Locally Acting Drugs (Dental Pharmacology) PDF

Locally acting drugs (dental pharmacology) Prof Dr Barakat  WHAT ARE LOCALLY ACTING DRUGS? agents applied topically to the skin or mucous membranes to produce therapeutic effects localized to the site of application. Prof Dr Mervat Barakat  Some of locally acti...

Locally acting drugs (dental pharmacology) Prof Dr Barakat  WHAT ARE LOCALLY ACTING DRUGS? agents applied topically to the skin or mucous membranes to produce therapeutic effects localized to the site of application. Prof Dr Mervat Barakat  Some of locally acting drugs relevant to dentistry are: 1. Antiseptics. 2. Demulcents. 3. Adsorbants and protectives 4. Astringents and obtundents 5. Vasoconstrictors 6. Hemostatic Agents. 7. Antiplaque agents. 8. Styptics (local haemostatics) 9. Obtundant 10. Dental caries and fluorides Prof Dr Mervat Barakat  Substantivity It is the period that a drug is in contact with a particular substrate in the oral cavity. Substantivity refers to the persistence of the substance on the surface of teeth/gums due to initial binding and subsequent slow release Prof Dr Mervat Barakat Substantivity depends on two important features: The degree of reversible nonspecific binding to oral reservoirs (these include the enamel, dentin, the oral mucosa, salivary proteins, and the organic and inorganic components of plaque). The rate of clearance by salivary flow. The clearance of an agent from the oral cavity is directly proportional to the rate of salivary flow. Prof Dr Mervat Barakat 1. Antiseptics applied on the body surfaces to prevent/cure infection by killing or inhibiting the growth of pathogenic bacteria.Spectrum of activity of majority of antiseptic disinfectants is wide. Prof Dr Mervat Barakat Classification of antiseptics: 1. Phenol derivatives: Phenol 2. Oxidizing agents: Hydrogen peroxide. 3. Halogens: Iodine. 4. Biguanide: Chlorhexidine. 5. Soaps: of sodium and potassium. 7. Alcohols: Ethanol, Isopropanol. 8. Aldehydes: Formaldehyde. 9. Acids: Boric acid, Acetic acid. 10. Metallic salts: Silver nitrate. 11. Dyes: Gentian violet. Prof Dr Mervat Barakat Mechanisms of action of antiseptics can be grouped into: 1. Oxidation of bacterial protoplasm. 2. Denaturation of bacterial proteins including enzymes. 3. Increasing permeability of bacterial membrane Prof Dr Mervat Barakat Factors which modify the activity of antiseptics are: 1. Temperature and pH. 2. Period of contact with the microorganism. 3. Nature of organisms involved. 4. Size of innoculum. 5. Presence of blood, pus or other organic matter. Prof Dr Mervat Barakat  Indications of antiseptic mouth wash: 1. Reduces oral infections in immunocompromised patients (cancer, AIDS) 2. Healing phase after oral and periodontal surgery. 3. Treatment of infective oral conditions (Acute necrotizing ulcerative gingivitis, aphthous ulcers). 4. Treatment of denture associated stomatitis. 5. Routine mouth wash to prevent plaque formation and gingivitis. Prof Dr Mervat Barakat Chlorhexidine Prof Dr Mervat Barakat Chlorhexidine is a powerful, nonirritating Disrupts bacterial cell membrane. The most widely used antiseptic in dentistry, mainly in the form of oral rinse (0.12–0.2%) or toothpaste (0.5–1%). Much of the chlorhexidine binding in the mouth occurs on the mucous membranes, such as the alveolar and gingival mucosa, from which sites it is slowly released in active form. Prof Dr Mervat Barakat Side effects of chlorhexidine 1. Brownish discoloration of teeth and tongue. 2. Unpleasant after-taste. 3. Impaired taste sensation, for salt but not for sweet, bitter, and sour. 4. Occasionally oral ulceration (with use of drug concentrations exceeding 0.2% or after prolonged application). Prof Dr Mervat Barakat 2. Demulcents  They are inert substances which sooth inflamed/denuded mucosa  They are, in general, high molecular weight substances and are applied as thick colloidal/viscid solutions in water.  Examples: Glycyrrhiza (liquorice): used to sooth the throat and as flavouring/ sweetening agent. Glycerine, It also has mild antiseptic property. Methylcellulose Prof Dr Mervat Barakat 3. Adsorbants and protectives  powdered, inert and insoluble solids capable of binding to noxious and irritant substances afford physical protection to the skin or mucosa. Sucralfate (an aluminium salt of sulfated sucrose) is formulated as a topical gel to be applied on aphthus ulcers. It serves to facilitate healing by covering the denuded surface. Prof Dr Mervat Barakat 4. Astringents They are substances that precipitate proteins. Examples include: Tannic acid. Heavy metal salts (zinc chloride, zinc sulfate, aluminium chloride, ferrous sulfate) Indications of astringents: 1. Symptomatic relief of pain. 2. Promote healing of oral lesions. 3. Reduce dentine sensitivity. 4. Reduce gum bleeding. Prof Dr Mervat Barakat 5. Vasoconstrictors  In dentistry either as components of the local anesthetic syringe or for application with gingival retraction cords. These agents act by constricting blood vessels; Examples of vasoconstrictors include: Epinephrine (1:200,000/1:100,000/1:50,000), and Norepinephrine (1:30,000). Epinephrine is the vasoconstrictor of choice for use in dentistry.  Vasoconstrictors should be avoided 1. Uncontrolled hypertension. 2. Uncontrolled hyperthyroidism. 3. Patients with angina,Profor recent myocardial infarction. Dr Mervat Barakat 6. Hemostatic Agents Hemostatic agents are used in dentistry for hemorrhage control. Examples of hemostatic include: 1. Thrombin: It acts by accelerating the coagulation of blood. It should be applied locally and never injected. 2. Gelatin sponge (Gel Foam): It is available as a powder or porous sheet. Prof Dr Mervat Barakat 7. Antiplaque Agents:  Effective therapy of plaque requires that the drug applied as mouth rinse, gels or tooth paste remains at the site without being washed away to exert sustained antimicrobial effect.  Most important properties of an antiplaque agent are 1. Antimicrobial spectrum covering the relevant microbes 2. ‘substantivity’ which refers to persistence of the substance on the surface of teeth/gums due to initial binding and subsequent slow release. Prof Dr Mervat Barakat  Antiplaque agents 1. Chlorhexidine 2. antiseptics: Benzalkonium chloride 3. Phenols 4. Oxygenating agents: Hydrogen peroxide, 5. Zinc citrate 6. Stannous fluoride Prof Dr Mervat Barakat  Fluorides It is effective in preventing carious lesions, relatively poor antibacterial properties Fluorides are used for their caries inhibiting effect but not for plaque inhibition. Prophylactically, sodium fluoride can be used in drinking water and one part of fluoride to one million part of drinking water is sufficient for reducing the incidence of dental caries by 50%. Therapeutically, 2% sodium fluoride solution is applied locally to the teeth of fluoride after cleaning. Caution may cause nausea, vomiting and abdominal pain and on chronic ingestion it may lead to chronic fluoride poisoning and also affects enamel and dentine of developing teeth. Prof Dr Mervat Barakat 8. Obtundants  They are drugs used topically to alleviate sensitivity of the dentine to allow painless excavation.  Examples: Clove oil , Camphor , Thymol, Menthol, Alcohol.  Obtundants act by: 1. Paralysis of nerve fibers (clove oil). 2. Precipitate nerve fiber proteins (silver nitrate, alcohol)  Clove oil: has mild analgesic and antiseptic properties. Its principle constituent is euginol. It should be kept in a well-closed container protected from light.  Advantages:  It has a prolonged effect without irritation.  Disadvantages:  Yellowish coloration of dentine.  Slow penetration. Prof Dr Mervat Barakat  9. Mummifying agents  Astringents + antiseptics harden and dry tissues of the pulp and root canal so that the tissues are resistant to infection.  It is used in certain dental procedures when it is not possible to completely remove the pulp and contents of root canal.  Mummifying agents are used in the form of paste or semi-liquid preparation like tannic acid glycerine. Prof Dr Mervat Barakat  The following are mummifying agents used in dentistry. Tannic acid - It is an astringent which is yellowish white to light brown - It is used along with glycerine and it hardens the tissues and precipitates proteins and avoids bacterial action. Iodoform - It acts by slow liberation of iodine and has both antiseptic and local anodyne properties. - It is used in the form of paste which contains tannic acid, phenol, eugenol (clove oil), cinnamon oil and glycerine. Prof Dr Mervat Barakat  Paraform (paraformaldehyde): - Combination of zinc oxide or zinc sulphate glycerine and creosote and act by slow liberation of fomaldehyde. - Alone as obtundents. - Its main disadvantage is that formaldehyde may penetrate the pulp and can cause inflammation Prof Dr Mervat Barakat 10.Bleaching agents  used to remove pigmentation of teeth. They are classified as – Oxidizing agents e.g. sodium peroxide – Reducing agents e.g sodium thiosulphate – Chlorinated lime – Ultraviolet rays Oxidizing agents - Hyrdrogen peroxide in various percentages e.g. (30% H2O2 in water) and sodium peroxide (50% aqueous solution) are used as oxidizing agents to remove pigmentation of teeth. Prof Dr Mervat Barakat  Reducing agents Saturated solution of sodium thio sulphate is used to remove superficial stains with silver, iodine or permanganate. Chlorinated lime It is a chlorine compound, which acts by evolution of chlorine to remove the pigmentation of teeth. It is also used clinically by packing into the cavity as a dry powder. Ultraviolet rays To bleach the dentine from a carbon or mercury, arc lamp UV rays have been used. Prof Dr Mervat Barakat