B. PYRIMIDINE ANALOGUES : 5-FLUOROURACIL, CAPECITABINE
Toxicity
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5-FU has a low therapeutic index (even for an antineoplastic drug)
- primary toxic effects are on bone marrow (danger of spontaneous hemorrhage or life-threatening infection) and GI epithelium
- myelosuppression reaches maximum in 9-14 days
- acute cerebellar syndrome (somnolence, ataxia of trunk or extremities, unsteady gait, slurred speech, nystagmus)
- occurs within weeks/months of initiating treatment in 5% of patients
- complete recovery following cessation of treatment
- alopecia, dermatitis
- hand-foot syndrome (palmar-plantar erythrodysesthesia)