Capsule formulations dosage forms

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. 

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]. 

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. 

Dissolution characteristics of solid dosage forms, which depend on formulation in addition to the properties of the chemical itself (e.g., vehicle may decrease permeability of suspension or capsule to water and retard dissolution and diffusion). 

Currently, the Japanese Pharmacopoeia (JP) is the only pharmacopeia that requires a specific sinker device for all capsule formulations. The USP recommends a few turns of a nonreac-tive material wire when the dosage form tends to float (12) (see Chapter 2 for illustrations of the Japanese and USP sinkers). Because sinkers can significantly influence the dissolution... 

Suspensions are two-phase systems consisting of a finely divided solid dispersed in a liquid, solid, or a gas (Table 6). They are appropriate when the drug to be incorporated is not sufficiently soluble in an ordinary solvent or cosolvent system. They are used orally and topically. Examples of compounded suspensions include pediatric oral liquids where a commercial pediatric dosage form is not available. Commercial tablets and capsules are formulated into a vehicle and can be individually flavored to the patient s preference. 

Excipients are sub-divided into various functional classifications, depending on the role that they are intended to play in the resultant formulation, for example, fillers, disintegrants, binders, lubricants and glidants. An added complexity is the fact that certain excipients can have different functional roles in different formulation types. Thus, lactose is widely used as a filler or diluent in solid oral dosage forms, for example, tablets and capsules [2] and as a carrier for inhalation products [3]. 

There are few occasions where a drug is delivered alone in a pure form into the body, but it is usually combined with other materials (called excipients) to form drug delivery systems ( medicines , formulations or dosage forms ). These promote accurate dosing, therapeutic effectiveness, stability and patient acceptability. By far the most common route for delivering drugs into the body is by the oral route, swallowing a tablet or capsule. 

St. John s wort and some individual constituents of the preparations have been administered orally, topically, and intravenously in various pharmaceutical formulations, including tinctures, teas, capsules, purified components, and tablets. These botanical preparations of St. John s wort are prepared from plant components (i.e., flowers, buds, and stalk) whose content of the wide array of structurally diverse bioactive constituents may differ (Table 1 and Fig. 2). Many commercial tablet and capsule formulations of St. John s wort are standardized using the ultraviolet absorbance of the naphtho-dianthrones, hypericin, and pseudohypericin, to contain 0.3% hypericin content. Thus, a 300 mg dose of St. John s wort contains approximately 900 pg hypericin per dose. Despite the standardization of dosage forms... 

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