If you take a medicine and then you increase the dose of such a drug or add a new drug to the ones you take already, 
and not long after that you have a rapid heart rate, confusion, agitation, heavy sweating, shivering etc maybe you should consider yourself of having a Serotonin Syndrome. Herein is the article that will describe you about this condition.
Serotonin is one of three monoamine neurotransmitters most often associated with depression and is needed for your nerve cells and brain to function, of course if it is not too much. Serotonin may also be associated or involved in conditions such as migraine headaches and anxiety while correct serotonin concentrations can greatly improve quality of life, according to the article.
Another sections of the article describe about Pharmacology and Physiology of the serotonin, Signs and symptoms of Serotonin Syndrome, what medications that increase serotonin (including meperidine), Comparison of Serotonin Syndrome and Neuroleptic Malignant Syndrome (NMS), how to diagnose, and the treatment of life threatening serotonin syndrome.
Download the article of Life Threatening Serotonin Syndrome particularly for health professionals (source: uuhsc.utah.edu).
