Multiple studies with oral contraceptives, warfarin, protease inhibitors, reverse transcriptase inhibitors, simvastatin, atorvastatin, verapamil, irinotecan, imatinib, methadone, cyclosporin, tacrolimus, fexofenadine, nifedipine, midazolam, omeprazole, voriconazole

Evidence suggests this interaction is likely to occur in most patients

Depending on drug and disease state

CYP450 enzyme substrate (CYP2C19, CYP3A4) 

Human study of the various CYP enzymes

Evidence suggests this interaction might occur in some patients

CYP450 enzyme substrates (CYP2B6, CYP2C9, CYP2E1 and CYP 1A2) 

Intervention by a healthcare professional may be required

Digoxin

Clinical trials - interaction seen at doses over 2 g/d (dried herb)

P-glycoprotein substrates

In vitro and/or animal evidence with unclear implications, however, it cannot exclude the possibility of occurring in humans

Pethidine and dextromethorphan

Case study of aminolevulinic acid. In vitro study

Photosensitising drugs

Multiple case reports of serotonergic syndrome. Human study in patients taking amitriptyline. Case report of monoxidase activity

Clinical evaluation by a healthcare professional is recommended to assess the degree of intervention required

St John's wort