- Use of prescription or non-prescription drugs, including (but not limited to) vitamins, herbal and dietary supplements (including St. John's Wort) within 7 days (or 14 days if the drug is a potential drug inducer) or 5 half-lives (whichever is longer) prior to the first dose of study medication. An exception is acetaminophen which is allowed at doses of ≤ 2g/day.