Anagrelide treatment in myeloproliferative disorders.

Platelet-lowering therapy in myeloproliferative disorders includes cytostatic drugs, mainly hydroxyurea, interferon alpha, and anagrelide. Anagrelide is the latest addition to the therapeutic arsenal, and the basis for its use is reviewed. The platelet-lowering efficacy is 70 to 80% in essential thrombocythemia, and the response is rapid; most of the patients reach the treatment goal within a few weeks. Side effects are common, mainly caused by the vascular effects, and include palpitation, headache, loose stools/diarrhea, and edema. Some side effects are time-limited, but late dropout from therapy is not uncommon. The total dropout rate in prospective studies is 30 to 50%. Pharmacologic treatment of side effects is often helpful. Cardiac insufficiency may be worsened in patients with previous heart failure, and special caution is warranted in such patients. Anagrelide has recently been registered in Europe as a second-line therapy in ET but is often used as first-line therapy in the United States, especially in younger patients, due to the concern about increased leukemia risk with cytostatic treatment. The first randomized anagrelide study, with its limitations, gives support for the second-line registration. Given that dose escalation is a problem in some patients with all therapeutic agents used, combination of two drugs in lower doses is a practical option already used by many clinicians without basis in any published study.