DL-Threo-3,4-dihydroxyphenylserine does not exert a pressor effect in orthostatic hypotension

DL-Threo-3,4-dihydroxyphenylserine (DL-DOPS) was given to six subjects with severe orthostatic hypotension (OH). On separate days each subject took either 600 or 800 mg DL-DOPS or placebo. DL-DOPS increased norepinephrine (NE) excretion 10,000% and urinary normetanephrine and dihydroxyphenylglycol excretion 400%. DL-DOPS, however, led to only slight increases in excretion of the major NE metabolites 3-methoxy-4-hydroxyphenylglycol and vanillylmandelic acid. Only approximately 2.2% +/- 0.5% (range 0.65% to 3.8%) of the L-stereoisomer (L-DOPS), when given as DL-DOPS, is converted to NE in vivo over 24 hr. DL-DOPS did not affect either supine or upright blood pressure in our subjects. Our findings do not support reports that DL-DOPS may be therapeutically useful in OH.