Table 2 Biopolymers in Modified Drug Delivery/Release
Nonbiodegradable
Biodegradable
Soluble
Hydrogels
Silicones
Polyactic/glycolic acid
Cellulose derivatives
p-HEMA
Polyethylene-vinyl acetate
Poly/acetones
Polyacrylic esters and polymethacrylic esters
PVA
Poly (D-(-)-3-hydroxy butyric acid)
PEO
Polyurethanes
PVP
Others
Poly (ortho esters)
Others
Others
PVC
Polyanhydrides
Carbopol resins
Dextrans
Polyamides
of the active ingredient necessary to achieve the desired effect and the amount of excipient present should be considered:
the effect of the active ingredient is not influenced by the quantity of the excipient that is necessary for the preparation of the drug product;
the effect of the active ingredient is increased in the presence of an increased amount of the excipient; a smaller quantity of the active ingredient is thus necessary to achieve the same effect;
the effect of the active ingredient is decreased by increasing the quantity of the excipient; and
the effect of the active ingredient is inhibited by the excipient only to a certain degree.
Table 3 lists the advantages and disadvantages offered by various excipients used in direct compression and wet granulation. Tables 4 and 5 document the characteristics of lactose diluents and the tableting properties of various cellulose excipients, respectively.
B. Performance Characteristics
During the past few years, tremendous interest has sprung up regarding the nature of excipient materials administered with an active drug. Excipients are typically chosen for inclusion in a formulation for specific formulation and are often classified by their intended mode of action. They can exert profound influences on the stability of the finished product, its bioavailability profile, and the ease with which the product can be manufactured. As a result, the performance characteristics of the excipients need to be assessed and established. They primarily pertain to
