AUTORADIOGRAPHIC DISTRIBUTION STUDY OF "SHORT ACTING" AND "LONG ACTING" BARBITURATES: 35S-THIOPENTONE AND 14C-PHENOBARBITONE

The distribution of ³⁵S-thiopentone and ¹⁴C-phenobarbitone hasbeen studied after intravenous injection in the mouse wholebody and in the cat brain, using an auto-radiographic technique.Thirty seconds after injection ³⁵S-thiopentone reached the highestconcentration in the brain and liver of the mice, leaving theblood very rapidly. The adipose tissue built up increasing levelsof radioactivity up to 20 minutes after the injection of ³⁵S-thiopentone.¹⁴C-phenobarbitone showed a more even distribution in parenchymatousand lean tissues. A rather constant level of radioactivity waspresent in the blood during 4 hours after the administrationof ¹⁴C-phenobarbitone. ¹⁴C-pheno-barbitone penetrated the bloodbrain barrier at a much slower rate than ³⁵S-thiopentone. Thebrain distribution of both compounds was studied in furtherdetail in the cat brain. Experiments with pregnant mice revealedsome differences in the placental passage and foetal distributionof these two barbiturates.