Pharmaceutical systems types

Because of the nature of modern pharmaceutical systems, formulators have made more complete investigations of the materials they use. This interest has identified several materials that may have more than one use in tableted systems. The type of effect that an excipient will produce is often dependent upon the concentration in which it is used. For example, Table 5 lists some multiuse excipients and the corresponding concentration ranges required for their various applications. 

There are two general types of optimization problem constrained and unconstrained. Constraints are restrictions placed on the system by physical limitations or perhaps by simple practicality (e.g., economic considerations). In unconstrained optimization problems there are no restrictions. For a given pharmaceutical system one might wish to make the hardest tablet possible. The constrained problem, on the other hand, would be stated make the hardest tablet possible, but it must disintegrate in less than 15 minutes. 

As can be seen in Fig. 3b, it is important to specify whether data are represented as a number distribution (obtained by a counting technique such as microscopy) or as a weight distribution (obtained by methods such as sieving), since the results will not be the same. Hatch and Choate [4] have developed equations for converting one type of diameter to another the relationships between them are summarized in Table 2. Note that caution should be exercised in using the Hatch-Choate conversions if the distributions do not closely fit the log-normal model. While this distribution is the most frequently used to describe pharmaceutical systems, other distribution functions have also been developed [2,5,6],... 

A second type of solid phase is also possible, and commonly found in pharmaceutical systems. In this case, molecules in the solid phase are randomly distributed like those of the liquid phase, and do not posses long range order. A solid of this type is called amorphous or glassy, and is often found in organic molecules that have several flexible bonds. 

There seems to be no limit to the types of pharmaceutical systems that can be isolated in the amorphous state. In the literature, samples of sugars, acids, bases, polymers, buffers, inorganics, salts, natural products, proteins, and low-molecular-weight APIs have all been reported to exist in an amorphous form. Likewise, pharmaceutical raw materials, intermediates, and final products that include these amorphous materials are widespread and varied (Table 1). 

Adsorption may be defined as the process of enrichment of one or more substances at a surface or as the taking up of one substance at the surface of another.P It can occur at any type of interface. However, in the context of pharmaceutical systems the interfaces where surfactant adsorption is important are the gas-liquid, liquid-liquid, gas-solid, and liquid-solid interfaces. 

Vehicles that exhibit the unusual property of Bingham-type plastic rheological flow are characterized by the need to overcome a finite yield stress before flow is initiated. Permanent suspension of most pharmaceutical systems requires yield-stress values of at least 2-5 Pa (20-50 dyn/cm ). Bingham plastic flow is rarely produced by pharmaceutical gums and hydrophilic colloids. National Formulary (NF) carbomers exhibit a sufficiently high yield value at low solution concentration and low viscosity to produce permanent suspensions. The carbomers, however, require a pH value between 6 and 8 for maximum suspension performance. The polymer is essentially incompatible... 

Shimoyama and coworkers " reported a NIR analysis of photodegradation of poly(methyl methacrylate) using an in situ fiber optic device. This type of technology from a related discipline is notable as a potential application for pharmaceutical systems. 

Emulsions are heterogeneous dispersions of immiscible liquids pharmaceutically both types, oil in water (o/w) and water in oil (w/o), are of interest. Mechanical work is required to break up the liquid to be dispersed to small droplets. Thermodynamically emulsions are unstable systems, because the interfacial tension between the two liquids causes droplets of the disperse phase to coalesce, approaching the state of complete phase separation. To counteract this tendency an emulsifying agent must be added that occupies the interfaces between dispersed droplets and bulk liquid thereby lowering the interfacial tension. 

SMB technology is now a mature technology adopted by pharmaceutical industry. The existence of an organized body of knowledge [39, 40] was helpful in optimizing SMB systems and making them acceptable by the industry. The future will require dynamic simulation for systems with small number of columns, e.g., configurations of the type 1-2-2-1 as encountered in some cases and also in view of process control to improve process performance. 

Documentation is at the core of all quality systems, and was discussed in Chapter 2. Examples of the types of documentation associated with pharmaceutical production are shown in Figure 11.9. European regulations require that records which permit tracing of the full history for each batch of product should be retained for 1 year after expiry of the product or 5 years, whichever is the longer. US regulations require the retention of records for 1 year after batch expiry or 3 years after the last distribution in cases of some OTC products where no expiry date is assigned. Additionally, the US regulations require the preparation of a Master Production and Control Record ,... 

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