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PRINCIPLES OF TOXICOLOGY

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BIOTRANSFORMATION: A BALANCE BETWEEN BIOACTIVATION AND DETOXIFICATION 61<br />

TABLE 3.1 Pharmacologic Effects with Xenobiotic Metabolism<br />

Phase I Phase II<br />

Amphetamine —P450→ phenylacetone<br />

Active to Inactive<br />

Acetaminophen —UGT/ST→<br />

Cocaine —esterase→ benzoylecgonine Aflatoxin 2,3-epoxide —GST→ 8 glutathionyl-9<br />

hydroxyaflatoxin<br />

Hexobarbital —P450→ Morphine —UGT→ morphine-3-glucuronide<br />

Phenytoin —P450→ Testosterone —ST→<br />

Active to Active<br />

Acetylsalicylic acid —esterase→ salicylic acid<br />

Codeine —P450→ morphine Morphine —UGT→ morphine-6-glucuronide<br />

Heroin —esterase→ morphine Procainamide —AT → N-acetylprocainamide<br />

Primidone-P450→ phenobarbital Thiobarbital —P450→ barbital<br />

Inactive to Active<br />

Chloral hydrate —reductase→ trichloroethanol<br />

Prontosil —reductase→ sulfanilamide<br />

Sulindac —reductase→ sulfide<br />

Inactive to Toxic<br />

Acetaminophen —P450→<br />

N-Hydroxyacetylaminofluorene —ST→<br />

N-acetyl-p-benzoquinine imine<br />

Acetylhydrazine —P450→ acetylcarbonium ion N-Hydroxymethylaminoazobenzene —ST→<br />

Aflatoxin —P450→ aflatoxin-8,9 epoxide Tetrachloroethylene —GST→<br />

Malathion —P450→ malaoxon Tolmetin —UGT→<br />

Nitrofurantoin —reductase→ hydroxylamine<br />

Benzo(a)pyrene 7,8-diol —P450→ benzo(a)pyrene 7,8-diol 9,10-epoxide<br />

Dimethylnitrosamine —P450→<br />

methyldiazohydroxide<br />

Figure 3.4 The balance of reactivity and excretability in xenobiotic metabolism.

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