Tablet formulations dosage forms

Compressed Tablets. This popular type of dosage form offers convenience, stabiUty, accuracy and precision, and good bioavadabihty of active ingredients. After the best formulation has been estabflshed, compressed tablets can be manufactured at high rates of speed on advanced equipment. Tablets can be made to achieve rapid dmg release or to produce delayed, repeat, or prolonged therapeutic action (Controlled release technology, pharmaceutical). ... 

Uses. Aspirin has analgesic, antiinflammatory, and antipyretic activity. It is used for the reHef of less severe types of pain, such as headache, neuritis, acute and chronic rheumatoid arthritis, and toothache. Aspirin can be purchased in a variety of OTC and prescription dosage forms made and formulated by many companies. Tablets, ie, buffered, plain, or enteric-coated, are the most familiar in the United States, but other forms such as powder and effervescent formulations are of considerable importance in other parts of the world. 

Some antihistamines such as diphenhydramine, dimenhy-drinate, and meclizine are available without a prescription, making self-treatment convenient for patients. Antihistamines are available in a variety of dosage forms, including oral capsules, tablets and liquids. Liquid formulations are convenient for children or adults who are unable to swallow solid dosage forms. 

Some tablets combine sustained-release and rapid disintegration characteristics. Products such as K-Dur (Key Pharmaceuticals) combine coated potassium chloride crystals in a rapidly releasing tablet. In this particular instance, the crystals are coated with ethylcellulose, a water-insoluble polymer, and are then incorporated into a rapidly disintegrating microcrystalline cellulose (MCC) matrix. The purpose of this tablet is to minimize GI ulceration, commonly encountered by patients treated with potassium chloride. This simple but elegant formulation is an example of a solid dosage form strategy used to achieve clinical goals. 

Most formulations are composed of one or more medicaments plus a variety of excipients. Irrespective of the type of tablet, general criteria for these raw materials are necessary. In order to produce accurate, reproducible dosage forms, it is essential that each component be uniformly dispersed within the mixture and that any tendency for component segregation be minimized. In addition, the processing operations demand that the mixture be both free-flowing and cohesive when compressed. 

Soft gelatin capsules are not an inexpensive dosage form, particularly when compared to direct compression tablets [3]. There is a more intimate contact between the shell and its liquid contents than exists with dry-filled hard gelatin capsules, which increases the possibility of interactions. For instance, chloral hydrate formulated with an oily vehicle exerts a proteolytic effect on the gelatin shell however, the effect is greatly reduced when the oily vehicle is replaced with polyethylene glycol [3]. 

As the list of applications illustrates, the techniques of optimization are not limited to tablets or even to solids. Any dosage form and any process should be amenable to this type of experimentation and analysis. From the most simple formulation to the most complicated one, there are ingredient levels and processing steps that can be varied, and any information on the result of such variation should be useful to the formulator. 

Product bioavailability is mentioned, especially where it is low. Where there are differences between the formulations tested for bioavailability during the development process and the formulation to be marketed, there is considerable discussion of the data provided on the bioequivalence of the different products and/or formulations. This is particularly so where, for example, early clinical studies were undertaken with capsules but the marketed dosage form is to be a tablet. Bioequivalence data and pharmacokinetic data (e.g., in crossover studies) and comparative dissolution studies are usually reported. This is particularly significant where the different strengths of the final products are not achieved by using different quantities of the same granulate formulation. Process optimization may also be addressed in such cases. 

The dosage forms most commonly employed for pediatric formulations are liquids and chewable tablets. A perceived unpleasant taste is much more evident with these dosage forms than when a drug is administered as a conventional solid oral dosage form. Second, it is widely believed that children younger than the age of 6 years have more acute taste perception than older children and adults. Taste buds and olfactory receptors are fully developed in early infancy. Loss of taste perception accompanies the aging process. 

Solid oral dosage forms, particularly tablets, are the preferred type of formulation in the United States. Not only are these products widely accepted by consumers, but they are also relatively cheaper to develop and manufacture than oral liquids or suspensions, par-enterals, or suppositories. Figure 4 shows, quite clearly, that even the elderly primarily make use of solid oral dosage forms [162]. 

Chewable Tablets. It has already been noted that most elderly patients experience a decrease in their ability to chew efficiently [125,137,138,143]. Therefore, by virtue of their design, chewable tablets are not often recommended for use by elderly patients (particularly those who are edentulous) 155-163,164], Most chewable formulations also rely on an adequate amount of chewing action to obtain full release of their ingredients (e.g., chewing promotes the foaming action provided by some chewable antacid products). So, aside from being difficult form the elderly patient to use, full benefit of a chewable dosage form may not be achieved by these patients. Additionally, the use of chewable tablets by denture wearers may cause local irritation in the oral cavity [155]. 

Studies involving instrumented compaction equipment can be extremely useful in the development of dosage forms, especially when the amount of drug substance is limited in quantity. Marshall has described a program in which dynamic studies of powder compaction can be used at all stages of the development process to acquire formulation information [63]. The initial experiments include a determination of the intrinsic compactability of the compound. In subsequent work, simple tablets are prepared, and tested for dissolution, potency, and content uniformity. Through studies of the compaction mechanism, it becomes possible to deduce means to improve the formulation under study. 

July 2002, Wyeth Pharmaceutical discontinued manufacturing cefixime, at the time of publication, Lupin, Ltd, which has FDA approval to market cefixime, had marketed only a suspension formulation of the drug and not the 400-mg tablet dosage form. Another recommended IM or po cephalosporin also can be used. 

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