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Well, since you are taking Tramadol alone , and there are no SSRI OR SNRI anti depressants which you are taking along with it , so it is not possible that you are suffering from Serotonin syndrome , as Tramadol alone cannot cause it , so relax and do not worry .
The symptoms as of now seem to be once in a while kind of troublesome symptoms , which are unlikely to occur again, but , if they occur again then the possible reason behind their occurrence can be the side effects of Tramadol , but not Serotonin syndrome , so in that case just get tramadol dose reviewed by your doctor who has placed you on it. But , untill a repeat of the symptoms that occurred last night occurs , just relax , and wait and watch , i am quite sure you will not experience those symptoms again as such symptoms can ocuur once in a blue moon , without any serious underlying cause to support them.
I am mentioning below links to Serotonin syndrome and tramadol , just go through them once , this will probably throw more light on them and help you to understand that your symptoms were not related to Serotonin syndrome.
I wish you best of health.
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