tokens: All three cytopenias were completely reversible following cessation of treatment ; the time required for recovery of the erythron ( approximately 1 month ) was considerably longer than that of the granulocytes and platelets ( hours to a few days ). Upon rechallenge with either cephalosporin , the hematologic syndrome was reproduced in most dogs tested ; cefonicid ( but not cefazedone )- treated dogs showed a substantially reduced induction period ( 15 +/- 5 days ) compared to that of the first exposure to the drug ( 61 +/- 24 days ). This observation , along with the rapid rate of decline in red cell mass parameters of affected dogs , suggests that a hemolytic component complicated the red cell production problem and that multiple toxicologic mechanisms contributed to the cytopenia .