Skip to main content

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
Back to Top of Table

IngredientType DefinitionExamples
Acidifying agentProvides acidic medium for product stability in liquid preparations.Citric acidAcetic acidFumaric acidHydrochloric acidNitric acid
Alkalinizing agentProvides alkaline medium for product stability in liquid preparations.Ammonia solutionAmmonium carbonateDiethanolamineMonoethanolaminePotassium hydroxideSodium bicarbonateSodium borateSodium carbonateSodium hydroxideTrolamine
AdsorbentHolds other molecules onto its surface by physical or chemical (chemisorption) means.Powdered celluloseActivated charcoal
Aerosol propellantDevelops pressure within an aerosol container, which expels the ingredients when the valve is open.Carbon dioxideDichlorodifluoromethaneDichlorotetrafluoroethaneTrichloromonofluoromethane
Air displacementDisplaces 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
Antifungal preservative Prevents growth of fungi in liquid and semisolid preparations. Use in combination usually enhances the effectiveness of parabens. Butylparaben
Benzoic acid
Sodium benzoate
Sodium propionate
Antimicrobial preservative Prevents growth of microorganisms in liquid and semisolid preparations. Benzalkonium chloride
Sorbic acid
Antioxidant Prevents deterioration of preparations by oxidation. Ascorbic acid
Ascorbyl palmitate
Butylated hydroxyanisole
Butylated hydroxytoluene
Hypophosphorous acid
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
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
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
Behenoyl Polyoxylglycerides
Benzalkonium chloride
Benzyl benzoate
Caprylic acid
Caprylocaproly – Polyoxylglycerides
Carbomer Copolymer
Carbomer Homopolymer
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
Orange oil
Peppermint oil
Flavoring/sweetening agent Imparts a pleasant flavor and sweetness to a preparation. Acacia syrup
Aromatic syrup
Aromatic elixir
Cherry syrup
Cocoa syrup
Orange 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
Myrj 45
Myrj 49
Myrj 59
Polyglyceryl-4 isostearate
Polyoxyethylene (20) sorbitan monostearate
(Tween 60)
Polyoxyethylene (2) sorbitan monooleate (Tween
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
Locust bean gum
Quince seed extract
Sodium alginate
Sodium caseinate
Tragacanth gum
Xanthan gum
Humectant Prevents drying of preparations, particularly ointments and creams. Glycerin
Propylene glycol
Hydrophilic solvent Liquid with high miscibility with water, used to dissolve solutes. Azone
Caprylic acid
Diethylene glycol
Ethylene glycol
Hexylene glycol
Lauric acid
Lauryl alcohol
Myristyl alcohol
Polyethylene glycols
Propylene glycol
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
Propylene glycol
Ointment base Semisolid vehicle for mediated ointments. Lanolin
Hydrophilic ointment
Polyethylene glycol ointment
Hydrophilic petrolatum
White ointment
Yellow ointment
Rose water ointment
pH Modifier (Acidifying
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
Fumaric acid
Hydrochloric acid
Hydrochloric acid, diluted
Lactic acid
Lysine hydrochloride
Maleic acid
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
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
Plasticizer Component of film-coating solutions to make film more pliable, enhance spread of coat over tablets, beads, and granules. Diethyl phthalate
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
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
Stearyl alcohol
White wax
Yellow wax
Sugar coating Sweetened outer layer on oral solid dosage forms. Liquid glucose
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
Carbomer (e.g., Carbopol)
Carboxymethylcellulose sodium
Hydroxyethyl cellulose
Hydroxypropyl cellulose
Hydroxypropyl methylcellulose
Sweetenign agent Gives sweetness to a preparation Aspartame
Saccharin sodium
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)
Liquid glucose
Pregelatinized starch
Tablet and capsule diluent Inert filler that creates desired bulk, flow properties, and compression characteristics of tablets and capsules. Dibasic calcium phosphate
Microcrystalline cellulose
Powdered cellulose
Precipitated calcium carbonate
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
Tablet glidant Improves flow of properties of the powder mixture in tablet and capsule formulations Colloidal silica
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
Sodium alginate
Water-miscible co-solvent Increases the solubility of poorly water soluble substances or enhances the chemical stability of a drug. Ethanol
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
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:

“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).