Choice of Formulation

We consider each of three different choices of formulation and the subsequent effect that these have on discretization of the problem. 

Under all but laminar flow conditions, the steady-state pipeline network problems are described by mixed sets of linear and nonlinear equations regardless of the choice of formulations. Since these equations cannot be solved directly, an iterative procedure is usually employed. For ease of reference let us represent the steady-state equations as... 

The chemical incorporated in a vehicle should reach the surface of the skin at a suitable rate and concentration. If the site of action lies in the deeper layers of the epidermis or below, the substance must cross the stratum comeum, if the skin is intact. Both processes, diffusion from the dosage form and diffusion through the skin barriers, are inextricably linked. They should be considered simultaneously and can be influenced by the choice of formulation. 

E Role in therapy Antihemophilic factor is indicated for the treatment of bleeding episodes or perioperative treatment in patients with hemophilia A. Prophylactic use has also been advocated for the prevention and/or reduction of bleeding episodes. The largest issue in treatment with antihemophilic factor is the choice of formulations because of the relative risk of viral transmission. Recombinant factor VIII has the lowest risk of transmission of blood-borne viruses, but its use may be limited due to cost and availability. 

The following factors (which depend on the nature of the emulsifying agent and/or on a suitable choice of formulation and manufacturing conditions) favour emulsion stability ... 

On entering the stomach an oral dose must first dissolve in the aqueous environment, prior to being absorbed across the walls of the gastrointestinal tract. The rate and extent of dissolution is therefore an important parameter. Solubility issues are discussed elsewhere in this book (see Chapter 4), but it is important to note that any new drug must possess the correct balance between aqueous solubility, allowing it to dissolve in the stomach and lipophilicity, to permit transfer across biological membranes. Poor solubility can result in a low oral bioavailability, although this problem may be resolved in some instances by judicious choice of formulation. 

The factors which Influence the choice of formulation are pesticide physical properties (melting point, solubility, volatility), pesticide chemical properties (hydrolytic stability, thermal stability), soil application vs. foliar application, crop and cultural practice, pesticide biological properties (crop selectivity, transport), and economics. 

Many oral solutions are intended for pediatric administration, of which oral solution formulations are a subset of a larger choice of formulation type such as suspension, syrup, powder or microcapsules for constitution to a suspension, powder for reconstitution to a solution or suspension, solid particles (powder, coated particles, extended release, enteric-coated granules, beads) in packets or capsules to be sprinkled on food, oral powders, and chewable tablets. The broader topic of pediatric formulation development is beyond the scope of this chapter, but this chapter will cover selected oral solutions for pediatric administration. 

Beyond considering the solvent formulators must also consider the biology and state of the skin, and whether transient or sustained delivery is desired. Generally, semisolid formulations are selected for increased residence on the skin, and liquid formulations for a rapid short-term input of permeant into the skin. In both the clinical and cosmetic domains, skin type can affect the choice of formulation base in that usually for normal to oily skin types, gels are preferred but for normal to dry skin types lotions are usually selected and for dry skin, creams are often the preferred base. As well as skin type, the skin site to be treated can affect vehicle selection. For example, for hairy areas lotions, gels or sprays are usually preferable as these spread better whereas for intertriginous areas, creams or lotions are usually employed. 

Both forms of the transport equation have been used describing the evolution of the interface. The choice of formulation seems to be a matter of convenience. 

The minimisation of crop damage by the judicious choice of formulation type. 

Polyether acrylates are not a common choice of formulations for EB curable coatings. These oligomers have low to very low viscosity and often exhibit very high flexibility. Interestingly, because of the polyether backbones, they are compatible with water and can be used for water thinable formulation. 

Many potential degradation products are not observed in protein pharmaceuticals, primarily because much care is taken in the choice of formulations, lyophilization, and storage conditions in order to maintain protein stability. Thus, degradation is minimized and usable shelf lives are on the order of years. In order to study the degradation pathways of a biopharmaceutical protein, and to evaluate the stability-indicating ability of the analytical methods, it is sometimes necessary to perform forced degradation studies, where the biopharmaceutical protein is subjected to a variety of stress conditions, such as varying pH, elevated temperature, or the addition of oxidants. 

A careful choice of formulation and chemistry is needed in this process. It is also possible to increase the amount of UV energy by increasing the number and power of the lamps used. The amount of UV energy used can be regulated based on the condition... 

The same general principles determine xylem translocation of herbicides whether they are foliage applied or soil applied. Provided that the barrier of cuticular penetration can be largely overcome by appropriate choice of formulation, application to foliage is a more reliable way of getting herbicides into the plant. This route avoids the losses caused by sorption to soil, and it bypasses the endodermal barrier surrounding the vascular tissues in the root. Once through the cuticle and into the leaf tissue. 

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