Dopamine and norepinephrine are chemicals called catecholamines. The most well-known member among this group is adrenalin, also known as epinephrine, which is a "fight or flight" hormone. Dopamine and norepinephrine are found in the brain, spinal cord and as signals in the blood. They occur naturally in the body and can be given intravenously as medications in certain conditions. The management of medical conditions should be undertaken with the consultation of a physician or other qualified health care professional.
Endogenous Dopamine
Endogenous dopamine means dopamine naturally found in the body. In the brain, it plays a role in movement, thinking, motivation, punishment and reward. Certain areas of the brain have low dopamine activity in Parkinson's Disease, leading to a movement disorder. Many addictive drugs reinforce the effects of dopamine in key areas of the brain, leading to feelings of reward and motivation to seek the drug.
Prescription Dopamine
The blood vessels in the brain restrict what kinds of chemicals can pass from the blood into the brain, this is called the blood-brain barrier. Dopamine can be delivered to the body intravenously, but it does not cause effects in the brain due to the blood-brain barrier. Prescription dopamine is given in shock. Shock does not refer to an emotional reaction; it is a state in which the organs do not receive enough blood and oxygen and begin to malfunction. Some causes of shock can be treated with dopamine. It increases the heart rate and blood pressure to provide more blood and oxygen to the organs, which helps support bodily function while the underlying cause of shock is addressed.
Endogenous Norepinephrine
Like dopamine, endogenous norepinephrine acts on the nerves. It acts as a neurotransmitter, affecting nerves nearby where it has been released, and as a hormone that acts over long distances. Norepinephrine is synthesized from dopamine in the body. Whereas dopamine acts largely on movement and reward, norepinephrine is a stress hormone. It increases attention and the fight or flight response.
Prescription Norepinephrine
Norepinephrine also is given in shock to increase the delivery of blood to the organs, mostly by decreasing the diameter of the blood vessels and, therefore, increasing the blood pressure. Some clinicians prefer to start with one over the other, and the decision is individualized to the patient's condition. A 2010 study in the "New England Journal of Medicine" concluded that there was no significant difference in the rates of death between dopamine and norepinephrine overall. However, when heart failure was the cause of shock, there was an increased risk of death for dopamine use alone compared to norepinephrine use alone. In addition, dopamine was associated with more adverse events, such as disturbances in the heart rhythm.
References
- "Neuroscience"; Dale Purves; 4th Ed., 2007
- "Harrison's Principles of Internal Medicine"; Anthony S Fauci, et al.; 17th Ed., 2008
- "Physiology"; Linda S.Costanzo; 4th Ed., 2008
- "New England Journal of Medicine"; "Comparison of Dopamine and Norepinephrine in the Treatment of Shock"; D. De Backer, et al; 2010
