4'-Hydroxylated derivatives as urinary metabolites of two barbiturates

4'-Hydroxybutobarbitone and 4'-hydroxypentobarbitone have been synthesized. These 4'-hydroxy derivatives have been quantified in the urine of volunteers following single doses of butobarbitone, and single and multiple doses of pentobarbitone. The corresponding aldehydes have also been synthesized, and shown to be excreted in minor quantities. The excretion of an ingested dose of 4'-hydroxybutobarbitone, and its oxidation products, has also been followed over 24 h.

Metabolism of quinalbarbitone

The human metabolism of (+/-)-5-allyl-5-(1'-methylbutyl) barbituric acid (I), quinalbarbitone, taken orally, has been studied. Comparison of g.c. and g.c.-m.s. data from derivatized extracts of urine with similar data from synthetic samples confirmed the presence of the two diastereoisomeric forms of 5-allyl-5-(3'hydroxy-1'-methylbutyl)barbituric acid (II), 5-allyl-5-(3'-oxo-1'-methylbutyl)barbituric acid (III), 5-allyl-5-(1'-methyl-3'-carboxypropyl)barbituric acid (IV), and 5-(2',3'-dihydroxypropyl)-5-(1'-methylbutyl)barbituric acid (V) in the urine. There was no evidence for the urinary excretion of unchanged drug. The rate of excretion of these metabolites has been examined in some detail, and rate-limited kinetics shown to apply for excretion of the acid (IV) and the diol (V).

Metabolism of nealbarbitone

The human metabolism of 5-allyl-5-neopentylbarbituric acid (nealbarbitone, Censedal), taken orally, has been studied. Comparison of the gas chromatography—mass spectra of extracts from urine with the spectra of model compounds showed nealbarbitone diol (III) to be the only urinary metabolite present in significant amount (about 30–40% of dose); the rate of excretion of diol reached a maximum about 36 h after ingestion of a single 300 mg dose. Treatment of nealbarbitone with a model oxidase of the Udenfriend type resulted only in oxidation of the allyl side-chain to the 2-oxopropyl derivative, in low yield.