Preliminary studies of offspring exposure to phenylbutazone and ivermectin during the perinatal period in a Holstein cow-calf model.

The pregnant Holstein cow and her newborn calf were evaluated as an animal model to study in utero and for lactational drug transfer and offspring exposure. A nonsteroidal antiinflammatory drug, phenylbutazone, and an antiparasitic drug, ivermectin, were tested in the model. Prior to parturition, pregnant cows were dosed orally to steady state with phenylbutazone at 4 g/day or given a single subcutaneous injection of 200 microg ivermectin/kg body wt.