Reported pharmacological interactions of common herbal preparations with prescription medication from Medical Journal of Australia Feb 2017

St John’s Wort

• interferes with cyclosporine used to maintain transplants leading to rejection
• causes intermenstrual bleeding  for women using the oral contraceptive
• reduces effectiveness of warfarin
• reduces bioavailability of theophylline , amitriptyline,, methadone, digoxin
• potentiates side effects of tricyclic and SSRI antidepressants

Asian Ginseng

• reduces effectiveness of immunosuppressive drugs
• increases effects of oral hypoglycaemic ( diabetes ) drugs
• increases side effects of MAOI antidepressants
• has accumulative effect on benzodiazepines ( Valium, Serepax)

Garlic

• increases liver toxicity of paracetamol
• increases effects of oral hypoglycaemic ( diabetes ) drugs
• increases incidence of bleeding in users of anticoagulant medication

Evening Primrose  Oil

• lowers the seizure threshold  for  epileptics
• interferes with the action of  some anticonvulsants  including phenytoin ( Dilantin)

Dong Quai

• potentiates   warfarin