Js. Mccune et al., PRECIPITOUS FALL IN PLATELET COUNT WITH ANAGRELIDE - CASE-REPORT AND CRITIQUE OF DOSING RECOMMENDATIONS, Pharmacotherapy, 17(4), 1997, pp. 822-826
Thrombotic and hemorrhagic events may result from high circulating con
centrations of platelets (> 1,000,000/mm(3)), and measures to reduce t
he platelet count are indicated in symptomatic or extreme thrombocytos
is. The platelet count can be decreased quickly by plasmapheresis, but
the effect is transient. Patients with thrombocytosis secondary to a
myeloproliferative disease, such as chronic myelogenous leukemia (CML)
, frequently require more sustained suppression of the platelet count.
Hydroxyurea, busulfan, and interferon are used to maintain a lower pl
atelet count but are occasionally ineffective or intolerable. An alter
native to these therapies is anagrelide, a quinazolin derivative that
was approved by the Food and Drug Administration in March 1997. Becaus
e current dosing guidelines for anagrelide are scarce, the dosing meth
od of the Anagrelide Study Group that published the largest study to d
ate on the drug's efficacy in thrombocytosis was followed. Two unexpec
ted episodes of anagrelide-induced thrombocytopenia occurred despite f
ollowing these dosing methods. This prompted a critical evaluation of
the pharmacodynamic response and the appropriateness of anagrelide dos
age recommendations. A case of thrombocytosis treated with anagrelide
in a patient with CML is described.