The autoradiographic studies on the distribution of 14C-labeled pivaloyloxymethyl (+)-(6R,7R)- 7-[(Z)-2-(2-amino-4-thiazolyl)-2-methoxyiminoacetamido]- 3-[(5-methyl-2H-tetrazol-2-yl)methyl]-8-o xo-5-thia- 1-azabicyclo [4.2.0]oct-2-ene-2-carboxylate (14C-T-2588) in mice

The distribution of T-2588 was studied with whole body autoradiography in normal male mice and pregnant mice using two radioactive T-2588 labeled at the aminothiazole or pivaloyloxymethyl moieties. When (aminothiazole-2-14C) T-2588 was orally administered, the radioactivity was distributed widely to whole tissues except central nervous systems such as brain and spinal cord. In pregnant mice, no detectable radioactivity was present in the fetus. These results suggested that T-2588 was well absorbed and hardly crossed the blood-brain barrier and placenta. At 4 hours after administration, radioactivity was only observed in gastrointestinal tract implying rapid excretion of T-2588. When (pivaloyloxymethyl-14C) T-2588 was orally administered, radioactivity was accumulated to all tissues and fetus. From these results we speculated that formaldehyde formed by hydrolysis at the pivaloyloxymethyl ester and entered the C1-metabolic pathway.