Fewer undesirable side effects

Advantages to Membrane Separation This subsertion covers the commercially important membrane applications. AU except electrodialysis are pressure driven. All except pervaporation involve no phase change. All tend to be inherently low-energy consumers in the-oiy if not in practice. They operate by a different mechanism than do other separation methods, so they have a unique profile of strengths and weaknesses. In some cases they provide unusual sharpness of separation, but in most cases they perform a separation at lower cost, provide more valuable products, and do so with fewer undesirable side effects than older separations methods. The membrane interposes a new phase between feed and product. It controls the transfer of mass between feed and product. It is a kinetic, not an equihbrium process. In a separation, a membrane will be selective because it passes some components much more rapidly than others. Many membranes are veiy selective. Membrane separations are often simpler than the alternatives. 

Chlorine dioxide has been used as a water disinfectant, showing fewer undesirable side effects than chlorine [6]. This agent was shown by Vos et al. [1] to be unreactive toward cellulose acetate membranes. The compatibility of chlorine dioxide with other membrane types has not been studied. 

T Aspirin (acetylsalicylate Fig. 21-15b) irreversibly inactivates the cyclooxygenase activity of COX by acetylating a Ser residue and blocking the enzyme s active site, thus inhibiting the synthesis of prostaglandins and thromboxanes. Ibuprofen, a widely used nonsteroidal antiinflammatory drug (NSAID Fig. 21-15c), inhibits the same enzyme. The recent discovery that there are two isozymes of COX has led to the development of more precisely targeted NSAIDs with fewer undesirable side effects (Box 21-2). 

In attempts to discover chugs demonstrating fewer undesirable side effects than morphine, many synthetic analogues have been prepared. Some of these are shown in Table 1. 

Ethers are named using the radical names derived from their parent hydrocarbons. Their names end with the word ether. Diethyl ether was used as an anesthetic until compounds with fewer undesirable side effects were found. It is still widely known as ether, just as ethanol is known as alcohol. Ethers and alcohols can be isomers of each other because both classes have the general molecular formula C H2 +20. 

Fewer undesired side effects Less strength loss by moisture controlled fixation of easy-care finishes... 

Practically all salts of a.spirin. except lho.se of aluminum end calcium, are unstable for pharmaceutical use. The.se salts appear to have fewer undesirable side effects and to induce analgesia faster than aspirin. A tinied-rclca.se preparation of aspirin is available. It docs not appear to offer any advan-uges over aspirin, except for bedtime dosage. 

Amphetamines are drugs that mimic the effects of epinephrine, or adrenalin. Because effects such as mental illness and brain damage can result from overuse of amphetamines, they currently have limited medical use. Metamphetamines are similar to amphetamines in structure and action but have fewer undesirable side effects. Ritalin (methylphemdate), commonly used to treat attention deficit disorder, has essentially the same mode of action as amphetamines. Ritalin abuse by middle and high school students has become a common concern. 

In the twenty-first century, chloroform has been almost entirely replaced as an anesthetic by other compounds that are more effective and have fewer undesirable side effects. The compound is now used almost exclusively for the production of hydrochlorofluorocarhons (HCFCs), compounds developed to replace chlorofluorocarhons (CFCs) that have been banned because of their harmful effects on Earth s ozone layer. 

One year after the introduction of fludrocortisone, the A-corticoids were brought forth into clinical medicine. Investigators at Sobering observed that the 1-dehydro derivatives of cortisone and hydrocortisone—namely, prednisone and prednisolone—are more potent antirheumatic and antiallergenic agents than the parent compounds and produced fewer undesirable side effects. These compounds are known as A -corticoids, because they contain an additional double bond between positions 1 and 2 (Fig. 33.10). 

Although benzodiazepines were originally believed to have fewer harmful side effects than barbiturates, scientists and others who study these drugs now say benzodiazepines actually share many of the same undesirable side effects of barbiturates and are every bit as dangerous in certain circumstances. 

A gastric function test based on the ability of histamine to stimulate the parietal cells of the stomach to produce hydrochloric acid. However histamine may have undesirable side effects and so Histalog, a synthetic analogue of histamine, may be used instead as this has fewer side effects. 

The most comprehensive examination of the Rokita kinetic procedure from a synthetic standpoint was carried out by Barrero and coworkers.6 They examined the effects of various leaving groups, solvents, nucleophiles, and their equivalents on subsequent [4 + 2] cycloadditions. Avast excess of the intended nucleophile (50-100 equiv) must be employed, because the fluoride triggered (3-elimination proves nearly instantaneous at room temperature resulting in a high concentration of a species that is prone to undergo dimerization and other undesired side reactions that are irreversible at these low temperatures (Fig. 4.7). Use of fewer equivalents of the intended nucleophile led to a rapid drop off in yield. For example, 5-10 equivalents of ethoxy vinyl ether (EVE) affords only a 5-10% yield of the desired benzopyran... 

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