does not deplete calcium. Calcium in the chelating agent is exchanged with heavy metal. It can also be used in zinc, copper, and manganese poisoning. It is administered intravenously or intramuscularly. In dentistry:

1. EDTA forms a complex with calcium in the dentin; hence, manipulation of dentin by instrumentation becomes easier.
2. It is used as a final rinse for cleaning the root canal to remove the smear layer from the canal wall.
   • Adverse effects:
     • Calcium EDTA is toxic to kidneys. The other side effects are fatigue, fever, myalgia, headache, nausea, vomiting, etc.

d-Penicillamine

It is a degradation product of penicillin; hence, it may have cross-reactivity with penicillin. It is effective in copper, mercury, zinc, and lead poisoning. Other uses are Wilson’s disease and rheumatoid arthritis.

• Adverse effects: Skin rashes, pruritus, urticaria, pyrexia, etc.

Desferrioxamine (Deferoxamine)

It is an iron-chelating agent. It is not effective orally, as it is poorly absorbed from the GI tract. It is administered parenterally (i.m./i.v.). It is used for treating acute and chronic iron poisoning.

• Adverse effects include allergic reactions such as skin rashes, itching, flushing, and anaphylaxis. Other adverse effects are diarrhea, dysuria, hypotension, and tachycardia

Deferiprone

It is an orally effective iron-chelating agent. It is used in the treatment of transfusion siderosis in thalassemia and also in acute iron poisoning.

• Adverse effects: They are anorexia, nausea, vomiting, joint pain, and rarely agranulocytosis.

Antiseptics And Disinfectants

1. Sterilization: It is the destruction of all microorganisms including spores.
2. Germicide: It is an agent used to kill microorganisms but not spores. It includes disinfectants and antiseptics.
3. Disinfectant: It is an agent used to eliminate microorganisms on inanimate objects.
4. Antiseptic: It is an agent used to eliminate microorganisms in living tissues.

Classification

1. Phenols and related agents: Phenol, cresol, chlorhexidine, resorcinol, hexachlorophene, chloroxylenol.
2. Alcohols: Ethyl alcohol, isopropyl alcohol.
3. Aldehydes: Formaldehyde, glutaraldehyde.
4. Oxidizing agents: Hydrogen peroxide, potassium permanganate.
5. Halogens, halogen-releasing agents: Chlorine, sodium hypochlorite, iodine, iodophors.
6. Acids: Benzoic acid, boric acid.
7. Metallic salts: Silver nitrate, zinc sulfate.
8. Dyes: Gentian violet, brilliant green, methylene blue.
9. Surface-active agents (detergents): Common soaps, cetrimide, benzalkonium chloride, cetylpyridinium chloride.
10. Gases: Ethylene oxide, β-propiolactone.

Mnemonic for classification: ‘PHARMA GOD’.

• Phenols
• Halogens
• Alcohols, Aldehydes
• SuRface-active agents
• Metallic salts, Miscellaneous
• Acids
• Gases
• Oxidizing agents
• Dyes

An ideal antiseptic

1. Should be effective against all pathogens
2. Should be effective in the presence of organic matter like blood, pus, and excreta.
3. Should be cheap and stable.
4. Should not cause irritation on topical application.

Phenols And Related Agents

They are protoplasmic poisons. They disrupt the cell wall.

1. Phenol (carbolic acid)
   • Rarely used as an antiseptic, as it is corrosive and can penetrate intact skin.
   • Used to disinfect sputum, pus, excreta, and discarded cultures.
   • Accidental or suicidal ingestion can cause corrosion of the gastrointestinal tract (GIT), convulsions, hypothermia, and collapse. Treatment is symptomatic.
2. Cresol (methyl phenol)
   • More active and safer than phenol.
   • Used to disinfect utensils, excreta, and infected glassware.
3. Triclosan
   • Nonirritating and nonstaining.
   • Component of mouthwash – used in gingivitis, and bad breath.
4. Chloroxylenol
   • The active ingredient of Dettol.
   • Less toxic than phenol.
   • Used to disinfect surgical instruments and as an antiseptic for skin before any surgery.
5. Resorcinol
   • Nonstaining and less toxic.
   • It has keratolytic and antipruritic properties; hence used in eczema, ringworm, and seborrhoeic dermatitis.
6. Hexachlorophene
   • Chlorinated phenol.
   • Greater than 2% solution is not used.
   • Used as an antiseptic for skin before surgery, furunculosis, and seborrhoeic dermatitis.
7. Chlorhexidine
   • Used as an antiseptic for skin prior to surgery.
   • As an antiseptic in mouth rinse, it is used as an antiplaque and antigingivitis agent.
   • Taste alteration and staining of the oral cavity are the common side effects.

Alcohols

They act by denaturing bacterial proteins and precipitating them.

1. Ethyl alcohol
   • 70% ethyl alcohol is used as an antiseptic on the skin before injections and surgical procedures. Its antiseptic efficacy decreases above 90%.
   • It should not be used on open wounds, mucosa, ulcers, and scrotum, as it is highly irritant.
   • Not useful for disinfecting instruments as it promotes rusting.
2. Isopropyl alcohol
   • More potent.
   • 68%–72% is used as an antiseptic.
   • Can be used to disinfect clinical thermometers.

Aldehydes

They act by denaturing the proteins. They are protoplasmic poisons.

1. Formaldehyde
   • 40% solution is called formalin.
   • Formaldehyde solution is used for disinfection of sputum, removal of warts on palms and soles, to treat hyperhidrosis, and preservation of anatomical and pathological specimens.
   • Formaldehyde gas is used for the fumigation of wards and operation theatres; rarely, for sterilization of heat-sensitive instruments and gloves.
   • In dentistry, it is used to harden the residual pulp tissue.
2. Glutaraldehyde
   • Preferred over formaldehyde to sterilize surgical instruments, plastic endotracheal tubes, face masks, corrugated rubber tubes, endoscopes, respirators thermometers, etc.
   • 2% solution is used to sterilize endodontic instruments in dentistry.

Oxidizing Agents

They act by releasing nascent oxygen which oxidizes the bacterial protoplasm.

1. Hydrogen peroxide
   • Colorless liquid.
   • Effervescence is seen when applied to tissues due to the presence of the enzyme catalase, which degrades hydrogen peroxide.
   • Used for cleaning wounds and abscess cavities, removal of the slough, and ear wax.
   • Can also be used to disinfect contact lenses, plastic implants, and surgical prostheses.
   • In dentistry, it is used as a mouthwash and to disinfect septic sockets and root canals.
2. Potassium permanganate
   • Dark purple crystals that are water-soluble.
   • Condy’s lotion is a 1:4000–1:10,000 solution of potassium permanganate. It is used for gargling.
   • 5% solution is used as a styptic
   • 1% solution is used for fungal infections – athlete’s foot.
   • Used for stomach wash in alkaloid poisoning.
   • Can also be used for the purification of well water.
   • Concentrated solution can cause burns and blisters on topical application.
   • Not used to disinfect surgical instruments, as it promotes rusting.

Halogens

They are oxidizing agents.

1. Chlorine: It is used for disinfection of water. Some of its preparations are:
   • Chloramines: They act by releasing chlorine. They can be used as mouthwash and for dressing of wounds.
   • Chlorinated lime (bleaching powder)
     • Acts by releasing chlorine.
     • Used to disinfect drinking water and toilets.
     • The disadvantage is that it is highly unstable and loses its activity on storage.
2. Sodium hypochlorite
   • Used as a root canal disinfectant.
   • It is cheap but it needs to be freshly prepared and has a corrosive effect on metals.
3. Iodine
   • It has the property of oxidizing the protoplasm of microbes.
   • Hypersensitivity reactions can occur with iodine.
   • Its preparations are:
     • Tincture iodine (2% iodine in alcohol)
       1. Used as an antiseptic on skin for wounds and prior to surgery.
       2. It stains the skin.
     • Mandl’s paint
       1. It contains iodine in potassium iodide and glycerine.
       2. Used topically in tonsillitis and pharyngitis.
     • Lugol’s iodine
       1. Contains 5% iodine in a 10% solution of potassium iodide.
       2. Used in thyrotoxicosis.
     • Iodophores
       1. Act by releasing iodine, e.g. povidone iodine.
       2. Nonirritant and does not stain the skin.
       3. Used in burns, boils, prior to surgery, disinfection of instruments and endoscopes.
       4. 1% solution is used as a mouth rinse for gingivitis and before dental procedures.

Acids

Antiseptic activity is mainly due to their antibacterial activity.

1. Boric acid and sodium borate (Borax)
   • Fungistatic and bacteriostatic.
   • 2%–4% solution is used as mouthwash.
   • 30% paint for stomatitis and glossitis.
   • It is a component of prickly heat powder.
   • Systemic absorption can cause abdominal pain, diarrhea, vomiting, and kidney damage.

Metallic salts

1. Zinc sulfate
   • It has antiseptic and astringent properties.
   • Used topically for conjunctivitis, ulcers, and acne.
   • It decreases sweating, hence used as a component in deodorants.
   • Zinc salts are one of the components in calamine lotion which is used in urticaria and eczema as an antiseptic and antipruritic agent.
2. Silver nitrate
   • It is an astringent and antiseptic.
   • It can also be used as an antiseptic for oral ulcers.

Dyes

They are used topically as antiseptic. They stain the skin on application.

• Gentian violet and brilliant green are useful in gingivitis, oral thrush, bed sores, chronic ulcers, burns, etc.

Cationic Surfactants

They are benzalkonium chloride, cetrimide, and cetylpyridinium chloride.

1. Most commonly used antiseptics.
2. Benzalkonium chloride is used as an antiseptic on the skin prior to surgery and to store sterilized instruments.
3. Cetrimide (Cetavlon) is used as a preservative for eye drops and disinfecting instruments.
4. Savlon (cetrimide + chlorhexidine) is used to disinfect thermometers.

Vitamins.

They are organic substances that are required in small quantities to meet the metabolic demands of the body. Most of them are supplied through diet. They are converted in the body to coenzymes, which participate in metabolic reactions. Usually, a well-balanced diet provides the required amount of vitamins to the body.

Vitamins A, D, E, and K are fat-soluble vitamins. Water-soluble vitamins include vitamin B complex and vitamin C.

• Fat-Soluble Vitamins
• Water-Soluble Vitamins
  
  

Drug Treatment Of Medical Emergencies

Drug treatment of medical emergencies is listed in Table.

• Drug Treatment of Medical Emergencies

Dental Tray (Emergency Drug Kit) For Dentists.