Formulation-Related Factors

Free Acid, Free Base, or Salt Form 

Term in modified Noyes-Whitney equation Affected by Comments 

There are several micronization techniques available and they can be broadly classified into mechanical- and solution-based micronization (Table 3) (13). 

Solution-based micronization Crystallization Spray drying Spray freezing 

The choice of polymorph before granulation determines the dissolution rate. Otsuka et al. (26) found that the use of carbamazepine polymorphs I and IV, which are the respective anhydrate and dihydrate forms, gave rise to a higher dissolution rate than polymorphs II and III, which are the anhydride forms, when hydroxypropylcellu-lose solution was employed as binder. This was because the tablets made from polymorphs I and rv were not as hard and thus disintegrated faster upon contact with the 

---

Some well-organized reviews are available for details on these topics,although some formulation-related factors will be referred to in Strategies to Improve Nasal Absorption. ... 

The currendy (ca 1992) marketed injectable and implantable contraceptives are designed to be effective for maximum periods of three months and five years, respectively. There is Htde evidence from programmatic or health reasons that an injectable formulation with a longer effective life span, eg, six months, would not be equally effective. The acceptabiUty and effectiveness of long-acting contraceptives may be determined by the means by which a community deUvers contraceptive products to the pubHc the active life of a product may be determined by economic rather than programmatic or health related factors. 

The generalized relation for the pressure drop for flows through a packed bed was formulated by Ergun (1952). The pressure loss was considered to be caused by simultaneous kinetic and viscous energy losses. In Ergun s formulation, four factors contribute to the pressure drop. They are (1) fluid flow rate, (2) properties of the fluid (such as viscosity and density), (3) closeness (such as porosity) and orientation of packing, and (4) size, shape, and surface of the solid particles. 

Understand the drug-, formulation-, and patient-related factors influencing oral drug bioavailability,... 

Other application related factors, which have an impact on the ink formulation include ... 

The solubility of a drug, and the compatibility of a particular solvent with the site of injection, are inter-related factors governing the suitability of this route of administration, and the pharmaceutical formulation that is employed. 

Dosage form related factors include formulation and manufacturing related variables such as particle size, type, and quantity of excipient used, method of manufacturing, compression pressure, derived properties of the powder, and many other factors. 

A stoichiometric factor is a conversion factor relating molar amounts of two species in a chemical reaction (i.e., a reactant to a product, one reactant to another, etc.). The numbers used in formulating the factor are stoichiometric coefficients. 

Because of the high costs of raw materials and the relatively complex synthesis, the 2-cyanoacryhc esters are moderately expensive materials when considered in bulk quantities. Depending on the quantity and the specific ester or formulation involved, the prices for cyanoacryhc ester adhesives can range from approximately 30/kg to over 1000/kg. For these reasons, as weU as several technical factors related to handling and performance, cyanoacryhc ester adhesives are best suited to small bonding apphcations, very often where single drops or small beads are adequate for bonding. In such cases the cost of the adhesive becomes inconsequential compared to the value of the service it performs, and these adhesives become very economical to use. 

It is obvious that the range of possible formulations based on poly(vinyl chloride) and related copolymers is very wide indeed. For each end-use the requirements must be carefully considered and a formulation devised that will give a compound of adequate properties at the lowest cost. In assessing cost it is not only important to consider the cost of the compound but also comparative processing costs, the possible cost of storing additional materials and many other cost factors. 

In modern practice, inhibitors are rarely used in the form of single compounds — particularly in near-neutral solutions. It is much more usual for formulations made up from two, three or more inhibitors to be employed. Three factors are responsible for this approach. Firstly, because individual inhibitors are effective with only a limited number of metals the protection of multi-metal systems requires the presence of more than one inhibitor. (Toxicity and pollution considerations frequently prevent the use of chromates as universal inhibitors.) Secondly, because of the separate advantages possessed by inhibitors of the anodic and cathodic types it is sometimes of benefit to use a formulation composed of examples from each type. This procedure often results in improved protection above that given by either type alone and makes it possible to use lower inhibitor concentrations. The third factor relates to the use of halide ions to improve the action of organic inhibitors in acid solutions. The halides are not, strictly speaking, acting as inhibitors in this sense, and their function is to assist in the adsorption of the inhibitor on to the metal surface. The second and third of these methods are often referred to as synergised treatments. 

The concept of a characteristic reaction temperature must, therefore, be accepted with considerable reservation and as being of doubtful value since the reactivity of a crystalline material cannot readily be related to other properties of the solid. Such behaviour may at best point towards the possible occurrence of common controlling factors in the reaction, perhaps related to the onset of mobility, e.g. melting of one component or eutectic formation, onset of surface migration or commencement of bulk migration in a barrier phase. These possibilities should be investigated in detail before a mechanism can be formulated for any particular chemical change. 

Br0nsted s correlation was developed some years before Hammett s. Here we present a formulation that shows how both LFERs are related for general acid catalysts. For the sake of simplicity, we ignore the statistical factors of p and q. The Hammett equation applied to the values of bh is... 

In addition to detergency performance and feedstock economics, other factors related to the processing of these powder formulations must be considered, such as sulfonation/sulfation, crutcher slurry preparation, and spray drying. AS and AES are thermally and hydrolytically less stable than LAS. Care must be taken in spray drying to avoid decomposition and pluming problems. This may place a limitation on the levels of AS and AES in spray-dried laundry powders. 

---