Definition of dosage form Classification of dosage forms

Dosage form is the modified form of the drug that is suitable for administration by various routes. Dosage forms are meant for both treatment and diagnosis of the disease. The method of combining an active substance with binding, suspending, sweetening agents and preservatives to prepare a dosage form is called formulation. For example depending on the route of administration the dosage forms are categorised into tablets, capsules, syrups, injections, suppositories and transdermal patches. During the preparation of dosage forms excipients are added to reduce the unpleasant taste or to increase bulk of the active drug. Excipients on their own do not have any pharmacological action (Eg: Lactose and starch). Preparation of dosage forms meant for oral or parenteral use require liquids that are used to dissolve the drug into the formulation. These liquids are called vehicles.

Classification of Dosage forms

Classification of Dosage forms
Classification of Dosage forms

Solid Dosage Forms

1 Powder

Powder are fine, dry particles that may contain a single drug or a combination of drugs meant for Example

Analgesics: Asprin, paracetamol, caffeine.

Antacids and laxatives: Magnesium carbonate.

Dusting powders: Purified tale, kaoline.

Surgical dusting powder: Zinc undecanoate.

Nasal inhalants/snuffs: Antiseptics, bronchodilators.

Dentifrices: Calcium sulphate, sodium chloride, sodium carbonate, magnesium carbonate.

2. Effervescent Powder

These powder contain effervescent material such as sodium bicarbonate, that release CO2 when mixed with water. This makes the drug more suitable for administration.

3 Granules

Granules are formed by the agglomeration of particles of the drug substance, a mixture of drug or drugs with other binding substance


  1. Anthelmintic: Bephenium granules.
  2. Antitubercular agent: Sodium amino salicylate, isoniazid.
  3. Vitamin D, granules

4 Effervescent Granules

These are prepared by adding citric acid, tartaric acid or sodium phosphate along with sodium bicarbonate. These may be dissolved in sufficient volume of water to make solutions for oral use. Examples: Inorganic salts such as magnesium sulphate, sodium sulphate, sodium phosphate and lithium citrate.

5 Tablets Dosage Forms

They are disc like preparations formed by compression of granules, that may contain a single active ingredient or a combination of drugs, primarily meant for swallowing.

a) Uncoated Tablets

These tablets are simply compressed and are uncoated. Examples: Aspirin, paracetamol, tetracyclines, antiemetics and antibiotics.

b) Sugar Coated Tablets

Tablets after compression are coated with a water soluble sugar coating that may be coloured or not. It makes the tablet sweet and more palatable by camouflaging its bitter taste. Examples: Metronidazole, ethionamide tablets, rifampin and trimethoprim.

c) Film Coated Tablets

These tablets have a coloured, shiny appearance. Cellulose or methylcellulose dissolved in plasticizers is used for this purpose. It does not contribute weight to the tablet as in the case of sugar coating.

Example: Diltiazem

(d) Enteric Coated Tablets

When the drug substance is destroyed in the gastric acid or when it irritates the gastric mucosa or when it is meant to be released only in the intestines the tablet is enteric coated. It is a type of delayed action tablet. Shellac, gelatin and cellulose acid pthalate are used as coatings.

Examples: Esomeprazole, diclofenac sodium, pantoprazole, cetrizine

e) Retard Tablets

Inert resins are used for different coatings over the drug substances so that each layer dissolves at different stages in the gastrointestinal tract. This result in a constant and prolonged release of the drug.

Examples: Nifedipine retard tablets, potassium chloride retard tablets, acetazolamide retard tablets, prednisolone sodium phosphate retard tablets, sulfasalazine delayed release.


These are small cylindrical compressed solids formed from drug powder, implanted subcutaneously for a constant release of drug at the targeted site. The effect of which lasts for weeks or months.

Examples: Steroidal hormones, contraceptives.

g) Lozenges

These are layered, flat and harder when compared to an ordinary tablet. They are tightly compressed to reduce the rate of dissolution as they are meant to be sucked or chewed for local effects. They contain sugar, gum and medicated substance. They are also called trouches.

Examples: Benzalkonium lozenges, benzocaine lozenges.

6 Capsule

These are small shells made of soft or hard gelatin. These are filled with powders or granulated pellets or liquids that may or may not contain excipients. They are used orally. Examples:

(1) Soft gelatin capsules – Cod liver oil, vitamin A and D, multivitamins.

(ii) Hard gelatin capsules – Phenytoin sodium, chloramphenicol, lansoprazole.

7 Spansules

These are hard gelatin capsules which contains pellets made of agglomerated drug material meant for sustained release.

Examples: Isosorbide dinitrate, Iron formulations.

Liquid Dosage Forms

1 Solutions

Solutions consist of active ingredients dissolved in aqueous media or non-aqueous media or both. The dissolving medium is known as solvent and it is present in large volumes. The active ingredient is known as solute that may be a solid, liquid or gas.


(i) Solid solutes – Antibiotic, iron compounds.

(ii) Liquid solutes – Peppermint oil, cinnamon oil

(iii) Gaseous solutes – Ammonia, hydrochloric acid.

Aqueous solutions contain water as solvent and are used as douches, enemas, gargles, mou washes, syrups, etc.

Non aqueous solutions contain solvent other than water and are used as inhaler and lotion.

(a) Syrups Dosage Forms

It is a concentrated solution of sugar, sucrose or its substitutes along with a drug, flavouring agent, antimicrobial agent and preservative


  • Analgesic – Meperidine HCI syrup
  • Antihistaminic-Chlorpheniramine syrup
  • Antitussive-Diphenhydramine syrup
  • Haematinic – Ferrous sulphate syrup.

(b) Linctus

Linctus is a thick syrup that is used without dilution. It contains demulcents that provide a protective coating and reduces irritation of mucosal membrane of the throat. They are also used as antitussive or expectorant.

Examples: Codeine, ammonia, acetomorphine.

(c) Douches

It is an aqueous solution intended to be instilled into or directly inserted into a body cavity in order to clean, deodorize or soothen it.


  • Antimicrobial, antiseptics-Benzalkonium chloride, chlorhexidine
  • Antipruritic (relieves itching) – Phenol, menthol
  • Anaesthetics-Xylocaine, prilocaine Astringents – Zinc sulphate, alums.

(d) Injections

It is a sterile, pyrogen free solution or suspension of drugs. It can also be prepared b dissolving the active drug preparation in water for injection before use.


Chloramphenicol injection Procaine penicillin injection.

Depot/Repository Injection: The drug is incorporated in an oily base such as fixed oils oleic acid esters that serves as a storage reservoir and releases the drug in synthetic circula for extended periods.


  • Testosterone depot injection
  • Fluphenazine depot injection.

2. Suspensions

Suspensions are coarse dispersions. They are defined as biphasic (heterogenous systems) liquid dosage form of medicaments in which insoluble solid particles (dispersed phase) are suspended uniformly in a liquid or semisolid phase (continuous phase).

Example: Fluorometholone eye suspension, sucralfate suspension, metoclopromide HCI suspension.

a) Mixture

Solid drug particles are uniformly dissolved in a solvent, i.e., water by using suspending agents such as agar and tragacanth to increase the viscosity and reduce the sedimentation of the particles.

Example: Milk of magnesia, antidiarrhoeal mixtures, expectorants and carminatives.

b) Emulsions

Emulsions are formed by mixing two or more immiscible substances such that one is a dispersed phase and the other continuous phase. The dispersed phase (oil) is distributed uniformly in the continuous phase (water) in oil-in-water emulsion, similarly we have water in-oil emulsion Use of emulsifying agents is necessary to impart stability.

Example: Retinoic acid eye emulsion, cyclosporine eye emulsion

3 Alcoholic Solutions

In these solutions the active ingredient is dissolved in alcoholic media.

(a) Collodions

Pyroxylin (4% w/v) is dissolved in a solvent mixture of ether and alcohol (3: 1) resulting into a highly volatile and inflammable collodion. They are used for topical application.

Examples: Flexible collodion, salicylic acid collodion.

(b) Spirits

Spirit is prepared by dissolving volatile oils in alcohol or hydroalcoholic solvents. Spirits have flavoring and medical use.

Examples: Camphor spirit, peppermint spirit, aromatic ammonia spirit.

(c) Elixirs

Elixir is less viscous when compared to syrup. It is hydroalcoholic solution that may or may not contain medicaments. It may be used as a vehicle or as therapeutic substance. It also contains sweeteners i.e. saccharine, flavouring and colouring agents.

Examples: Diphenhydramine elixir, digoxin elixir

4 Drops

These are highly concentrated drug solutions meant for paediatric purpose. Specified concentrations are prepared for nasal, ocular and aural use. They should be sterile, isotonic and buffered. Examples: Pilocarpine HCI eye drops, gentamicin sulfate eye drops, benzocaine ear drops, ephedrine nasal drops.

5 Extractives

An extractive is a concentrated material obtained from plant or animal source by suitably reducing the amount of solvent so that most of the active constituent is obtained.

(a) Tinctures

Tinctures are solutions of vegetable or chemical substances that are alcoholic or hydro alcoholic depending upon the nature of the extractive. They may also incorporate glycerin, They are used orally for flavoring purpose and are also used topically.

Examples: Cardamom tincture, opium tincture, iodine tincture.

(b) Solid Extractives

They are highly concentrated preparations obtained by percolation, filtration and evaporation. These may be semiliquid’s, solids or powder extracts depending on the amount of menstrum (solvent) evaporated to achieve the desired consistency. Examples: Senna extract, belladonna extract.

6 Enema

They may be solutions, suspensions or emulsions meant to be administered in the rectum.

a) Retention Enema

These are medicated preparations for rectal administration that may produce systemic or local action.


  • Antiasthamatic – Aminophylline
  • Anthelmintic – Metronidazole
  • Anesthetic – Thiopentone sodium.
  • Anti-inflammatory – Indomethacin, prednisolone

b) Evacuation Enema

They are used for the evacuation of the bowel. They contain water in large volume, local irritants like soft soap, turpentine oil, lubricants like glycerin, mineral oil, olive oil and inorganic salts like magnesium phosphate, sodium bicarbonate, and sodium phosphate.

Dosage forms for External Use

1 Liniments

It is a solution or emulsion that has alcoholic, hydro alcoholic or oleaginous substances incorporated with the active ingredient and is meant to be used externally as rubefacient or counter-irritant. Examples: Turpentine liniment, camphor liniment.

2 Lotions

These are medicated or non-medicated suspensions or emulsions that are applied externally to provide antiseptic, astringent or soothing effect on skin. Examples: Calamine lotion for soothing effect, lindane lotion (10%) for scabies.

Eye lotions are aqueous preparations meant to be instilled into the eye cavity for cleaning it.

Example: Sodium chloride and sodium bicarbonate eye lotion.

3 Ointments

These are medicated or non-medicated semisolid preparations meant to be applied on skin, nasal mucosa or rectum. The drug in the form of solution or suspension is incorporated in an anhydrous base like lanoline, polyethylene glycol or paraffin.

Examples: Silver sulfadiazine ointment, neomycin ointment, zinc oxide ointment, soframycin ointment, atropine sulphate eye ointment.

4 Pastes

They possess a stiff consistency when compared to ointments. They are semisolids that contain one or more medicaments for local application. They contain a higher amount of fine powdered medicament which contributes stiffness to the preparation hence acts as a protective layer when applied.

Examples: Dithranol paste, zinc oxide paste, coal tar paste, zinc and coal tar paste.

5 Plasters

Plasters consist of adhesive masses such as rubber or resin with or without medicament spread on a backing like plastic, cloth etc. They exhibit prolonged contact with the skin and show protective and antiseptic action.

Examples: Salicylic acid plaster, belladonna plaster.

6 Paints

These are viscous solutions to be applied to the skin or oral mucosa. Skin paints are solutions with a collodion base to be applied on the skin. After evaporation of the solvent a resinous film of drug remains on the skin. Throat paints are viscous, non-aqueous solutions of drugs meant to be applied to the mucous membrane of throat for local action.

Examples: Compound iodine paint, compound podophyllin paint, crystal violet paint, phenol glycerin, tannic acid glycerin.

7 Gels

Gel is a semisolid preparation containing the drug, liquid and a gelling agent like carbomer and tragacanth. Few gels like sodium alginate gel is used as ointment bases.

Examples: Aluminum hydroxide gel, bentonite gel, pilocarpine eye gel

8 Jellies

These are non-greasy, transparent or translucent semisolid preparations meant for external application to skin or mucous membrane.


  • Jellies for medication – Local anaesthetic antiseptics
  • Jellies for lubrication – Tragacanth

9 Inhalants.

Inhalant is a liquid that contains a single drug or a mixture of drugs that have high vapor pressure. An inhaler or nebulizer is used to administer the drug in the nasal passage where it elicits its effect. Examples: Propylhexedrine inhalation, amyl nitrite inhalation, menthol and eucalyptus inhalation. benzoin inhalation.

10 Aerosols

Aerosol is a pressurized system of drug and propellant within a container which is released through an orifice intended for local activity in the respiratory tract. Propellant helps to build up a proper pressure inside the cylinder and the dose can be controlled by different valves. Metered dose aerosols are used for accurate dose management.

Example: Ipratropium bromide, terbutaline sulfate.

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