Comparison of starting doses of anagrelide as a first-line therapy in patients with cytoreductive therapy-naive essential thrombocythemia: difference between starting at 0.5 and 1.0 mg/day.

Anagrelide is widely used for cytoreductive therapy in patients with essential thrombocythemia who are at high risk for thrombosis. The recommended starting dose in the package insert of anagrelide varies by country. A high starting dose leads to an early onset of action, but causes a higher incidence of adverse events. This relationship indicates that both the onset of action and side effects of anagrelide are dose dependent. We retrospectively compared the efficacy and safety of anagrelide as a first-line drug between patients with essential thrombocythemia who started at 0.5 or 1.0 mg/day. Incidence of total adverse events and anagrelide-related palpitation, discontinuation rates, and the median daily dose of anagrelide were lower in the 0.5 mg/day group than in the 1.0 mg/day group; however, comparable platelet-lowering effects were achieved in both groups. These data suggest that a low starting dose of anagrelide followed by dose escalation may result in fewer adverse events and lower discontinuation rates, while providing desirable platelet-lowering effects. Initiating anagrelide at a lower dose may be a useful approach in actual clinical practice.