- Persons undergoing the autonomic testing will be asked to refrain from smoking, caffeine, alcohol and vigorous exercise 24 hours before the study. Several medications should not be taken 48 hours prior to the study; these include tricyclic antidepressants, antihistamines, cough and cold medications, anti-Parkinson medication, muscle relaxants, anti-psychosis medications, opioid drugs, and blood pressure medications. No one is to stop their prescribed medication without discussion with their primary care physician though the ability to complete all of the autonomic testing may be affected.