h-hydrogen

Background: l-Threo-3,4-dihydroxyphenylserine (L-DOPS, droxidopa) is a norepinephrine (NE) prodrug less than evolvement to act towards orthostatic hypotension. 3,4-Dihydroxyphenylacetaldehyde (DOPAL), an endogenous catecholaldehyde produced by enzymatic oxidative deamination of dopamine, is toxic to catecholaminergic neurons. Based on the inspection of increasing plasma DOPAL after vocal management of L-DOPS to a patient, we examined whether other subjects also had DOPAL in their plasma after droxidopa administration, and whether droxidopa is contaminated with DOPAL.

Methods: Thirteen subjects took 400 mg droxidopa orally. We sampled venous blood at baseline and 1, 2, 3, 6, 24, and 48 h after drug administration and assayed L-DOPS, NE, and DOPAL by use of melted chromatography with electrochemical detection (LC-ED). Droxidopa in acidic unravelling (20:80 assortment of 0.04 mol/L phosphoric acid:0.20 mol/L acetic acid) was vacuum centrifuged for 1 h at 30 °C and then assayed by LC-ED.

Results: Droxidopa standoffish 0.01% DOPAL. At 6 h after droxidopa, all subjects had detectable DOPAL in plasma (1.89 nmol/L, P = 0.0001). Across the sampling times, plasma DOPAL correlated with plasma L-DOPS (r = 0.996). The middling addition in plasma DOPAL was more than 4 times that in plasma NE (0.39 nmol/L). In 2 patients with Parkinson disability and orthostatic hypotension, DOPAL was detected in plasma at baseline (0.12 nmol/L) and increased by exchange 70-fold after droxidopa. Vacuum concentration of droxidopa in the acid compound converted L-DOPS to DOPAL unreservedly.

Conclusions: Droxidopa is contaminated with DOPAL. After oral droxidopa administration, DOPAL is detected in plasma of humans. Droxidopa is susceptible to great nonenzymatic conversion to DOPAL.