Elimination, -, avoidance

METHOTREXATE ANTIGOUT DRUGS -PROBENECID t methotrexate levels Probenecid 1 elimination of methotrexate renally by interfering with tubular secretion in the proximal tubule and also 1 protein binding of methotrexate (a relatively minor effect). Probenecid competes with methotrexate for renal elimination Avoid co-administration if possible if not possible, 1 dose of methotrexate and monitor FBC closely... 

Maximise your chances in an exam by eliminating avoidable pressure-causing factors that can lead to a poor performance. Try to get a good night s sleep the night before, don t revise into the early hours and plan to arrive early to allow time for possible travel delays. 

Sawhorse projections reveal another reason that anti ehmination is favored. In syn eliminahon, the electrons of the departing hydrogen move to the front side of the carbon bonded to X, whereas in anti elimination, the electrons move to the back side of the carbon bonded to X. We have seen that displacement reactions involve back-side attack because the best overlap of the interacting orbitals is achieved through back-side attack (Section 10.2). Finally, anti elimination avoids the repulsion the electron-rich base experiences when it is on the same side of the molecule as the electron-rich departing halide ion. 

For jet fuels, the elimination of free water using filters and coalescers by purging during storage, and the limit of 5 ppm dissolved water are sufficient to avoid incidents potentially attributable to water contamination formation of micro-crystals of ice at low temperature, increased risk of corrosion, growth of micro-organisms. 

Until now we have been discussing the kinetics of catalyzed reactions. Losses due to volatility and side reactions also raise questions as to the validity of assuming a constant concentration of catalyst. Of course, one way of avoiding this issue is to omit an outside catalyst reactions involving carboxylic acids can be catalyzed by these compounds themselves. Experiments conducted under these conditions are informative in their own right and not merely as means of eliminating errors in the catalyzed case. As noted in connection with the discussion of reaction (5.G), the intermediate is stabilized by coordination with a proton from the catalyst. In the case of autoprotolysis by the carboxylic acid reactant, the rate-determining step is probably the slow reaction of intermediate [1] ... 

Ammonia—water systems operate under moderate pressures and care must be taken to avoid leaks of the irritating and toxic ammonia (qv). Sometimes a third material with a widely different density, eg, hydrogen, is added to the cycle in order to eliminate the need for mechanical pumping. 

Many cellular plastic products are available with different types of protective faces, including composite metal and plastic foils, fiber-reinforced plastic skins, and other coatings. These reduce but do not eliminate the rate of aging. For optimum performance, such membranes must be totally adhered to the foam, and other imperfections such as wrinkles, cuts, holes, and unprotected edges should be avoided because they all contribute to accelerated aging. 

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