Factors affecting absorption

The interaction between drugs in the lumen and intestinal components is generally a poorly studied area, and it is difficult based on in vivo data to discriminate such effects from other factors affecting absorption. In addition, evidence for the in vivo relevance of available in vitro methods is sparse. 

Factors affecting absorption, distribution, binding, metabolism, and elimination of chemicals... 

Problem 12.12 How do the following factors affect absorption frequencies Use data in Tables 12-1 and 12-2. (a) For C—H stretch, the hybrid orbitals used by C. b) Bond strength i.e., change in bond multiplicity, (c) Change in mass of one of the bonded atoms e.g., O—H versus O—D. (d) Stretching versus bending, (e) H-bonding of OH. <... 

Physiological factors affecting absorption, for example, gastrointestinal (Gl) transit time, gastric emptying time, Gl content, surface area, pH, enzymatic metabolism, and site-speciLc absorption... 

Factors Affecting Absorption from Subcutaneous Sites... 

Strub K M, Aeppli L, Muller R K 1982 Pharmacological properties of carprofen. European Journal of Rheumatology and Inflammation 5 478-487 Sullivan M, Snow D H 1982 Factors affecting absorption of non-steroidal anti-inflammatory agents in the horse. Veterinary Record 110 554-558 Sunshine A, Olson N Z, Zighelboim I et al 1993 Ketoprofen, acetaminophen plus oxycodone and acetaminophen In the relief of postoperative pain. Clinical Pharmacology and Therapeutics 54 546-555... 

Thus, the nature of these membranes and the chemical and physical properties of the toxicant in question are important factors affecting uptake. The mechanisms by which chemical agents pass through the membranes include (1) filtration through spaces or pores in membranes (2) passive diffusion through the spaces or pores, or by dissolving in the lipid material of the membrane and (3) facilitated transport, whereby specialized transport systems carry water-soluble substances across the membrane by a lipid soluble "carrier" molecule, which complexes with the chemical. It can be seen then that, as far as the chemical properties are concerned, lipophilicity is the most important factor affecting absorption. 

What is the most important chemical property factor affecting absorption of a pollutant ... 

All the factors affecting absorption as presented in Figure 13.1 should be addressed. Salient data need to be collected and patients monitored. Patients may need to be stratified for various factors such as concomitant medications, sex, and age. 

Factors affecting absorption from the oral mucosal membranes include lipid solubility and molecular weight of the drug, pH of the saliva and the rate of removal by the blood as well as the application of the correct technique. 

Table 2.1 Factors affecting absorption from the gastrointestinal tract...

A technique closely related to flame emission spectrometry is atomic absorption spectrophotometry (AAS) because they each use a flame as the atomizer. We discuss here the factors affecting absorption and because of the close relationship of atomic absorption and flame photometry, we shall make comparisons between the two techniques where appropriate. 

Garland T, Cataldo D, McFadden K. et al. 1987. Factors affecting absorption, transport, and form of plutonium in plants. In Pinder J, et al., eds. Environmental research on actinide elements. Office of Science and Technical Information. U.S. Department of Energy, Springfield, VA. NTIS no. 

Additional difficulties arise when making dose-response assessments. First, one must select what measure of dose to use. A common measure is milligrams of chemical per kilogram of body weight per day. Then there is appUcation of a scaling factor between species. Procedures make an adjustment for absorption rates, because several factors affect absorption. Also, there is an extrapolation from high to low doses. Not all extrapolations are linear or linear over a range of dose rates. There may be a need also to make an adjustment for threshold effects. For some substances, there are no-observable-effect levels (NOELs) or lowest-observed-effect levels (LOELs). 

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