- Use of prescription or non-prescription drugs, including vitamins, herbal and dietary supplements (including St John's Wort) within 7 days (or 14 days if the drug is a potential enzyme inducer) or 5 half-lives (whichever is longer) before the first dose of study medication, unless in the opinion of the investigator and GlaxoSmithKline (GSK) Medical Monitor the medication will not interfere with the study procedures or compromise subject safety.