CITALOPRAM is an antidepressant in a group of drugs called Selective Serotonin Reuptake Inhibitors (SSRIs).

SSRIs mechanism of action is on Serotonin, a hormone also called 5-hydroxytrptamine, found in the pineal gland, blood platelets, digestive tract and the brain. Serotonin acts as both a chemical messenger that transmits nerve signals between nerve cells and causes the blood vessels to narrow.  Serotonin makes blood clots form and is a muscle as well as a vasoconstrictor, but it also plays an important role in sleep, appetite, memory, aggression, sexual behavior, cardiovascular activity, respiratory activity, motor output, neuroendocrine and sensory function, and perception. According to Dr. Ann Blake Tracy, an increase in Serotonin produces rushes of insulin that drops blood sugar levels and can create a chemically induces hypoglycemia (low blood sugar). Additionally, too much Serotonin damages blood vessels, particularly in the lungs and may adversely affect heart valves. This is because Serotonin is a powerful vasoconstrictor (narrows the blood vessels).

Consistently elevating Serotonin levels causes the stress hormones Cortisol and Adrenaline (Epinephrine) in the body and brain to be triggered by the adrenal glands. This natural reaction is the body’s way to combat the excessive Serotonin levels. This boost produces a euphoric state and can be viewed as a lessening of depression. However, prolonged increases in Serotonin can cause adrenal exhaustion, where the Adrenals lose their efficiency, causing adrenaline to fall while Cortisol rises. Ultimately the Cortisol levels fall and lead to fatigue. Many SSRI users report fatigue, and it can take time for the Adrenal Glands to restore normal adrenaline levels after stopping antidepressants.

The eyes have significant levels of Melatonin, and the precursor to Melatonin is Serotonin, which is derived from the amino acid tryptophan, which converts to 5-HTP first and then to Serotonin. Within the pineal gland, Serotonin is used to yield melatonin. Therefore, Serotonin also dramatically alters the sleep-wake cycle since Serotonin activity gradually decreases as one becomes drowsy and enters slow wave sleep (non-REM sleep). During REM sleep (Rapid Eye Movement), or dream sleep, Serotonin activity falls completely silent. It returns to its basic level several seconds prior to the end of REM sleep, which occurs in 90-100 minute cycles. REM alternates with Non-REM about 4-5 times during the night.  During non-REM sleep, there is a lot of movement, but during REM sleep, only the eye muscles move. This may explain why so many SSRI users report bizarre, vivid dreams.

It is estimated that 95% of our Serotonin is produced in the gut region, where it triggers digestion. Nerve cells in the gut also use Serotonin to signal back to the brain, where it trains us not to eat certain foods by communicating pain and gas. This second brain is an independent network of over 100 billion neurons that signals our bodies to stress, but can also cause illness if the stomach is unhealthy, since the majority of our immune cells line the gut walls. The high concentration of Serotonin in the stomach region is why antidepressants commonly have side effects that include nausea, weight gain and stomach upset.