Absorption physicochemical factors affecting

The physicochemical factors affecting the absorption are lipid solubility, dissolution rate, salt from complexation, viscosity and drug stability in the GIT. 

Factors affecting drug absorption physicochemical factors... 

Kerberle, H. (1971). Physicochemical factors of drugs affecting absorption, distribution and excretion. Acta Pharmacol. Toxicol. 29 (Suppl 3) 30-47. 

Stevens, P.J.G., Baker. E.A., and Anderson. N.H. Factors affecting the foliar absorption and redistribution of pesticides. 2. Physicochemical properties of the active ingredient and the role of surfactant, Pestic. Sci., 24(l) 31-53,1988. 

Factors affecting the delivery include the physical form of the drug, the entry into the body, the design and the formula of the product. This may depend on the physicochemical properties of the excipients, the control of the drug-excipient interaction at the absorption site. Thus, polysaccharides may play an essential role for effectiveness and reliability of the different drug delivery systems. 

Welling, P.G. Physicochemical and formulation factors affecting drug absorption. In Pharmacokinetics Processes, Mathematics, and Applications, 2nd Ed. American Chemical Society Washington, DC, 1997 88. 

Despite the fact that a plethora of dietary factors could, and will, affect the absorption characteristics of phytochemicals, this area has not been systematically explored. One reason might be the complexity of dietary factors and their interactions that could affect absorption. A nonexhaustive list would include the volume and composition of the food consumed, pH, caloric density, viscosity, nutrients (carbohydrates, protein, fat, fibers), alcohol, caffeine, and the presence of other phytochemicals. Such dietary factors affect the functional status, motility, and acidity of the gastrointestinal tract in a complex manner and modify the physicochemical properties, formulation, and dissolution characteristics of the compound of interest. Calcium in dairy products, for example, has the potential to chelate tetracyclines and fluoroquinolones and, thereby, reduce their bioavailability and biological activity [31]. 

Nelson E and Levy G. Physicochemical and physiologic factors affecting die absorption of warfarin in man. 

This paper begins with a review of the behaviour of inhaled actinide aerosols, the affect of physicochemical factors, the bio kinetic model for limg dissolution and absorption and dissolution tests. The paper then presents a technique for doing new solubility measurements adapted from successful published methodologies. The results achieved using a pilot solubility test are then discussed along with proposals for further work. 

Orally administered dosage forms are absorbed into the systemic circulation following dissolution in the GI tract. Because substances must be in solution for the absorption from the GI lumen, the absorption rate of poorly water-soluble drugs is limited by their rate of dissolution. The dissolution rate is affected by the unique physicochemical properties of the drug and by physiological factors the pH, composition, and hydrodynamics of the GI medium. 

Absorption, in general, is treated as a physicochemical transport process based on computations of logP (the octanol/water partition coefficient) and solubility governed by factors such as polar surface area on the molecule. It is conceivable that SNPs in drug transporter genes will affect the pharmacokinetic properties of compounds and, therefore, these may have to be taken into consideration in the design process. 

Absorption describes the rate and extent to which a drug leaves its site of administration and enters the general circulation. Factors that, therefore, affect absorption include the physicochemical properties of the drug that determine transfer across cell membranes as described earlier formulation or physical state of the drug site of absorption concentration of drug circulation at absorption site and area of absorbing surface. 

Absorption from the Gl tract is governed by many factors. Broadly, it can be categorized into three classes physicochemical properties, biopharmaceutical factors, and physiological and pathophysiological factors (Mojaverian et al., 1985,1988 Nomeiretal., 1996). Since this chapter focuses on the pharmacokinetic perspectives, the main factors that could affect drug absorption are merely listed below, and will be discussed in detail in other chapters. 

The physicochemical properties of a molecule which affect its absorption across the nasal epithelium are broadly the same as those affecting transepithelial absorption at any site and have been discussed extensively in Section 1.3.4. These factors influence the mechanism and rate of drug absorption through the nasal epithelium. 

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