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Types of Dosage Forms

Dosage forms are the means by which drug molecules are delivered to sites of action within the body.The different forms in which drugs may be supplied to a patient are described briefly in this section.

Types:
                  Implants
                  Insufflations
                  Irrigation Solutions
                  Linctuses
                  Liniments
                  Lotions
                  Lozenges
                  Mixtures
                  Mouthwashes
                  Nasal Drops and Sprays
                  Ointments
                  Oral Emulsions
                  Oral Liquids
                  Paints
                  Parenteral Preparations (Injectable Preparations)
                  Pastes
                  Pills
                  Poultices
                  Powders (Oral)

Implants
These are sterile disks or cylinders introduced surgically into body tissues and designed to release one or more medicaments over an extended period of time.

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Insufflations
These are medicated powders designed to be blown into the ear, nose, throat or body cavities by means of a device known as an insufflator. Bulk insufflation has largely disappeared and has been replaced by individual doses of powdered drugs supplied in hard capsules and inhaled from a device which breaks the capsule and allows the patient to inhale the powder. This type of insufflation is used mainly for drug delivery into the respiratory tract by inhalation.

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Irrigation Solutions
These are sterile, pyrogen-free solutions usually intended for irrigation of body cavities, operation cavities, wounds or the urogenital system.

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Linctuses
Linctuses are viscous, liquid oral preparations that are usually prescribed for the relief of cough. They usually contain a high proportion of syrup and glycerol which have a demulcent effect on the membranes of the throat. The dose volume is small (5ml) and, to prolong the demulcent action, they should be taken undiluted.

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Liniments
Liniments are fluid, semi-fluid or, occasionally, semi-solid preparations intended for application to the skin. They may be alcoholic or oily solutions or emulsions. Most are massaged into the skin (counter-irritant or stimulating types) but some are applied on a warm dressing or with a brush (analgesic and soothing types). Liniments should not be applied to broken skin.

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Lotions
These are fluid preparations for external application without friction. They are either dabbed on the skin or applied on a suitable dressing and covered with a waterproof dressing to reduce evaporation.

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Lozenges
Lozenges are solid preparations consisting of sugar and gum, the latter giving strength and cohesiveness to the lozenge and facilitating slow release of the medicament. They are used to medicate the mouth and throat and for the slow administration of indigestion or cough remedies.

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Mixtures
Mixtures are liquid oral preparations consisting of one or more medicaments dissolved or suspended in an aqueous vehicle. Official mixtures are not usually formulated for a long shelf-life.

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Mouthwashes
These are similar to gargles but are used for oral hygiene and to treat infections of the mouth.

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Nasal Drops and Sprays
Drugs in solution may be instilled into the nose from a dropper or from a plastic squeeze bottle. The drug may have a local effect, e.g. antihistamine, vasoconstrictor, decongestant. Alternatively the drug may be absorbed through the nasal mucosa to exert a systemic effect, e.g. the peptide hormones oxytocin and vasopressin.
The use of oily nasal drops should be avoided because of possible damage to the cilia of the nasal mucosa. Prolonged use of nasal vasoconstrictors may result in rebound vasodilatation and further nasal congestion.

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Ointments
Ointments are semi-solid, greasy preparations for application to the skin, rectum or nasal mucosa. The base is usually anhydrous and immiscible with skin secretions. Ointments may be used as emollients or to apply suspended or dissolved medicaments to the skin. Ointments intended for application to large open wounds should be sterile.

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Oral Emulsions
The term 'oral emulsion' as an oral dosage form may be defined as 'a fine dispersion of droplets of an oily liquid in an aqueous liquid which forms the continuous phase'. Drugs may be dissolved in either of the phases or suspended in the emulsion.

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Oral Liquids
Oral Liquids are homogeneous preparations containing one or more active ingredients dissolved or suspended in a suitable vehicle. Elixirs, linctuses, mixtures, oral drops, oral emulsions, oral solutions and oral suspensions are included in the general category of oral liquids.

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Paints
Paints are liquids for application to the skin or mucous membranes. Skin paints often have a volatile solvent that evaporates quickly to leave a dry resinous film of medicament. Throat paints are more viscous due to a high content of glycerol, designed to prolong contact of the medicament with the affected site.

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Parenteral Preparations (Injectable Preparations)
These are sterile dosage forms containing one or more medicaments and designed for parenteral administration.
Injections are sterile solutions, suspensions or emulsions in a suitable aqueous or non-aqueous vehicle and are usually classified according to their route of administration.
Powders for injections are sterile solid substances to be dissolved or suspended by adding a prescribed volume of the appropriate sterile fluid. The solution or suspension is usually prepared immediately prior to use to avoid deterioration of the product on storage.
Intravenous infusions are sterile aqueous solutions or emulsions, free from pyrogens and usually made isotonic with blood. they do not contain added antimicrobial preservatives or buffering agents and are designed for intravenous administration in volumes usually greater than 10-15 ml.

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Pastes
Pastes are semi-solid preparations for external application that differ from similar ointments and gels in that they contain a high proportion of finely powdered medicaments. The base may be anhydrous (liquid or soft paraffin) or water soluble (glycerol or a mucilage). Their stiffness makes them useful protective coatings. Pastes intended for application to large open wounds should be sterile.

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Pills
Pills are oral dosage forms which consist of spherical masses prepared from one or more medicaments incorporated with inert excipients. Pills are now rarely used. The term 'pill' is used colloquially (yet incorrectly) as a synonym for oral contraceptive tablets which are actually prepared by compression.

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Poultices
Poultices are paste-like preparations used externally to reduce pain and inflammation because they retain heat well. After heating, the preparation is spread thickly on a dressing and applied as hot as the patient can bear, to the affected area.

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Powders (Oral)
There are two kinds of powder intended for internal use.
Bulk Powders usually contain non-potent medicaments such as antacids since the patient measures a dose by volume using a 5ml medicine spoon. The powder is then usually dispersed in water or, in the case of effervescent powders, dissolved before taking.
Divided Powders are packaged individually - each dose is seperately wrapped in paper or sealed into a sachet.

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