Norepinephrine is a naturally occurring hormone produced in the medulla and secreted by the adrenal glands. It is a neurotransmitter or “chemical messenger” that enables nerve cells to communicate with one another. Norepinephrine is a relative of adrenalin or epinephrine. When a person is excited or afraid, the adrenal glands secrete a hormonal mix of 80% epinephrine and 20% norepinephrine. The effect of norepinephrine is to raise the heart rate, which in turn causes glucose to be released, increasing the person’s energy levels and blood flows. These two hormones are engaged in the “fight or flight” response, which means if a person feels threatened, he will either stay and fight or run away. In either case, he needs more energy and increased blood flow, providing by the rush of norepinephrine and adrenalin. Norepinephrine, manufactured under the brand name Levophed, is also used as a drug to treat low blood pressure in children. It comes as an injection and works by stimulating the heart. Serotonin and norepinephrine reuptake inhibitors (SNRIs) are drugs that relieve depression and anxiety by blocking the absorption of both serotonin and norepinephrine in the brain, and by affecting other neurotransmitters.