- Use of prescription or non-prescription drugs, including vitamins, herbal and dietary supplements within 7 days or 5 half-lives (whichever is longer) prior to the first dose of study medication, or use of St. John's Wort within 14 days prior to the first dose of study medication. By exception, the volunteer may take paracetamol or acetaminophen (<=2 grams/day) up to 48 hours prior to the first dose of study medication. However, the Investigator and GSK study team can review medication on a case by case basis to determine if its use would compromise subject safety or interfere with the study procedures or data interpretation.