Tablet formulations glidants

The section on flowability discussed the role of glidants in tablet formulation. Glidants are one of three interrelated types of lubricant employed in solid dosage form manufacture. The two other classes of lubricant are antiadherent excipients, which reduce the friction between the tablet punch faces and tablet punches, and die-wall lubricant excipients, which reduce the friction between the tablet surface and the die wall during and after compaction to enable easy ejection of the tablet. 

To motivate the response surface approach, suppose that there is some response of interest (for example, crushing strength in the tablet formulation example of Section 2.1.1), and a set of quantitative, continuous design variables that are of interest to the researcher (for example, the quantities of glidant, lactose, and disintegrant for the tablet formulation example). One possible objective for the researcher might be to understand and describe the relationship between the design variables and the response. This relationship can be described mathematically by... 

Cadila Laboratories Ltd. of Ahmedabad, India have developed an expert system for the formulation of tablets for active ingredients based on their physical, chemical, and biological properties. The system first identifies the desirable properties in the excipients for optimum compatibility with the active ingredient and then selects those that have the required properties based on the assumption that all tablet formulations comprise at least one binder, one disintegrant, and one lubricant. Other excipients such as diluents (fillers) or glidants are then added as required. 

It must be stressed that the functions of a glidant and lubricant in a tablet formulation are totally different. A few materials, e.g. talc, can act as both glidant and lubricant, but usually two different excipients are needed. Thus, although colloidal silicon dioxide is an excellent glidant, it has no lubricant activity. Conversely, magnesium stearate, despite its popularity as a lubricant, can hinder rather than promote flow. 

In pharmaceutics, talc is used as a glidant for improved powder flow [7-9] and as a lubricant in tablet formulations [10-13]. Because of its insolubility, it is employed as a filling and dispensing medium [4], Talc is also used extensively in the cosmetic industry in face, body, and foot powders, as well as in aerosol formulations [14]. Cosmetic and pharmaceutical talcs differ only in particle size... 

The performance requirements of a tablet were discussed in the previous section, and it is clear that most tablets will contain several ingredients. The drug substance, probably a filler, a disintegrant and a lubricant will be common to most formulations, while glidants, colourants and wetting agents may also be included. The quality of the final product will be as dependent on the way in which the components are combined as it is on the components selected. Traditionally, tablet formulations have been prepared by one of two methods direct compression or granulation. 

Excipients used for lubrieation in tablet formulations can have an adverse effect on the dissolution eharacteristics of the final tablet. Hydrochlorothiazide tablets lubrieated with talc have been shown to have improved dissolution properties as eompared to similar tablets lubricated with magnesium stearate (Dawoodbhai et al, 1987). This same study also foimd talc to improve hardness, friability and appearance for some systems when compared to other lubrieants. It was additionally noted that different sources of talc showed signifieant variation in their glidant and lubricant efficiencies. 

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]. 

Tablet glidant Agent used in tablet and capsule formulations to improve flow properties of powder mixture Colloidal silica, corn starch, talc...

Commonly used lubricants are listed in Table 5. Talc is traditionally one of the most commonly used glidants, having the additional benefit of being an excellent antiadherent. The level of talc that can be added to a formulation is restricted by its hydrophobic nature, too high levels resulting in decreased wetting of the tablet and a subsequent reduction in the rate of dissolution. Fumed silicon dioxides are... 

For tablets and capsules, excipients are needed both for the facilitation of the tableting and capsule-filling process (e.g., glidants) and for the formulation (e.g., disintegrants). Except for diluents, which may be present in large quantity, the level of excipient use is usually limited to only a few percent and some lubricants will be required at <1%. Details of the types, uses, and mechanisms of action of various excipients for tablet and capsule production have been discussed at length in other articles in this encyclopedia. The types and functions of excipients for tablet production are summarized in Table 1. Although binders. 

Calcium stearate is primarily used in pharmaceutical formulations as a lubricant in tablet and capsule manufacture at concentrations up to 1.0% w/w. Although it has good antiadherent and lubricant properties, calcium stearate has poor glidant properties. 

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