Use of danazol for treatment of corticosteroid-resistant immune-mediated thrombocytopenia in a dog.

A routine health screen of a 7 1/2-year-old female Beagle participating as a control in a long-term study revealed thrombocytopenia. Immune thrombocytopenia was diagnosed on the basis of regenerative bone marrow findings (high number of megakaryocytes) and evidence of antiplatelet antibodies. Treatment with prednisone at dosages up to 1 mg/kg of body weight every 12 hours resulted in limited improvement, with relapses of severe thrombocytopenia thwarting attempts to taper the corticosteroid, and was further complicated by side effects of the drug. Addition of danazol to the treatment regimen (5 mg/kg, q 12 h) resulted in remission of the thrombocytopenia within 2 weeks and permitted the dosage of prednisone to gradually be reduced and discontinued. Associated with this response was a decrease in platelet-associated IgG to values comparable with control samples.