The nerve endings in the body naturally produce serotonin, a chemical that plays an important regulatory role in the brain. The level of serotonin in the body can affect many systems and bodily organs. Many drugs available on the market increase serotonin levels such as antidepressants known as selective serotonin reuptake inhibitors. Other drugs that increase serotonin levels include selective serotonin/norepinephrine reuptake inhibitors, monoamine oxidase inhibitors and triptans used to treat migraines. The constellation of symptoms that result from increased levels of serotonin is collectively known as the serotonin syndrome.
Mental Complications
The Merck Manuals Online Medical library lists restlessness, confusion, agitation, hallucinations, anxiety and easy startling as potential complications of increased serotonin levels in the body. These symptoms are due to the stimulatory effects of serotonin on the central nervous system. The hyper-stimulation can even result in seizures in extreme cases.
Excessive Nerve Cell Activity
According to the American Headache Society, excess serotonin can cause excessive stimulation of the nervous system causing the characteristic muscular symptoms of serotonin syndrome. For instance, muscle spasms known as myoclonus, hyper-reactive reflexes, shivering and tremors are all common symptoms of serotonin syndrome that result from the stimulation of skeletal nerve endings which in turn stimulate muscular contraction. These effects are usually more apparent in the lower limbs than the arms. This excessive muscular stimulation may result in a potentially fatal condition involving muscle breakdown called rhabdomyolysis. Rhabdomyolysis can result in acute kidney failure.
Autonomic Nervous System Hyperactivity
The Merck Manuals Online Medical library discusses the dangers of increased serotonin on the control of blood pressure and heart rate; the serotonin syndrome is usually associated with an increased heart rate and a rise in blood pressure. This is because serotonin also stimulates the nerve endings of the autonomic nervous system. The autonomic nervous system is the master control systemof involuntary body functions. Its excessive stimulation causes an increase in heart rate, elevated blood pressure, nausea, vomiting, diarrhea and excessive sweating or diaphoresis.
