Mass fragmentographic assay of nanogram amounts of the antidepressant drug mianserin hydrochloride (Org GB 94) in human plasma.

For the assay of the antidepressant compound mianserin hydrochloride (Org GB 94) in human plasma, a mass fragmentographic method, using the deuterated analogue as internal standard and a high-performance liquid chromatographie sample clean-up procedure has been developed. The assay specifications obtained are a lower limit for reliable measurements of 1 ng/ml, and accuracy of ca. 0.01 ng/ml, a precision of 6--7% and a capacity of about 60 samples per day. The applicability of the assay method is illustrated by measurements of single-dose and steady-state plasma levels in clinical experiments, demonstrating the possibility of monitoring plasma levels during at least 24 h after a single dose of 15 mg of Org GB 94. The mean steady-state plasma levels after a daily dose of 3 X 20 mg of Org GB 94 appeared to be remarkably constant with time: 38, 36 and 34 ng/ml after 2, 4, and 6 weeks of treatment of 18 depressed patients.