A drug may be defined as an agent, intened for use in the diagonosis, mitigation, treatment, cure or prevention of disease in man or in other animals. Drugs are rarely administered in their original pure state. They are administered in different dosage forms after converting them in to a suitable formulation. Every dosage form is a combination of the drug and different kind of non-drug components called “additives”.the additives are used to give a perticular shape to the formulation to increase its stability and also to increase its palatability as well as to give more elegance to the preparation.
Important Dosage Forms
Transformation of drug into different dosage forms is done for the following resons are
1. To protect the drug substance form oxidation, hydrolysis, and reduction.
Example:-coated tablets and sealed ampoules.
2. To protect the drugs form the destructive effect of gastric juice of the stomach after oral administration.
Example:-enteric coated tablets.
3. To provide a safe and convenient delivery of accurate dosage.
4. To conceal the bitter,salty or obnoxious taste or ordur og a drug substance.
Example:-capsule,coated tablets and flavoured syrups etc.
5. To provide for the optimum drug action through inhalation therapy.
Example:-inhalation aerosols and inhalants.
6. To provide for the insertion of the drug in to one of the body cavities.
Example:-rectal or vaginal suppositories
7. To provide form the maximum drug action form topical administration sites .
example:-creams,ointments,ophthalmic preparation and E.N.T. preparation.
8. To provide sustained released action through controlled released mechanism.
Example:-sustained released tablets, capsules and suspensions.
9. To provide liquid dosageform of the drugs soluble in a suitable vehicle.
10. To provide liquid preparation of the drugs which are insoluble or unstable in different vehicles.
11. To provide the drugs within body tissues.
12. Many dosage forms can be easily identified form their distinct colour,shape or identifying markings.
The dosages are divide in three forms
a. Solid dosage forms
b. Liquid dosage forms
c. Semi-solid dosage forms
Solid Dosage Forms
The solid dosage forms are available mostly in unit dosage forms such as tablets,capsule,pills,cachets or powders.When drugs are to be administered orally in dry state,tablets and capsules are yhe most convenient dosage form.They are effective and patients have no problem in their handling,identification and administration.Some solids are packed and supplied in bulk.The bulk forms meant for internal use are supplied either as garnules or fine powder.the bulk powders meant for external use are dusting powders,insufflations,snuffs and tooth powders.
These are meant for external application ti the skin and generally applied in a very fine state of subdivision to avoid local irritation.Hence,dusting powders should be passed through a 80 sieve to enhance their effectiveness.
These are medicated dusting powders meant for introduction into the body cavities such as nose,throat,ears and vagina with the help of an apparatus known as “Insufflator”.It sparys the powder into a stream of finely divided particles all over the site application.
Yhese are finely divided solid dosage forms of medicament are inhaled into nostrils for its antiseptics,bronchiodilator and decongestion action.
These are solid dosage forms of medicament or medicaments which are prepared by moulding or by compression.Certain excipients are also added to the medicaments in the formulation of tablets
The capsule are solid unit dosage form in which one or more medicaments and inert substances are enclosed within a small shell,generally prepared from a suitable form of gelatin.
Pills are small, rounded solid dosage forms containing medicament and are intended to be administered orally.The medicameents are mixed with excipients to form a firm plastic mass.the mass is rolled uniforms pill pipe,which is cut into a number of pills.These are rounded to form pills of uniform size and shape.
Liquid Dosage Forms
Liquid stage forms are meant for internal,parenteral or external use.Example,syrups,elixirs,drops.
simple syrup is a saturated solution of sucrose in purified water.The concentration of suger is 66% w/w.The syrups are sweet viscous preparations.The syrups containing medicinal substances are called “Medicated syrups” and those containing aromatic or flavoured substances are known as “Flavoured syrups”.
Elixirs are sweet aromatic preparation and are usually coloured.The main ingredients of elixirs are ethyl alcohol(4-40%),water,glycerin or propylene glycol,flavouring agent,surup and some suitable preservative.The medicated elixirs usually contain some very potent drug,such as antibiotics,antihistamines or sedatives.The flavouring elixirs are used as flavours vehicles.
These are liquid preparations meant for oral administrations.The oil soluble vitamins,such as vitamin A and D concentrates in fish-livor oil are presented as drops for administrations. Since these preparations contain potent medicaments,the dose must be measured accurately.
Semi-sold Dosage Forms
Semi-solid dosage forms are mainly meant for exrernal application.Example,Ointments.creams
Ointments are semi-solid preparations meant for application to the skin or mucous membrance.They usually contain a medicament or medicaments dissolved,suspended or emulsified in the ointment base.The ointments are mainly used as protective or emollient for the skin.The ointments which are meant for application to the eye are called “Ophtgalmic Ointments”.These ointments are sterile and free from irritation.
These are viscous semi-solid emulsions which are meant for external use. The creams are of two types,aqueous and oily creams.In case of aqueous creans, the emulsions are in oil-in-water type and in case of oily creams, emulsions are water in oil type.The oil-in-water type cream is relatively non-greasy.In aqueous creams,the emulsifying anionic,cationic and non-ionic waxes,polysorbates and triethanolamine soaps are used as emulsifying agent.The oily creams are generally prepared with emulsifying agent,such as wool fat, wool alcohols, beeswax and calcium soaps.A suitable preservative is generally added in aqueous creams which have the tendency to bacterial and fungal growth.