Assay for cyclo-, seco- and pentobarbital by multiple ion detection: kinetics after a single dose.

A sensitive assay for the determination of four different barbiturates: butabarbital, cyclobarbital, pentobarbital and secobarbital is described. The barbiturates are determined quantitatively by gas chromatography/mass spectrometry (GC/MS) as their dimethylated derivatives. The sensitivity of this simple procedure is limited to 10 x 10(-6) g/l for cyclo- and secobarbital and 1 x 10(-6) g/l for pentobarbital in plasma. The assay has been used to measure the kinetics of pentobarbital over 6 days after a single 50 mg dose of the sodium salt, and over 3 days for one combined preparation of 25 mg cyclobarbital-calcium and 75 mg secobarbital-sodium. The corresponding barbiturate levels in saliva were determined by the same assay.