DRUG DOSAGE FORMS; Capsules, Tablets and Injections

CAPSULES

In the manufacturing of pharmaceuticals, encapsulation refers to a range of techniques used to enclose medicines in a relatively stable shell known as a capsule, allowing them to be taken orally. Capsules are solid dosage form containing one or more medicinal substances enclosed with in a small shell or container prepared from suitable form of gelatin. They are of two types

Hard gelatin capsules: The basic empty capsule shells are made up of the mixture of the gelatin, sugar and water. They are physically hard. The capsules are made in two parts by dipping metal pins in the gelling agent solution. Before use, the two halves are separated, the capsule is filled with powder or more normally pellets made by the process of Extrusion & Spheronization (either by placing a compressed slug of powder into one half of the capsule, or by filling one half of the capsule with loose powder) and the other half of the capsule is pressed on. With the compressed slug method, weight varies less between capsules.

Soft gelatin capsules: These are prepared from shells of gelatin to which glycerin or polyhydric alcohols such as sorbitol are added to render the gelatin elastic or plastic like. Soft gelatin capsule can be an effective delivery system for oral drugs, especially poorly soluble drugs. This is because the fill can contain liquid ingredients that help increase solubility or permeability of the drug across the membranes in the body. Liquid ingredients are difficult to include in any other solid dosage form such as a tablet. Soft gelatin capsules are also highly suited to potent drugs, where the highly reproducible filling process helps ensure each Soft gelatin capsule has the same drug content, and because the operators are not exposed to any drug dust during the manufacturing process. Advantages are that they are easily swallowed due to tasteless shell. Volatile drug substances and hygroscopic drugs are better suited in soft gelatin capsules.

TABLETS

Tablet is a mixture of active substance and excipient, usually in powder form, pressed or compacted from a powder into a solid dose. The excipients can include diluents, binders or granulating agents, glidants (flow aids) and lubricants to ensure efficient tabletting; disintegrants to promote tablet break-up in the digestive tract; sweeteners or flavors to enhance taste; and pigments to make the tablets visually attractive. A polymer coating is often applied to make the tablet smoother and easier to swallow, to control the release rate of the active ingredient, to make it more resistant to the environment (extending its shelf life), or to enhance the tablet's appearance. The compressed tablet is the most popular dosage form in use today. About two-thirds of all prescriptions are dispensed as solid dosage forms, and half of these are compressed tablets. A tablet can be formulated to deliver an accurate dosage to a specific site; it is usually taken orally, but can be administered sublingually, buccally, rectally or intravaginally. Medicinal tablets were originally made in the shape of a disk of whatever color their components determined, but are now made in many shapes and colors to help distinguish different medicines. Tablets are often stamped with symbols, letters, and numbers, which enable them to be identified. Sizes of tablets to be swallowed range from a few millimeters to about a centimeter. Some tablets are in the shape of capsules, and are called "caplets". Medicinal tablets and capsules are often called pills. A pill is a small, round, solid pharmaceutical oral dosage form that was in use before the advent of tablets and capsules. Pills were made by mixing the active ingredients with an excipient such as glucose syrup in a mortar and pestle to form a paste, then rolling the mass into a long cylindrical shape and dividing it into equal portions, which were then rolled into balls, and often coated with sugar to make them more palatable.

Types of tablet

Immediate release tablets: The dosage form is designed to release the drug substance immediately after ingestion.

Delayed release: The drug substance is not released until a physical event has occurred, e.g., time elapsed, change in pit of intestinal fluids, change in gut flora.

Chewable tablets: These are strong, hard tablets to give good mouth feel. For example Lozenges Strong. These tablets are prepared for local delivery to mouth or throat often prepared by a candy moulding process.

Buccal tablets: These are designed to be placed in buccal cavity of mouth for rapid action.

Sublingual tablets: These are placed under the tongue for rapid dissolution.

Effervescent tablets: These are taken in water; the tablet forms an effervescent, often pleasant-tasting drink.

Advantages of tablets are Cheapest to manufactured and easy to pack, product identification is sample, and specialized profile products such as enteric coated or delayed release product are available. Tablets have best combined properties of chemicals, mechanical and microbiological stabilities.

INJECTIONS

Injections/injectables refer to drugs taken via injection. An injection is an infusion method of putting drug into the body, usually with a hollow needle and a syringe. These are sterile pyrogen free preparations intended to be administered parenterally.

An ampoule is a small sealed single dose vial which is used to contain medicine that must be protected from air and contaminants. They are sealed by melting the thin top with an open flame, and usually opened by snapping off the neck. The space above the chemical may be filled with an inert gas before sealing. The walls of glass ampoules are usually sufficiently strong to be brought into a glovebox without any difficulty. A multi-dose vial is a vial of liquid medication intended for parenteral administration that contains more than one dose of medication. Advantages are, rapid response is obtained and can be used when patient is uncooperative, or unconscious and when drug is unaffected by other route.