Pharmaceutical Dosage Form and Drug Delivery System

Introduction

A drug delivery system or dosage form is defined as the various means through which a drug is made to reach the specific target site in the body to perform its therapeutic actions. It is designed in such a way as to facilitate the provision of the drug components to the target site.

Why is dosage form required?

The need for designing a dosage form arises for many reasons which are summarized as follows:

• To ensure the safe and easy delivery of the drug to the active site.
• To provide the accurate dosage of the drug.
• To protect a drug from the harmful atmospheric effects such as oxidation and moisture. Drugs vulnerable of being effected by harmful effects of atmosphere are coated with a suitable protective agent allowing it to retain its efficacy.
• To provide an insoluble or unstable drug in liquid preparation such as suspensions.
• To mask the bitter, salty or undesirable taste or odor of any drug components.
• To provide a soluble drug in liquid preparation such as solution.
• To provide extended/prolonged drug action through the mechanism of controlled release.
• To provide optional drug action from topical routes of administration. Such as ointments, creams, ophthalmic, ear and nasal preparations.
• To allow drug administration through a number of body cavities such as vaginal and rectal suppositories.
• To allow maximum drug action using inhalation.
• To allow ease of drug identification through distinctive color, shape or identifiable markings on different dosage forms.
• To allow the accurate administration of a specific amount of dosage of the drug.

Types of dosage forms

Different types of dosage forms designed to facilitate in the effective administration of a drug are as follows:

Solution

Solutions are dosage forms that are prepared by dissolving a fixed amount of active drug component into an aqueous or non-aqueous solvent.

Syrups

A syrup is a concentrated solution of sugar (for example sucrose) in water or any other aqueous medium. Syrup could be medicated or non-medicated depending on the presence or absence of a medicinal component.

Suspensions

A suspension is a dosage form prepared by dispersing a coarse, insoluble drug component into an aqueous or non-aqueous medium using a suspending agent, which reduces the surface tension between the two mediums and allows them to mix together

Emulsions

Emulsion is a dosage form prepared by using two immiscible liquids, one of which is uniformly distributed throughout the other in the form of tiny droplets. The system is made stable using a suitable emulsifying agent. The diameter of the particles present in dispersed phase ranges from 0.1 to 100 micrometer.

Elixirs

Elixirs are clear, pleasantly flavored, sweetened hydro alcoholic liquid preparations that are meant for oral use.

They are mainly used as flavoring agents or pharmaceutical solvents.

Douches

A douche is an aqueous preparation which i.e. intended to be used against a part or cavity of the body. It is normally used as a cleansing or antiseptic agent. Examples of douches include eye douches and pharyngeal douches.

Enemas

Enemas are liquid preparations injected into the body through anal route, to stimulate evacuation of bowel.

Dry mixtures

Many drugs such as antibiotics are produced in the form of powders due to their insufficient stability in aqueous medium. The powder in reconstituted by addition of specific amount of solvent, at the time of administration.

Ointments

Ointments are semisolid preparations intended for external use, on the skin or mucous membranes. Ointments may be medicated or non-medicated. They are primarily used for their protectant, emollient or lubricating activity. They are immiscible with the secretions of the skin

Creams

Creams are preparations meant for external use. They are miscible with the skin secretions and are used for therapeutic, protective and prophylactic purposes.

Gels

Gels are semisolid, three dimensional dosage forms characterized by dispersion of very small inorganic or large organic particles in an aqueous medium. The final product is given a jelly like consistency by the addition of a gelling agent.

Pastes

Pastes are semisolid preparations that are applied externally. They differ from creams in such a way that they have greater proportion of solid material, making them stiff and difficult to penetrate. They are used topically as protective agents.

Collodions

They are liquid preparations which contain pyroxylin, a nitrocellulose, in a mixture of ethyl ether and ethyl alcohol. They are usually used topically on the skin for the treatment of warts and corns. Applied on the skin with a brush, they form a layer of pyroxylin on skin, acting as a keratolytic agent.

Liniments

They are dosage forms prepared for external use as rubefacient and counter irritant. They are mixtures of various substances in oil, alcoholic solutions of soaps or emulsion.

Plasters

Plasters are solid or semisolid adhesive preparations intended to be applied on skin and provide prolonged contact at the site. They are prepared by spreading adhesive mass on the back of a paper, fabric, moleskin or plastic. Adhesive is made from rubber or resin.

Suppositories

Suppositories are solid dosage forms meant to be administered in any body cavity where they can melt, soften and dissolve. They produce localized drug action. Some may also produce systemic effects. Examples of suppositories are nasal, vaginal, urethral or rectal suppositories.

Ophthalmic preparations

Pharmaceutical preparations that are meant for topical application to the eye are called ophthalmic preparations. They are used to treat intraocular bacterial, fungal or viral infections in the eye or eyelids. They are also used in the treatment of infectious conjunctivitis or inflammation, increased intraocular pressure, glaucoma or dry eye.

Otic preparations

Pharmaceutical Preparations used inside, outside or around the ear are called otic preparations. They are used to treat the conditions of external and middle ear.

Nasal preparations

Nasal preparations such as nasal drops, nasal sprays or nebulizers, aerosols, gels etc. are those products that are administered through the nasal cavity.

Products of Oral hygiene

These are the products that are applied inside the oral cavity to maintain the hygiene of teeth, gums or oral cavity, in general. It not only keeps the mouth clean but also helps in maintaining oral health.

Aerosols

Aerosols are dosage forms kept under pressure which produces a fine mist of particles upon actuation.  Their administration is dependent on the functionality of the storage container.

Powders

They are dry and finely divided drug particles intended for both internal and external use.

Granules

Agglomerates of powders are called granules.  The irregularly shaped granules may have any mesh size depending upon their application.

Capsules

Capsules are solid dosage form containing the active drug encapsulated inside a soft or hard shell or gelatin. They shell protects the drug from the acidic environment of the stomach.

Tablets

Tablets are solid dosage forms in which the active drug component is mixed with the excipient and compressed under high pressure. Tablet may be used orally, sublingually, buccally or vaginally.

Parenterals

Parenterals are sterile, pyrogen-free pharmaceutical preparations intended to be injected into the body.