Excipients
Preparations require excipients to impart a variety of properties to the compounded dosage form. From the compounder’s viewpoint, it is
prudent to understand the role of each ingredient in the completed preparation. Many times this insight may alert the compounder to
potential instabilities that might occur, clues about the preparation’s performance that would be useful/necessary to share with the patient,
or provide alternatives if the preparation is not suitable for a patient due to allergies, preferences, etc. Also, excipients have different roles
in different preparations, or oftentimes an excipient will play more than one role in a preparation.
The list below is a compilation from several reference sources. It is not an all-inclusive list, nor does it provide an absolute
classification scheme for all the excipients used in compounded preparations. It does serve as a basic template that can be expanded as
desired.
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| Ingredient | Type Definition | Examples |
|---|---|---|
| Acidifying agent | Provides acidic medium for product stability in liquid preparations. | Citric acidAcetic acidFumaric acidHydrochloric acidNitric acid |
| Alkalinizing agent | Provides alkaline medium for product stability in liquid preparations. | Ammonia solutionAmmonium carbonateDiethanolamineMonoethanolaminePotassium hydroxideSodium bicarbonateSodium borateSodium carbonateSodium hydroxideTrolamine |
| Adsorbent | Holds other molecules onto its surface by physical or chemical (chemisorption) means. | Powdered celluloseActivated charcoal |
| Aerosol propellant | Develops pressure within an aerosol container, which expels the ingredients when the valve is open. | Carbon dioxideDichlorodifluoromethaneDichlorotetrafluoroethaneTrichloromonofluoromethane |
| Air displacement | Displaces air in a hermetically sealed container to enhance product stability. | NitrogenCarbon dioxide |
| Antifoaming agent | Breaks up and inhibits the formation of foams | Dimethicone Lauric acid NF32 Myristic acid Palmitic acid Simethicone |
| Antifungal preservative | Prevents growth of fungi in liquid and semisolid preparations. Use in combination usually enhances the effectiveness of parabens. | Butylparaben Ethylparaben Methylparaben Benzoic acid Propylparaben Sodium benzoate Sodium propionate |
| Antimicrobial preservative | Prevents growth of microorganisms in liquid and semisolid preparations. | Benzalkonium chloride Methylparaben Propylparaben Sorbic acid |
| Antioxidant | Prevents deterioration of preparations by oxidation. | Ascorbic acid Ascorbyl palmitate Butylated hydroxyanisole Butylated hydroxytoluene Hypophosphorous acid Monothioglycerol Propyl gallate Sodium ascorbate Sodium bisulfite Sodium formaldehyde sulfoxylate Sodium metabisulfite |
| Buffering agent | Resists change in pH upon dilution or addition of acid or alkali. | Potassium metaphosphate Potassium phosphate, monobasic Sodium acetate Sodium citrate, anhydrous and dihydrate |
| Chelating agent | Substance that forms stable water-soluble complexes (chelates) with metals; used in some liquid pharmaceuticals as stabilizers to complex heavy metals that might promote instability. In such use, they are also called sequestering agents. | Edetic acid Edetate disodium |
| Clarifying agent | Filtering aid used for its adsorbent qualities | Bentonite Talc |
| Colorant | Imparts color to liquid and solid (e.g., tablets and capsules) preparations | FD&C Red No. 3 FD&C Red No. 20 FD&C Yellow No. 6 FD&C Blue No. 2 D&C Green No. 5 D&C Orange No. 5 D&C Red No. 8 Caramel Ferric oxide, red |
| Emolient | Softens the skin or soothes irritated skin or mucous membranes | Acetylated lanolin alcohol Cetyl acetate Cetyl lactate Cetyl ricinoleate Disopropyl adipate Disopropyl dimerate Glyceryl oleate Hexylene glycol Isopropyl isostearate Isopropyl palmitate Isostearic acid derivatives Maleated soybean oil mixtures Myristyl myristate Octyl dodecanol Octyl hydroxystearate Octyl palmitate Phenyl trimethicone Propylene glycol Tocopheryl acetate Tocopheryl linoleate Triisocetyl citrate Wheat germ glycerides |
| Emulsifying agent | Promotes and maintains dispersion of the finely subdivided particles of liquid in vehicles where it is immiscible. Liquid emulsion or semisolid emulsion may be the end product. | Acacia Agar Behenoyl Polyoxylglycerides Benzalkonium chloride Benzyl benzoate Caprylic acid Caprylocaproly – Polyoxylglycerides Carbomer Copolymer Carbomer Homopolymer Cetomacrogol Cetyl alcohol Glyceryl monostearate Sorbitan monooleate Polyoxyethylene 50 stearate (myrj23) |
| Encapsulating agent | Forms thin shells in which drug is enclosed to ease administration. | Gelatin |
| Enteric coating | Polymer barrier on tablets meant to prevent medication from breaking down in the stomach, instead allowing breakdown in the small intestine. | Cellulose acetate phthalate Shellac (35% in alcohol, pharmaceutical glaze) |
| Film coating | Polymer coating applied to tablets meant to protect the dosage form or modify its release. | Hydroxyethyl cellulose Hydroxypropyl cellulose Hydroxypropyl methylcellulose (Hypromellose) Methylcellulose (e.g., Methocel) Ethylcellulose (e.g., Ethocel) |
| Flavorant | Gives a pleasant flavor and often odor to a preparation. Synthetic flavorants may also be used in addition to the natural flavorants listed. | Anise oil Cinnamon oil Cocoa Menthol Orange oil Peppermint oil Vanillin |
| Flavoring/sweetening agent | Imparts a pleasant flavor and sweetness to a preparation. | Acacia syrup Aromatic syrup Aromatic elixir Cherry syrup Cocoa syrup Orange syrup Syrup |
| Foam adjuvant | Improves the stability and reduces the specific gravity of foam. It may increase the foaming capacity of surfactants. | Arachidic acid Arachidyl alcohol Behenic acid Behenyl alcohol Cetyl alcohol Hexadecanoic acid Octacosanoic acid Oleyl alcohol Stearic acid Stearyl alcohol |
| Foaming agent | Amphiphilic susbtance that facilitates the formation of foam. | Brij 38 Brij 52 Brij 56 Isoceteth-20 Laureth-4 Lecithin Myrj 45 Myrj 49 Myrj 59 Polyglyceryl-4 isostearate Polyoxyethylene (20) sorbitan monostearate (Tween 60) Polyoxyethylene (2) sorbitan monooleate (Tween 80) Sodium lauryl sulfate Sorbitan laurate Sorbitan monolaurate Sorbitan palmitate Triethanolamine lauryl sulfate |
| Gelling agent | Increase the viscosity of a substance; can act as a stabilizer. | Acrylic acid/ethyl acrylate copolymers Carboxymethyl cellulose Carboxyvinyl polymers Carrageenan gum Egg albumin Gelatin agar Guar gum Hydroxyethyl cellulose Hydroxypropyl guar gum Hydroxyl propylmethyl cellulose Polymethacrylic acid polymers Polyvinyl alcohol Polyvinylpyrrolidone Locust bean gum Quince seed extract Sodium alginate Sodium caseinate Starch Tragacanth gum Xanthan gum |
| Humectant | Prevents drying of preparations, particularly ointments and creams. | Glycerin Propylene glycol Sorbitol |
| Hydrophilic solvent | Liquid with high miscibility with water, used to dissolve solutes. | Azone Caprylic acid Diethylene glycol Dimethylacetamide Dimethylformamide Dimethylsulfoxide Dioxolane Di-terpenes Ethylene glycol Glycerin Hexylene glycol Lauric acid Lauryl alcohol Lemonene l-menthol Myristyl alcohol Polyethylene glycols Propylene glycol Terpeneol Terpenes |
| Hydrophobic solvent | Liquid with low or no miscibility with water, used to dissolve solutes. | Borage seed oil Canola oil Coconut oil Cod-liver oil Corn oil Cottonseed oil Docosahexaenoic acid Eicosapentaenoic acid Evening primrose oils Flaxseed oil Gamma-linoleic acid Linoleic acid Linolenic acid Mineral oil Olive oil Omega-3 and omega-6 fatty acids Salmon oil Sesame oil Some essential oils Soybean oil Sunflower oil Triglyceride oil Wheat germ oil |
| Levigating agent | Liquid used as an intervening agent to reduce the particle size of a powder by grinding, usually in a mortar. | Mineral oil Glycerin Propylene glycol |
| Ointment base | Semisolid vehicle for mediated ointments. | Lanolin Hydrophilic ointment Polyethylene glycol ointment Petrolatum Hydrophilic petrolatum White ointment Yellow ointment Rose water ointment |
| pH Modifier (Acidifying agent/Alkalizing agent/Buffering agent) |
Decreases or increases pH in preparations or protects compounds from rapid change in pH. | Acetic acid Acetic acid, glacial Adipic acid Ammonia solution, strong Ammonium carbonate Ammonium chloride Ammonium phosphate Boric acid Calcium carbonate Calcium hydroxide Calcium lactate Calcium phosphate, tribasic Citric acid, monohydrate Citric acid, anhydrous Diethanolamine Fumaric acid Glycine Hydrochloric acid Hydrochloric acid, diluted Alpha-lactalbumin Lactic acid Lysine hydrochloride Maleic acid Methionine Monoethanolamine Monosodium glutamate Nitric acid Phosphoric acid Phosphoric acid, diluted Potassium bicarbonate Potassium citrate Potassium hydroxide Potassium metaphosphate Potassium phosphate, dibasic Potassium phosphate, monobasic Propionic acid Racemethionine Sodium acetate Sodium bicarbonate Sodium borate Sodium carbonate Sodium citrate Sodium hydroxide Sodium lactate solution Sodium phosphate, dibasic Sodium phosphate, monobasic Succinic acid Sulfuric acid Tartaric acid Trolamine |
| Plasticizer | Component of film-coating solutions to make film more pliable, enhance spread of coat over tablets, beads, and granules. | Diethyl phthalate Glycerin |
| Solvent | In preparation of a solution, aqueous or oleaginous solvent may be used to dissolve another substance. Water and hydroalcoholic alcohol, water and glycerin may be used as co-solvents when needed. Sterile solvents are used in preparations such as injections. | Alcohol Bacteriostatic Sodium Chloride Injection Corn oil Cottonseed oil Glycerin Isopropyl alcohol Mineral oil Oleic acid Peanut oil Purified water Water for Injection Sterile Water for Injection Sterile Water for Irrigation |
| Stiffening agent | Increases thickness or hardness of a preparation, usually an ointment | Cetyl alcohol Cetyl esters wax Microcrystalline wax Paraffin Stearyl alcohol White wax Yellow wax |
| Sugar coating | Sweetened outer layer on oral solid dosage forms. | Liquid glucose Sucrose |
| Suppository base | Vehicle for suppositories | Cocoa butter Polyethylene glycols (mixtures) PEG 3350 |
| Surfactant (surface-active agent) | Substances that absorb to surfaces or interfaces to reduce surface or interfacial tension. May be used as wetting agents, detergents, or emulsifying agents. | Benzalkonium chloride Nonoxynol 10 Octoxynol 9 Polysorbate 80 Sodium lauryl sulfate Sorbitan monopalmitate |
| Suspending agent | Viscosity-increasing agent used to reduce sedimentation rate of particles in a vehicle in which they are not soluble; suspension may be formulated for oral, parenteral, ophthalmic, topical, or other route. | Agar Bentonite Carbomer (e.g., Carbopol) Carboxymethylcellulose sodium Hydroxyethyl cellulose Hydroxypropyl cellulose Hydroxypropyl methylcellulose Kaolin Methylcellulose Tragacanth Veegum |
| Sweetenign agent | Gives sweetness to a preparation | Aspartame Dextrose Glycerin Mannitol Saccharin sodium Sorbitol Sucrose |
| Tablet anti-adherent | Prevents tablet ingredients from sticking to punches and dies during production | Magnesium stearate |
| Tablet binder | Substances that cause adhesion of powder particles in tablet granulations | Acacia Alginic acid Carboxymethylcellulose sodium Compressible sugar (e.g., Nu-Tab) Ethylcellulose Gelatin Liquid glucose Methylcellulose Povidone Pregelatinized starch |
| Tablet and capsule diluent | Inert filler that creates desired bulk, flow properties, and compression characteristics of tablets and capsules. | Dibasic calcium phosphate Kaolin Lactose Mannitol Microcrystalline cellulose Powdered cellulose Precipitated calcium carbonate Sorbitol Starch |
| Tablet direct compression excipient | For use in direct compression tablet formulations. | Dibasic calcium phosphate (e.g., Ditab) |
| Tablet disintegrant | Promotes disruption of the mass in a solid form into smaller particles that are more easily dispersed or dissolved. | Alginic acid Polacrilin potassium (e.g., Amberlite) Sodium alginate Sodium starch glycolate Starch |
| Tablet glidant | Improves flow of properties of the powder mixture in tablet and capsule formulations | Colloidal silica Cornstarch Talc |
| Tablet lubricant | Reduces friction of tablet formulations during tablet compression | Calcium stearate Magnesium stearate Mineral oil Stearic acid Zinc stearate |
| Tablet or capsule opaquant | Renders a coating opaque when used alone or with a colorant. | Titanium dioxide |
| Tonicity agent | Makes a solution similar in osmotic dextrose characteristics to physiologic fluids, such as irrigation, ophthalmic, and parenteral fluids. | Sodium chloride |
| Vehicle | A base used in a variety of liquids for oral and parenteral administration. Oral liquids are aqueous (e.g., syrups) or hydroalcoholic (e.g., elixirs). Solutions for intravenous use are aqueous, whereas intramuscular injections may be aqueous or oleaginous. | |
| Viscosity-increasing agent | Renders preparations more resistant to flow. In suspensions sedimentation is deterred, contact time is enhanced in ophthalmic solutions (e.g., methylcellulose), and topical creams are thickened. | Alginic acid Bentonite Carbomer Carboxymethylcellulose Sodium Methylcellulose Povidone Sodium alginate Tragacanth |
| Water-miscible co-solvent | Increases the solubility of poorly water soluble substances or enhances the chemical stability of a drug. | Ethanol Glycerin Isopropanol Polyethylene glycol Propylene glycol |
| Water-repelling agent | Hydrophobic material used as a non-sticky lubricant in lotions, in creams, or as an enhancer and stabilizer in foams. | Cyclomethicone Dimethicone Simethicone |
| Wetting and/or solubilizing agent | Reduces the surface tension of water, allowing it to spread more easily, and/or improves the solubility of poorly water soluble drugs. | Betadex Sulfobutyl Ether Sodium |
Adapted from:
“Dosage Form Designs: Pharmaceutical and Formulation Considerations,” by L. V. Allen, Jr. and H. C. Ansel, chap. 4 in Ansel’s Pharmaceutical Dosage Forms and Drug Delivery Systems, 10th ed. (Baltimore: Lippincott Williams & Wilkins, 2012): 102–165.
Excipients: USP and NF Excipients, Listed by Functional Category: USP−NF Online. (Rockville, MD: United States Pharmacopeial Convention, 2014).
“Preservatives, Antioxidants, and pH,” by L. V. Allen, Jr., Secundum Artem 18, no. 1: 1–8. Available online. URL: http://www.perrigo.com/business/education.aspx.
“Foam Dosage Forms,” by L.V. Allen, Jr. International Journal of Pharmaceutical Compounding 17, no. 4 (2013): 312–322.
USP–NF Chapter <1059> Excipient Performance: USP−NF Online. (Rockville, MD: United States Pharmacopeial Convention, 2014).