Excipients frequently used

Skrabanja et al. [3.6.] do not accept a combination of 12 different excipients e. g. for erythropoetin as the efficacy of each component cannot be proven. The mostly frequently used excipients are listed in five groups ... 

Excipients bring properties to formulations that facilitate the conversion of the API to a medicine. These functional properties will depend on the particular formulation. For parenteral products, open wound treatments, and ocular treatments, there are specific additional requirements concerning impurities, microbiological load, and endotoxins. However, excipients intended for nonsterile applications very often function, because they are not single chemical compounds. There are other functional or concomitant components frequently present, which are necessary to achieve the required performance (functionality) of the excipient in use. These should be considered separately from any impurities, process residues, or foreign substances that may be present. (In some applications, certain components that have traditionally been considered to be impurities or residues, may actually be concomitant components.) It is important to understand that these other components, whatever their source, may also interact with the API or other excipients. 

Mannitol, a frequently used excipient, shows complexity in its application. Yu et al. [1.148] reported the formation of a metastable mannitol hydrate during freeze-drying. The amount of mannitol hydrate varies from vial to vial in one batch. It reduces the... 

Excipients. Most tablets and capsules are complex mixtures containing a small amount of one or more drugs together with a larger amount of excipients. The following substances are frequently used as sxcipients. 

The study of stability is not restricted to looking at degradation of the active . It is prudent to bear in mind that any degradation of a formulation excipient may lead to a change in the drug release characteristics of the formulation. For example lactose, a frequently used excipient, can undergo anomerisation in solution between its a- and p- forms. It is conceivable that this could take place in the solid state in a formulation stored under extreme conditions. This could be studied by LC (Figure 12.13). 

Because of the interactions existing between different materials as well as between like materials, the performance of excipients in a formulation could be different from the performance of the excipients themselves. The most frequently used procedures in pharmaceutical processing for solid dosage formulations are mixing, granulation, and compaction, as well as storage of finished dosage forms. The effects of adsorption on these procedures have been studied, observed, and utilized widely in the pharmaceutical industry. 

In solid dosage forms, granulation is frequently used to improve excipient properties such as flowability, compactibility, bulk density, granule strength, dissolution rates, and so The granulation process... 

Solid formulations for sustained drug release may contain mesogenic polymers as excipients. The mesogenic polymers form a matrix, which is usually compressed into tablets. Some of the most frequently used excipients for sustained release matrices include cellulose derivatives, which behave like lyotropic liquid crystals when they are gradually dissolved in aqueous media. Cellulose derivatives such as hydroxy-propyl cellulose or hydroxy-propylmethyl cellulose form gel-like lyotropic mesophases in contact with water, through which diffusion takes place relatively slowly. Increasing dilution of the mesophase with water transforms the mesophase to a highly viscous slime and then to a colloidal polymer solution. 

TG is frequently used for analysing the composition of adhesives by quantifying the amount of moisture which is present and the amount of volatiles associated with a reaction. Fast heating rate TG allows detection of very low levels of volatiles in small samples. TG is also used for the quantitative determination of solvents in polymeric additives used as pour-point depressants and flow improvers [220], PET moisture analysis by means of TG can be carried out at ppm level [221]. Thermogravimetry (eventually combined with GC or IR and subambient DSC) is very useful for the determination of residual solvents or for the study of interactions of water with polymers (important for modified release formulations for which swelling or gel formation of polymeric excipients is relevant). TGA has also been employed to measure the continuous desorption of sorbed SCCO2 in polymeric materials [222]. 

There are a wide range of excipients which can be used in forming matrix systems, and among them, polymers constitute the largest group. The following are the most frequently used in inert and hydrophilic matrices (Table 4.1). 

A variety of polymers are employed as hydrophilic matrix-forming excipients whose characteristics may play a key role and significantly influence the behavior of these devices. Cellulose ethers, especially hydroxypropyl methylcellulose (HPMC), are frequently used as the basis for preparing hydrophilic matrix tablets. 

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