A 45 year old female patient presents with symptoms of easy bruisability and frequent headaches. Physical examination show a moderate splenomegaly. Blood counts shows a normal leucocyte count and a platelet count of 1000 x 103/cu mm. The leucocyte alkaline phosphatase score is normal. Which one of the following is the drug of choice for the treatment of this patient?
Hydroxyurea Radioactive phosphorus Anagrelide None