Second Level Pharmacy Students Pharmaceutical Dosage Forms 2 Germeen N.S. Girgis Lecturer of Pharmaceutics Faculty of Pharmacy Mansoura University

The course include Tablets Capsules Ointments Pastes

Tablets

Scope Definition Advantages and disadvantages of tablets. Types of tablets. Tablet Ingredients. Tablet manufacture. Problems during tableting. Quality control of tablets.

Tablets are probably the most popular dosage form. Tablet is defined as a solid dosage form containing medicaments with or without suitable excipients. They may be classified according to the method of manufacture into compressed tablets and molded tablets.

amount of medicinal substances They vary in shape and differ greatly in size and weight, depending on: amount of medicinal substances the intended mode of administration.

Compressed tablets Compressed tablets are prepared by single compression using tablet machines. After a quantity of powdered or granulated tableting material flow into a die, the upper and lower punches of the tablet machine compress the material under a high pressure.

Molded tablets Molded tablets are prepared by forcing dampened tablet material into a mold of any shape. The formed tablet is then ejected from the mold and allowed to dry. Molding is generally reserved for laboratory and small-scale production.

Most of tablets are used for: Systemic drug delivery, so drug must be dissolved, released, and then absorbed in the systemic circulation. Local delivery, tablets can be formulated for local effects of the drugs in the mouth or GIT, or to increase pH of stomach.

Advantages of tablet dosage form 1) They are unit dosage form and offer the greatest capabilities of all oral dosage form for the greatest dose precision and the least content variability.

Also, whenever a fractional dose is required, tablets are divided into halves and quarters by drawing lines of tablet.

4)Easiest and cheapest to package and ship. 5) Easy to swallowing. 2) The manufacturing cost of tablets is low as compared to other dosage forms. 3) Lighter and compact. 4)Easiest and cheapest to package and ship. 5) Easy to swallowing.

6) Objectionable odour and bitter taste can be masked by coating technique. 7) Sustained release product is possible by enteric coating.

8)Suitable for large scale production. 9)Greatest chemical and microbial stability over all oral dosage form. 10)Tablets are attractive and elegant in appearance. 11)Product identification is easy and rapid.

Disadvantages of tablet dosage form 1. Difficult to swallow in case of children and unconscious patients. 2. Some drugs resist compression into dense compacts, owing to amorphous nature, low density character. 3. Poor bioavailability of poorly water soluble drugs or poorly absorbable drugs. Drugs with poor wetting - slow dissolution properties - optimum absorption high in GIT may be difficult to formulate or manufacture as a tablet of a full drug bioavailability.

4. Bitter tasting drugs, drugs with an objectionable odor or drugs that are sensitive to oxygen may require encapsulation or coating. In such cases, capsule may offer the best and lowest cost. 5. Drugs that are liquid in nature are difficult to formulate as tablets.

General Properties of Tablet Dosage Form A tablet should have elegant product identity while free of defects like chips, cracks, discoloration, and contamination. Should have sufficient strength to withstand mechanical shock during its production packaging, shipping and dispensing. Must have accurate dosage of medicament. Should have physical stability to maintain its physical attributes over time. Must have chemical stability over time so as not to follow alteration of the medicinal agents. The tablet must be able to release the medicinal agents in a predictable and reproducible manner.

Types of Tablets Tablets ingested orally. Tablets used in oral cavity. Tablets administered by other route. Tablets used to prepare solution.

1) Tablets ingested orally Compressed Multiple compressed Repeat action Delayed release Sugar coated Film coated Chewable tablet

Compressed Tablets Standard uncoated tablets are manufactured by compression. The general methods of preparation are by wet granulation, dry granulation or direct compression. Both type of action – systemic effect and local effect.

Multiple Compressed Tablets For incompatible components. A) Layered tablet either two layered (for two components) or three layered (for three components) tablet. B) Compressed coated type- either tablet within a tablet or tablet within a tablet within a tablet. The inner tablet being the core and the outer portion being the shell.

MULTIPLY COMPRESSED TABLETS

Reasons for preparing Multiple compressed tablets Tablets in this category are usually prepared for two reasons: 1. To separate physically or chemically incompatible ingredients. 2. To produce repeat action or prolong action product.

Delayed action and enteric-coated tablets Enteric-coated tablets have delayed-release features. This dosage form is designed to pass unchanged through the stomach to the intestine, where the tablets disintegrate and allow drug dissolution and absorption.

Most enteric coatings are stable at the highly acidic pH found in the stomach, but breaks down rapidly at a less acidic (relatively more basic) pH. For example, they will not dissolve in the acidic juices of the stomach (pH ~3), but they will dissolve in the alkaline (pH 7-9) environment present in the small intestine.

Enteric coatings are employed when: the drug substance is destroyed by gastric acid or the drug substance is particularly irritating to the gastric mucosa or when bypass of the stomach substantially enhances drug absorption. All enteric coated tablets are type of delayed action tablet but all delayed action tablets are not enteric or not intended to produce enteric action.

Sugar coated tablet Primary role is to produce an elegant, glossy, easy to swallow tablet. Such coatings may be colored and are beneficial in: covering up drug substances having objectionable tastes or odors, and in protecting materials sensitive to oxidation. It is widely utilized in preparing multivitamin and multivitamin mineral combination.

SUGAR-COATED TABLETS

Film coated tablet Film-coated tablets are compressed tablets coated with a thin layer of a polymer capable of forming a skin like film. The film is usually colored and has several advantages over sugar-coatings in that it is more durable, less bulky, and less time period required for coating operation.

FILM-COATED TABLETS

Chewable tablet These are intended to be chewed in the mouth before swallowing. Bitter tasting drugs are not suitable for this type tablet. Chewable tablets are prepared mainly by wet granulation and compression. Chewable tablets disintegrate rapidly when chewed or allowed to dissolve in the mouth.

They are especially useful in tablet formulations for children and are commonly employed in the preparation of multiple vitamin tablets. They are also used in the administration of antacids and antiflatulents (to remove excessive amount of gas in the stomach and intestines).

2) Tablets used in oral cavity Buccal and sublingual tablet Troches and lozenges Dental cone

Buccal and Sublingual Tablets These tablets are small, flat and are intended to: be held between the cheek and teeth or in cheek pouch (buccal tablet) or below the tongue (sublingual tablet) for absorption through the oral mucosa.

They enable oral absorption of drugs that are destroyed by the gastric juice and/or are poorly absorbed from the gastrointestinal tract. Buccal tablets are intended to be dissolved in the buccal pouch, and are designed to erode slowly, whereas those for sublingual use (such as nitroglycerin) dissolve promptly and provide rapid drug effects.

lozenges Lozenges are disc-shaped solid dosage forms containing a medicinal agent and generally a flavoring substance in a hard candy or sugar base. They are intended to be slowly dissolved in the oral cavity, usually for local effects, although some are formulated for systemic absorption.

3) Tablets administered by other route Implantation tablets Vaginal tablets

Vaginal Tablets Implantation Tablets (Pellets) They are designed for subcutaneous implantation to provide prolonged drug effect from one month to a year. Tablets are pear shaped, used as antibacterial, antiseptic and astringent to treat vaginal infection Vaginal Tablets

4) Tablets used to prepare solution Effervescent tablets Dispensing tablets Hypodermic tablets Tablet triturates