Haematological changes in two Lagenorhynchus obscurus treated with Ketoconazole

Two Cape dusky dolphins, Lagenorhynchus obscurus (Gray, 1828), (one male and one female) residing in the same holding pool and both showing signs of candidiasis, were treated with Ketoconazole. This resulted in clinical improvement of both animals and an improved blood picture in the male. However, full blood counts from the female revealed severe pancytopenia on day 37 of treatment. On withdrawal of the drug and after a period of supportive therapy, the haemoglobin level, platelet count and white cell counts (WCC) normalized. As there was no definite relationship between drug therapy and the blood dyscrasia, it was decided to again treat the female with Ketoconazole on recurrence of severe candidiasis. The drug was administered at a much lower dosage (2.6 mg/kg/day) and the blood picture was monitored regularly. There was improvement in the clinical symptoms and an elevation of the peripheral blood leucocyte count. The dose of Ketoconazole was increased to 5.2 mg/kg/day, but within 7 days, at this higher dosage, blood results revealed neutropenia and mild thrombocytopenia. Administration of the drug was immediately discontinued. Recovery of the peripheral blood parameters occurred over the following three months. Ketoconazole has not been known to cause severe pancytopenia in humans and other species. The authors stress the importance of regular haematological monitoring of cetaceans on long term Ketoconazole therapy. The effect appears to be idiosyncratic rather than dose-related and early recovery occurs if the drug is discontinued before severe cytopenias develop. (DBO)