Droxidopa is a synthetic amino acid precursor which acts as a prodrug to the neurotransmitters norepinephrine (noradrenaline) and epinephrine (adrenaline) and it is used to increase the concentrations of these neurotransmitters in the body and brain. Unlike norepinephrine and epinephrine themselves, droxidopa is capable of crossing the protective bloodÂ–brain barrier (BBB). It is metabolized by aromatic L-amino acid decarboxylase (AAAD), also known as DOPA decarboxylase (DDC). Droxidopa works by increasing the levels of norepinephrine and epinephrine in the peripheral nervous system (PNS), which induces tachycardia or increased heart rate and hypertension or increased blood pressure, thus enabling the body to maintain blood flow upon and while standing. (Source: http://en.wikipedia.org/wiki/Droxidopa).