Low blood pressure with increased heart rate. Possibly obtunded or even agitated.
This has the potential to be a sodium channel blocker (class I antiarrhythmics like quinidine, lidocaine or flecainide) or a tricyclic antidepressant (TCA) like amitriptyline. The problem these drugs have is the effect on the heart's electrical activity and we have to look very closely at whether or not the drug is lengthening the electrical cycle or increasing the heart rate.
Couple this with ringing in the ears (if the patient can tell you) and you likely have an aspirin overdose. Aspirin overdoses are the second leading cause of death behind Tylenol overdoses.
Nausea, vomiting and diarrhea coupled with slow mentation and tremors.