Prevention

Initial dose 15 mg/kg per day, increase by 5 mg/kg per day every 12 weeks to maximum of 35 mg/kg per day, unless marrow depression noted (neutropenia < 2.0 x 10 ⁹ /1, reticulocytes or platelets < 80 x 10 ⁹ /l; Hb < 4.5 g/dl). If this occurs, stop therapy until recovery. Resume at 2.5 mg/kg per day lower). 

Why?

• Patients with more than 3 crises a year who take hydroxyurea have fewer episodes of acute chest syndrome and fewer require blood transfusions. ^a
• Painful crises occur less often (mean of 2 fewer a year) and take longer to occur (mean of 2 months) ^a

Hydroxyurea reduces acute chest syndrome and need for blood transfusion in severe cases

Patient	Treatment	Comparison	Outcome	CER	RRR (95% CI)	NNT (95% CI)
frequent sickle cell crises a	hydroxyurea	placebo	acute chest sydrome at 12 months	35%	53% (25% to 81%)	5 (4 to 12)
			need for blood transfusions at 12 months	50%	36% (14% to 58%)	6 (3 to 15)