Page "Dopamine" Paragraph 3

Dopamine is available as an intravenous medication acting on the sympathetic nervous system, producing effects such as increased heart rate and blood pressure.

However, because dopamine cannot cross the blood – brain barrier, dopamine given as a drug does not directly affect the central nervous system.

To increase the amount of dopamine in the brains of patients with diseases such as Parkinson's disease and dopa-responsive dystonia, L-DOPA ( the precursor of dopamine ) is often given because it crosses the blood – brain barrier relatively easily.