PHARMACEUTICAL EXCIPIENTSPHARMACEUTICAL EXCIPIENTS

An Excipient is usually an inert substance added to the drug to give suitable consistency or definite form to the drug. It is also called pharmaceutical necessity or aid.

PHARMACEUTICAL EXCIPIENTSPHARMACEUTICAL EXCIPIENTS

There are various types of pharmaceutical excipients used in the compounding of the pharmaceutical dosage forms. We will discuss about chemistry, Physical properties and uses of them.

Lists of the important excipients:1. Antioxidants 2. Preservatives3. Humectants4. Ointment bases

PHARMACEUTICAL EXCIPIENTSPHARMACEUTICAL EXCIPIENTS

5. Acidifying agents6. Air displacement agents7. Alkalizing agents8. Antifoaming agents 9. Buffering agents10. Chelating agents

PHARMACEUTICAL EXCIPIENTSPHARMACEUTICAL EXCIPIENTS

11. Coloring agents12. Flavouring agents and Perfumes13. Stiffening agents13. Wetting and Solubilizing agents15. Complexing agents, Emulsifying agents16. Solvents.

Antioxidants

An antioxidant is a substance capable of inhibiting oxidation and that may be added for this purpose to pharmceutical products subject to detereoration by oxidative processes as, for example , the development of rancidity in oils and fats or the inactivation of some medicinals in the environment of their dosage form.E.g. BHA (Butylated Hydroxyanisole)BHT (Butylated Hydroxytoluene)Ascorbic acid, Alpha Tocopherol (Vit-E) e.t.c

Antioxidants

Mechanism of action: Most antioxidant function by providing electron or labile H+ which will be accepted by any free radical to terminate the chain reaction.

The selection of Antioxidants

The following criteria’s should be brought into consideration while selecting a suitable antioxidant for pharmaceutical purposes:

o It should be capable of ensuring desired redox reaction when used in pharmaceutical preparations.

o It should be chemically compatible i.e. it should not react with other chemicals in the preparations.

The selection of Antioxidants

o It should not alter the solubility of other components.

o It should also exhibit reasonable chemical stability.

o It should be effective at a very low concentration.

o It should be physiologically inert.

o It should be safe and nontoxic.

Ascorbic Acid

Chemistry: Ascorbic acid is an organic acid. It is also called Vitamin C. Chemical formula: C6H8O6

Structure:

Ascorbic Acid

Physical Properties:Description: It’s appearance is white to slightly yellow crystals or powder.Solubility: Water soluble.

Use: It is used as an antioxidant to retard oxidative degradation of various pharmaceuticals.

BHA (Butylated Hydroxyanisole)BHA (Butylated Hydroxyanisole)

Chemistry :1,1-dimethylethyl-4-methoxy phenol

Physical Properties:Description: White or slightly yellow, waxy solid having a faint, characteristic odor.

BHA (Butylated Hydroxyanisole)BHA (Butylated Hydroxyanisole)

Solubility: Insoluble in water, soluble in alcohol, chloroform or ether.

Uses: it is used as an antioxidant in pharmaceutical products containing fats and oils.

BHT ( Butylated Hydroxytoluene )

Chemistry: 1,1-dimethylethyl-4-methyl phenol.

Physical properties:Description: White, tasteless crystals with a mild odor, stable in light or air, melting point 700C.Solubility: Insoluble in water, soluble in alcohol, chloroform and water.

Uses: It is used as an antioxidant to retard oxidative degradation of oils & fats in various pharmaceuticals.

Preservatives

A preservative is a substance that prevents or inhibits the growth of microorganisms and is added to pharmaceutical preparation to avoid consequent spoilage of the preparation by microorganism.e.g. Methyl parabenEthyl ParabenPropyl parabenBenzoic acid

Preservatives

e.g. Sodium benzoate

Benzalkonium chloride Benzyl alcohol Chlorobutanol Phenol Thiomerosal

Preservatives Desirable features of a preservative suitable

for use in pharmaceutical formulation:1. A wide spectrum of activity against all

bacteria, yeasts and moulds.2. Bactericidal rather than Bacteriostatic .3. Freedom from toxic, irritant or sensitizing

activity.4. Compatibility with other ingredients and

with the container.5. High water solubility.6. Stability and effectiveness over a wide

range of pH and Temp.7. Freedom from color and odor.

Potassium Benzoate

Chemistry: Potassium salt of benzoic acid.Structure:

COOK . 3H2O

Potassium Benzoate

Physical Properties:Description: Crystalline powderSolubility: Soluble in water

Use: It is used as an antimicrobial preservative in pharmaceutical preparation.

Phenol

Chemistry: It is also called carbolic acid.Structure:

OH

Physical Properties:Description: Colorless to light pink, needle shaped crystals, characteristic odor.

Phenol

Solubility: 1g in 15 ml water, very soluble in alcohol, glycerin, chloroform & ether.

Use: It is used as a preservative for injectable preparations at 0.5% w/v.

Chlorobutanol

Chemistry: 1,1,1-trichloro-2-methyl-2-propanolStructure: (CCl3)C(CH3)2OH

Physical Properties:Description: Colorless to white crystals, camphoraceous odor and taste, anhydrous melts at 950C ; hydrous melts at 760C.

Chlorobutanol

Solubility: 1g in 125 ml water; 1 ml alcohol or 10 ml glycerin; freely soluble in chloroform, ether or volatile oils.

Use: It is primarily used as preservative in ophthalmic and parenteral preparations as it has antimicrobial & germicidal properties.

Methyl Paraben

Chemistry: It is the methyl ester of parahydroxybenzoic acid.Structure:

CH3

Physical properties

Description: Colorless crystals or white powder. Solubility: soluble in water, ethanol, slightly soluble in benzene and acetone.

Uses: It is used as preservative in pharmaceutical formulation to inhibit the growth of microorganisms.

Acidifying agentsAcidifying agents

Substances that are used in liquid preparation to provide acidic media for product stability.e.g. Citric acidAcetic acidFumaric acidHydrochloric acidNitric acid

Citric AcidCitric Acid

Chemistry: 2-hydroxy-1,2,3-propane tricarboxylic acid.

Structure:

HOCCOOH

CH2COOH

CH2COOH

Physical Properties:Description:Colorless, Translucent crystals or a white granular to fine crystalline powder. Strongly acid taste & odorless.Solubility: Very soluble in water, freely soluble in methanol, soluble in ether.

Use: It is used as an acidifying agent to stable the product providing appropriate pH.

Citric AcidCitric Acid

Acetic acid

Chemistry: It is also called ethanoic acid or methane carboxylic acid.Structure:

Acetic acid

Physical properties:Description: Colorless liquidor crystals. Molecular mass-60 g/molSolubility: Completely miscible with water, ethanol, acetone.

Use: It is used as an acidifying agent to stable the product providing appropriate pH.

Alkalizing Agent

Alkalizing Agent are substances that are used in liquid preparation to provide alkaline media for product stability.

e.g. Ammonia solutionAmmonia carbonateDiethanolaminePotassium HydroxideSodium BorateSodium carbonateTrolamine

Sodium Borate

Chemical Formula: Na2B4O7.10H20 Physical Properties:

Description: colorless, transparent crystals or a white crystalline powder, odorless. pH-9.5Solubility: soluble in water & glycerin but insoluble in alcohol.

Use: It is used as an Alkalizing Agent in liquid preparation to provide appropriate pH for product stability.

Sodium Carbonate

Chemistry: Sodium carbonate (also known as washing soda or soda ash), Na2CO3, is a sodium salt of carbonic acid. It is decomposed by weak acids forming salts of the acid and liberate CO2

Chemical formula: Anhydrous Na2CO3

Na2CO3.2H2O

Sodium Carbonate

Physical Properties:Description: Colorless crystals or a white crystalline powder. Aqueous solution is alkaline to litmus, pH-11.5. Solubility: Soluble in water but insoluble in alcohol.

Use: It is used as an Alkalizing Agent in liquid preparation to provide appropriate pH for product stability.

Sodium Bicarbonate

Chemistry: Sodium bicarbonate NaHCO3, or sodium hydrogen carbonate, also known as baking soda, bread soda, or bicarbonate of soda.Chemical structure:

Sodium Bicarbonate

Physical properties:

Description: soluble white anhydrous or crystalline chemical compound, with a slight alkaline taste resembling that of sodium carbonate. Solubility: 1g in 10ml water.

Use: It is used as an Alkalizing Agent in liquid preparation to provide appropriate pH for product stability.