Effect on bioavailability

Fig. 13 Representation of the sorption of organic compounds to two forms of sediment organic matter, amorphous organic matter and black carbon (BC), and its effect on bioavailability...

Solubility/miscibility Generally very soluble or miscible in water. Soluble in ethanol, com oil, and olive oil. Insoluble in mineral oil Biological considerations Surfactant. May cause micelle formation, with incumbent effects on bioavailability if included at concentrations of 1% or higher. May be associated with irritation if given intravenously or intramuscularly. Dogs have the peculiarity that Tweens injected parenterally induce the spontaneous systemic release of histamine. This response is particularly striking with IV injection, and therefore Tweens should not be used as components of IV vehicles in dogs... 

Uptake occurs from the bioavailable fraction, which in almost all cases corresponds to the dissolved fraction. Sorption and binding to suspended solids, sediments, and DOM have a great effect on bioavailability [71,72] therefore the more hydrophobic surfactants tend to be less bioavailable. Thus, for the same initial concentration, the bioavailable fraction of C12LAS, compared with that of the Cn... 

Drug/Food interactions The time to maximum concentration of zonisamide is delayed in the presence of food, but no effect on bioavailability occurs. 

Calcium-Fortified Orange Juice Effect on Bioavailability... 

Traina, S. J., D. C. McAvoy, and D. J. Versteeg, Association of linear alkylbenzenesulfonates with dissolved humic substances and its effect on bioavailability , Environ. Sci. Technol., 30,1300-1309 (1996). 

Traina, S.J., D.C. McAvoy, and D.J. Versteeg. 1996. Association of linear alkylbenzenesulfonates with dissolved humic substances and its effects on bioavailability. Environ. Sci. Technol. 30,1300-1309. Urano, K., and M. Saito. 1984. Adsorption of surfactants on microbiologies. Chemosphere 13, 285-293. Versteeg, D.J., and S.J. Shorter. 1992. Effect of organic carbon on the uptake and toxicity of quaternary ammonium compounds to the fathead minnow, Pimephales promelas. Environ. Toxicol. Chem. 11, 571-580. 

Air Highly mobile, so pollutants can travel long distances (transboundary issues arise) composition quite stable at given altitude, and so local effect on bioavailability not such an important issue rapid dissolution through mixing can occur pulsed exposure common... 

Rozier, A., Mazuel, C., Grove, J., and Plazonnet, B. (1989), Gelrite(R) A novel, ion-activated, in-situ gelling polymer for ophthalmic vehicles. Effect on bioavailability of timolol, Int. J. Pharm., 57(2), 163-168. 

The effect on bioavailability of changes in the chemical partitioning of Zn in sediments is assessed from correlations of B with ratios of the concentrations of different substrates removed from sediments by different chemical extractants. 

Table 19.6 Most likely food effects on bioavailability for BCS class I—IV drugs.

Some medicines are normally given with food to reduce gastrointestinal side-effects in certain cases coadministration with food increases bioavailability of orally administered preparations. If the labelling states that the pharmaceutical product should be taken with food then a fed study should be used to assess bioequivalence. Fed state studies are also required in bioequivalence studies of modified release formulations. In these cases the objective is to select a meal that will challenge the robustness of the new multisource formulation to prandial effects on bioavailability (see 6.2.4). The test meal selected should take account of local custom and diet and should be consumed within 20 minutes. The product should be administered according to the protocol and within 30 minutes after the meal has been eaten. 

Tagami, K., and Uchida, S. (1998). Aging effect on bioavailability of Mn, Co, Zn and Tc in Japanese agricultural soils under waterlogged conditions. Geoderma 84, 3-13. Tagami, K., and Uchida, S. (1999). Chemical transformation of technetium in soil during... 

The biggest difference between the agents is bioavailability. Bioavailability of bumetanide and torsemide is essentially complete (80% to 100%), whereas furosemide bioavailability exhibits marked intra- and interpatient variability. Furosemide bioavailability ranges from 10% to 100%, with an average of 50%. Thus, if bioequivalent intravenous and oral doses are desired, oral furosemide doses should be approximately double that of the intravenous dose, whereas intravenous and oral doses are the same for torsemide and bumetanide. Coadministration of furosemide and bumetanide with food can decrease bioavailability significantly, whereas food has no effect on bioavailability of torsemide. The intraabdominal congestion that can occur in heart failure also may slow the rate (and thus decrease the peak concentration) of furosemide, which can reduce the diuretic s efficacy. Thus furosemide is most problematic with respect to rate and extent of absorption and the factors that influence it, whereas torsemide has the least variable bioavaUability. 

THERAPY WITH ORAL IRON Orally administered ferrous sulfate is the treatment of choice for iron deficiency. Ferrous salts are absorbed about three times as well as ferric salts, and the discrepancy increases at high dosages. Variations in the particular ferrous salt have relatively little effect on bioavailability. 

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