Tofimilast is a potent phosphodiesterase-4 (PDE4) inhibitor with low oral bioavailability and no emesis-associated behaviors in ferrets at plasma concentrations up to 152 ng/ml. Tofimilast exhibited an apparent slower absorption through the rat lung after administration as a dry powder, although absorption half-life values were <1 h and therefore the significance of a formulation effect for this compound is questionable. Tofimilast was tested as a therapeutic agent against asthma and chronic obstructive pulmonary disease but development has been discontinued due to lack of efficacy.