Clinical studies on norepinephrine metabolism: how to interpret the numbers

Metabolism, synthesis rates, and pharmacokinetics of major metabolites of endogenous norepinephrine were investigated in 38 drug-free depressed patients receiving a low monoamine diet on a closed ward. In a group of 21 patients, plasma and cerebrospinal fluid (CSF) concentrations of 3-methoxy-4-hydroxyphenyl-glycol (MHPG) correlated positively, but not significantly. In two groups of eight patients each, effects of desipramine and zimelidine on the central production rate of MHPG were examined using CSF and urine data. Both desipramine and zimelidine significantly reduced the central production rate of MHPG.