Phase I trial of cytarabine and hydroxyurea.

A combination of hydroxyurea (HU) and cytarabine (ara-C) can overcome ara-C resistance in vitro. To determine the pattern of toxicity of this combination, 22 patients with refractory leukemia and lymphoma were treated for 5 days with ara-C (100 mg/m2/day by constant infusion) and escalating doses of HU (0.375-1.77 g/m2 every 6 hours). Hematologic toxicity was severe even at the lowest HU dose level. Skin and mucosal toxic effects were frequent but not dose-limiting. No novel types of toxic effects were observed.