As a class, antimetabolites exhibit S-phase specific cytotoxicity. These agents chemically resemble the purine and pyrimidine nucleoside bases involved in normal cellular DNA replication (adenine, guanine, cytosine, and thymine) or impair enzymes involved in protein or DNA synthesis. These nucleoside analogs essentially "trick" cells into incorporating the toxic drug into newly synthesized DNA strands in place of normal nucleotide bases.5 20 This leads to synthesis inhibition and chain termination. Multiple antimetabo-lites are currently in use (Table 101.2).

Table 101.;

Antimetabolite compounds and selected toxicities

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