• Assess for signs of infection (fever, sore throat, cough, hoarseness, pain in lower back or side, difficult or painful urination). If these symptoms occur, notify health care professional immediately.
• Anemia may occur. Monitor for increased fatigue, dyspnea, and orthostatic hypotension.
• Assess for bleeding (bleeding gums, bruising, petechiae, guaiac stools, urine, and emesis). Avoid IM injections and taking rectal temperatures. Hold pressure on all venipuncture sites for at least 10 min.
• Monitor intake and output, appetite, and nutritional intake. Adjust diet as tolerated to maintain nutritional status.
• Monitor for signs and symptoms of cutaneous vasculitis (vasculitic ulcerations, gangrene) during therapy. If signs occur treat vasculitis and discontinue hydroxyurea.
• Monitor for signs and symptoms of pulmonary toxicity (pyrexia, cough, dyspnea, or other respiratory symptoms) frequently, investigate and treat promptly. Discontinue hydroxyurea and manage with corticosteroids.

Lab Test Considerations:

• Verify negative pregnancy status of women with reproductive potential before starting therapy.
  • Monitor CBC and differential in patients with malignancy prior to and at least weekly during therapy. The onset of leukopenia occurs within 10 days of beginning therapy. Recovery usually occurs within 30 days. Notify health care provider if WBC <2500 mm³ or if a precipitous drop occurs. Institute thrombocytopenia precautions if platelet count <100,000/mm³. May cause temporary increase in mean corpuscular volume (MCV).
  • Monitor CBC with differential and platelets in patientswith sickle cell disease every 2 wks. Dose increase may be given until mild myelosuppression (absolute neutrophil count 2,000 cells/mm³ to 4,000 cells/mm³) is achieved, up to a maximum of 35 mg/kg/day. Hydroxyurea should be held if neutrophils <2000 cells/mm³, platelet count <80,000 cells/mm³, hemoglobin level <4.5 g/dL, or reticulocytes <80,000 cells/mm³ when hemoglobin <9 g/dL. After hematologic recovery, reduce dose by 5 mg/kg/day from dose causing toxicity, may titrate up or down 5 mg/kg/day every 8 wks after patient stable with no hematologic toxicity for 24 wks. If hematologic toxicity occurs twice, permanently discontinue hydroxyurea.
  • Monitor renal (BUN, serum creatinine, and uric acid) and liver function tests (AST, ALT, bilirubin, and LDH) prior to and periodically during therapy. May cause ↑ BUN, serum creatinine, and uric acid concentrations.
  • Monitor fetal hemoglobin (HbF) to determine efficacy. Obtain HbF levels every 3–4 months. Monitor for an increase in HbF of at least twofold over baseline value.
  • May cause false elevations in serum uric acid, urea, or lactic acid concentrations.
  • May cause false elevations in sensor glucose results from certain continuous glucose-monitoring systems and could lead to hypoglycemia if sensor glucose results are used to dose insulin.

Toxicity and Overdose:

• CBC results in an acceptable range for sickle cell diseaseinclude neutrophils ≥2500 cells/mm³, platelets ≥95,000 cells/mm³, hemoglobin >5.3 g/dL and reticulocytes ≥95,000 cells/mm³if hemoglobin concentration <9 g/dL. Levels are toxic if neutrophils <2000 cells/mm³, platelets <80,000 cells/mm³, hemoglobin <4.5 g/dL and reticulocytes <80,000 cells/mm³if the hemoglobin concentration <9 g/dL.