Lead compound production excretion

Toluene tends to enter brain tissue, which it affects, and accumulates in adipose tissue. Unlike benzene, toluene possesses an aliphatic side chain that can be oxidized enzymatically, leading to products that are readily excreted from the body. The metabolism of toluene is thought to proceed via oxidation of the methyl group and formation of the conjugate compound hippuric acid, as shown in Figure 13.9. 

Some of these oxidative metabolites are biologically active and may even be more toxic than their parent compounds. Conversion by conjugation reactions is considered to lead to termination of the toxicity of these compounds and excretion of the non-toxic conjugates.58 Oxidative metabolism of a parent compound can lead to different products which may be excreted at different rates, as has been demonstrated for hydroxylated benzo[a]pyrenes.58... 

In principle, the excretion of Mc4Pb and Et4Pb and their degradation products can take place by several routes, but on the whole only the urinary excretion has been studied. However, it is expected that R4Pb from the blood can diffuse into the alveoli and be expired. The excretion of organic lead compounds in the feces, sweat, hair, etc. is presumably of limited extent. 

Carbofuran in animals may also be hydrolyzed to produce carbofuran-7-phenol. Hydrolysis of the 3-hydroxyderivative leads to formation of 3-hydrocarbofuran-7-phenol. Other degradation products include /V-hydroxymethyl carbofuran and, as in plants, 3-hydroxy- and 3-ketoderivatives. All of these compounds may become conjugated and excreted by animals in urine and, presumably, bile (Metcalf et al. 1968 Finlayson et al. 1979). At least 10 metabolites of carbofuran are known at present their interrelations are shown in detail by Menzie (1978). 

Another compound of considerable radiopharmaceutical relevance and based on dithiolato donors is the Tc complex of dimercaptosuccinic acid (H2dmsa, (95)). The ligand (95) has both a meso and optically active forms, leading to complexes of different stereochemical configuration, which have very different in vivo behavior. Whereas the complex from racemic (95) leads to a product that is renally excreted without accumulation in any other organ, the complex prepared from... 

Not all agents can be readily metabolized. The toxic metals lead and mercury are elements that cannot be degraded but must still be removed from the body. Another important mechanism of detoxification is the attachment or binding of another compound to a toxic chemical to make it easier for the kidney to filter the compound out of the blood and excrete it in the urine. A primary purpose of the kidney is to screen the blood for waste products and concentrate them in the urine for excretion, as occurs, for example, with mercury. Caffeine is excreted in the urine at approximately the same concentration as the blood because the kidney cannot concentrate caffeine. Vitamins, however, are readily concentrated and excess quickly eliminated in the urine. 

The addition of a phenylsulfoxide moiety to the end of the side chain markedly changes the activity of this class of compounds. This product, sulfinpyrazone (97-11), stimulates uric acid excretion, making it a valuable dmg for dealing with the elevated serum uric acid levels associated with gout. The compound is stiU one of the more important uricosuric agents available today. The starting ester (96-9) is available by alkylation of the dianion from ethyl malonate with 2-chloroethylphenyl thioether. Condensation with diphenylhydrazine (97-3) in the presence of a base then affords the pyrrazolodione (97-10). Oxidation of sulfur with a controlled amount of hydrogen peroxide leads to the sulfoxide and thus sulfinpyrazone (97-11) [107]. 

An alternative process that can lead to the termination or alteration of biologic activity is metabolism. In general, lipophilic xenobiotics are transformed to more polar and hence more readily excreted products. The role that metabolism plays in the inactivation of lipid-soluble drugs can be quite dramatic. For example, lipophilic barbiturates such as thiopental and pentobarbital would have extremely long half-lives if it were not for their metabolic conversion to more water-soluble compounds. 

Certain foreign compounds may cause the retention or excretion of water. Some compounds, such as the drug furosemide, are used therapeutically as diuretics. Other compounds causing diuresis are ethanol, caffeine, and certain mercury compounds such as mersalyl. Diuresis can be the result of a direct effect on the kidney, as with mercury compounds, which inhibit the reabsorption of chloride, whereas other diuretics such as ethanol influence the production of antidiuretic hormone by the pituitary. Changes in electrolyte balance may occur as a result of excessive excretion of an anion or cation. For example, salicylate-induced alkalosis leads to excretion of Na+, and ethylene glycol causes the depletion of calcium, excreted as calcium oxalate. 

Correct answer = E. The patient s pain is caused by gout, resulting from the crystallization of excess uric acid in his joints. The cell death caused by radiation therapy leads to the degradation of nucleic acids from those cells. The degradation of purines from these nucleic acids results in excess production of uric acid—a relatively insoluble compound that can cause kidney stones, as well as gout. The end products of pyrimidine degradation do not cause these problems, because they are all soluble compounds that can be more easily excreted in the urine. 

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