- Use of prescription or nonprescription drugs, vitamins and dietary supplements within 7 days or 5 half-lives (whichever is longer) prior to the first study period. As an exception, analgesics, caffeine, and non-pharmacological methods may be used on the discretion of the investigator to manage symptoms related to the lumbar catheterization. Aspirin, aspirin containing products, and non-steroidal anti-inflammatory agents that affect platelet function should not be used. Other exceptions may be granted by a qualified member of Pfizer study management.