3-methoxy-4-hydroxyphenylglycol-sulfate and cimoxatone

Prolactin (PRL) secretion is stimulated by serotonin (5-HT) and inhibited by dopamine (DA). 5-HT is generally recognized as a substrate for type A monoamine oxidase (MAO), whereas DA is considered as a substrate for either A or B, or both forms of MAO, depending on the species and tissues used. The effect of cimoxatone, a reversible, selective MAO-A inhibitor, on diurnal variation in plasma PRL level was investigated in healthy adults after a single 40 mg oral dose, as an indirect approach to investigating whether DA is preferentially a substrate for Type A or B MAO in man. The circadian rhythm in PRL, stress conditions and diet were taken into account in the present study, which was placebo-controlled. There was a slight but significant reduction in circulating PRL in the six subjects, which persisted for at least 9 h after cimoxatone. However, the duration of the decrease in plasma PRL was shorter than the inhibition of MAO-A. The results are not inconsistent with the presence of both forms of MAO in the human hypothalamus and with DA as a substrate for both forms in this region, if it is assumed that the hypothalamic concentrations of the drug during the period 0-9 hours was sufficiently high to inhibit DA deamination by both forms of MAO.

Topics: Adult; Circadian Rhythm; Humans; Hydrocortisone; Kinetics; Male; Methoxyhydroxyphenylglycol; Monoamine Oxidase Inhibitors; Oxazoles; Oxazolidinones; Prolactin

Cimoxatone is a new monoamine oxidase inhibitor (MAOI) in comparison to the existing non-selective and irreversible MAOIs used in the therapy of depression. A clinical study has been carried out in 10 depressed patients. Cimoxatone was given from 0.32 to 0.78 mg/kg/day for 28 days. The drug was shown to be effective against depression and well tolerated at the given doses. The inhibition of monoamine oxidase and its reversibility were assessed by urinary excretion of 3-methoxy-4-hydroxy- phenylethyleneglycol sulphate. The treatment had no effect on the plasma prolactin levels. The plasma concentrations of cimoxatone reached a plateau after 3 to 4 days of therapy. The study confirmed earlier findings in healthy volunteers that the principal metabolite is also active as a type A MAOI. The plasma elimination of cimoxatone and its metabolite is almost complete 4 days after the last dosing.

Topics: Adult; Clinical Trials as Topic; Depressive Disorder; Female; Humans; Kinetics; Male; Methoxyhydroxyphenylglycol; Middle Aged; Monoamine Oxidase Inhibitors; Oxazoles; Oxazolidinones; Prolactin