15. Use of substances known to be strong inhibitors or inducers of cytochrome P450 enzymes (eg, ritonavir, ketoconazole, nefazodone, grapefruit juice) within 14 days prior to the first dose of study drug through the last study visit. Chronic exposure to enzyme inducers such as paint solvents or pesticides, other investigational drug use, or illicit drug use within 30 days prior to study drug administration;