Drugs can be used for diagnosis, prevention or treatment of diseases. To achieve any of these functions, the drug will be used on the body- local application or internally –systemic application. No matter where the drug is used to achieve the desired effect the form the drug is prepared matters.
Generally, drugs can come inform of;
Solid
Liquid
Gases
There are some factors to be considered before any of these forms are chosen for a drug. These factors include;
Protection of the drug against destruction from sunlight, moisture or atmospheric oxygen.
Protection against distruction from stomach acid. If the drug is to be given orally before the target organ.
To cover up foul odor or bitter tastes of the drug.
To provide enough protection for a sustained released action.
SOLID DOSAGE FORM
As the name implies drugs are made to assume a fixed shape or volumes.
They include:
Tablet: They are produced by compressing or moulding into different shapes and sizes. They may appear in different colors and shapes. They may also be coated to mask some odor or bitter taste and are usually swallowed with water unless otherwise instructed as in suppositories.
Lozenges (Troches): They are made to be slowly released while holding in the mouth Mostly used for treatment of sore throat, cough and in some form of indigestion.
Pessaries: They are medicated preparations made to be inserted into the vagina where they dissolve or melt to produce a local effect.
Pill: They are oral dosage forms that are made in powdered form but held with adhesive substances. They are spherical, ovoid and usually sugar coated. However, they have been replaced with tablets and capsules.
Granules/Effervescent granules: This is a convenient way to administer some drugs with unpleasant tastes. The active substance mixed with sugar, flavouring agents and other substances are granulated by passing through sieves. They are packed into a single dosage units.
In some cases the active medicament is mixed with sodium bicarbonate, tartaric acid, saccharin or sucrose as sweetening agent. The sodium bicarbonate and tartaric acid added helps to generate an effervescent reaction when dissolved in water. Hence, they are called effervescent granules.
Dusting powder: These are free flowing solid medicaments used for external application.
Pastes: They are semi – solid preparations for external applications as protective coatings.
Pastilles: These are similar to lozenges but softer.
Poultices: These are paste- like substances that are applied externally to reduce inflammation because they can retain heat well. They are spread on dressing and applied on the inflamed surface.
Capsules: These are small containers usually made from gelatin. They are used to deliver drugs of different types. There are hard one meant for solid medicaments and soft (flexible) type for solid, semi-solid and liquid medicaments. They can also be made to resist acid destruction in the stomach and will be used to deliver the medicaments to intestines before the contents are released after dissolving in alkaline juice. Some can deliver the drugs in the stomach when in contact with the acidic juice in the stomach. In some cases they may be used to deliver drugs to rectum or vagina.
Ointments: These are semi-solid preparations for application to the skin, rectum, and nasal mucosa. The anhydrous base contains the medicament in solution or suspension.
LIQUID DOSAGE FORM
Liquid is a fluid that has a definite volume but not definite shape in spite of pressure.
It is incompressible and takes the shape of the container.
In preparing a liquid dosage drug, the active medicine(s) is dissolved in water to form aqueous solution.
In some cases the active substance is dispersed in water to form aqueous suspension. Here the substance is suspended in the solution by suspending agent and needs proper shaking before use,
In general drug can appear in liquid form for oral use, injection and topical application.
DIFFERENT TYPES OF LIQUID DOSAGE FORM.
Syrup: This is liquid oral preparation in which the vehicle is normally a concentrated aqueous solution which is made by adding solution of sucrose or other solution of sugar to water.
Elixir: This is a clear liquid, oral preparation of potent or nauseous drugs. There can be flavoured and attractive colour added. They are hydro – alcoholic in nature and meant for oral use. They contain water and alcohol as solvents to dissolve the active ingredients when water alone cannot dissolve it.
Enemas: These are solutions, suspensions, or oil in water emulsion of medicaments which are intended to be used for rectal treatment.
Emulsions: it is well known that oil and water do not mix. However, to make oil or fat pleasant enough for oral use, this type of liquid preparation is made by dissolving oil into water through the use of emulsying agent which decreases the force between the two interface thereby allowing the oil to stay in the water as a pleasantly liquid oral preparation.
Gargles: These are aqueous solution that can be used to prevent or treat throat infection.
Inhalations: Here the liquid preparation contains volatile substances. They can be used to relieve congestion and inflammation of the respiratory tract.
Gels: These are aqueous colloidal suspensions of hydrated form of insoluble medicaments e.g antacid liquid preparations.
Linctuses: They are solutions or admixtures containing high quantity of syrup and sometimes, glycerin, which gives a sweet taste and a demulcent effect on the mucous membrane of the throat. They are viscous, liquid oral preparations and effective for relief of cough.
Lotions: These are fluid preparations for external use without friction. They may be either dabbed on the skin or applied on a suitable dressing and covered with water- proof materials to reduce evaporation.
Mixtures: They are common form of liquid oral preparation. Here the vehicle is usually aqueous and the active ingredients may be in solution or suspension.
Mouthwashes: They are also aqueous preparations just like gargles but are used for oral hygiene and mouth infections.
Nasal Drops: These are aqueous solutions that are instilled inside the nose with a dropper.
Eye Drops: These are aqueous solutions that are instilled into the eyes with a dropper.
Ear Drops: They are aqueous solutions that are instilled inside the ears with a dropper.
Magmas: These are suspension of poorly soluble substances in water to form bulky suspensions which resemble milk as they can be white in colour. Gels and Magmas resemble except that the particles in Magma are larger. As a result particles in magma may separate on standing and must be shaked before use to maintain uniformity of active ingredients.
Spirits: These are alcoholic or aqueous – alcoholic solutions of volatile substances. Some are medicinal while some may be used as flavouring agents.
Sprays: These are preparations involving drugs in aqueous, alcoholic or glycerin containing media. They are used in nasal mucosa or throat through atomizer or nebulizer as in aerosols inhalers.
Liniment: This is a fluid, semi-fluid or semi-solid preparation meant for application to the skin. It can be alcoholic or oily solution or emulsion. It is massaged into the skin as counter-irritant or stimulating types or used on a warm dressing or with a brush inform of analgesic and soothing types. It is not meant for broken skin.
GASEOUS DOSAGE FORMS.
These are drugs that are packed in a container which are released when pressure is applied in order to deliver, the active ingredients to the target organs. The gas inside contains active ingredients. The containers are built with valves which continuously deliver the desired drug quantity. This form of dosage formulation can be used to deliver drug on skin and into nose and mouth. Since the preparation is in gaseous form, it acts very fast.
Examples of gaseous dosage preparations are sprays, vaporizer, Aerosols, Nebulizer and atomizers, inhalers, insufflations.
NOTE:
Insufflations are special preparation of dusting powder that are blown into a specific part of the body especially cavities for medical purpose using a special designed instrument called insufflator.
Nebulizer – This is a special instrument designed to change a liquid medication into a mist so that one can inhale it in the lungs
Atomizer – This is a special instrument that can release water or other liquids as a fine spray or vapor.
Inhaler – An instrument used in administering drugs that can be breathed in e.g. asthmatic drug.
Aerosols – These are shortened version of aerosolutions which means the suspension of solid particles or liquid droplets in the air or another gas.
Vaporizer – An instrument that can turn a substance into a vapor or gas especially for a inhalation as in medicine.
ACKNOWLEDGEMENT
Geneith Pharm. Ltd.
Wikipedia
WEBMD
Cooper and Gunn’s Dispensing For Pharmaceutical Students, Edited by S J Carter.