Development of bone marrow toxicosis after albendazole administration in a dog and cat. 
Bone marrow toxicosis was detected in a dog and cat following albendazole administration.  Both animals were admitted with pancytopenia.  In the dog, pancytopenia was attributed to severe panmarrow hypoplasia, whereas the cat had hypoplasia of erythroid and megakaryocytic series, but with a left-shifted granulocytic hyperplasia.  Results of cytologic examination of bone marrow from both animals were compatible with acute injury.  Both animals had been treated with albendazole for giardiasis prior to the onset of clinical signs.  Bone marrow toxicosis was attributed to albendazole administration for the following reasons: this was the only or most recent drug administered, other causes of bone marrow toxicosis were not found, and both animals recovered rapidly with supportive care that consisted of fluid and antibiotic administration.  Albendazole induced toxicosis appeared to be dose related in the dog and idiosyncratic in the cat.  On the basis of the findings in this report, there is a potential for the development of albendazole induced bone marrow toxicosis in dogs and cats; therefore, veterinarians should exercise caution when using this drug.