St John's wort (Hypericum perforatum): drug interactions and clinical outcomes

Abstract

AimsThe aim of this work is to identify the medicines which interact with the herbal remedy St John's wort (SJW), and the mechanisms responsible. Methods A systematic review of all the available evidence, including worldwide published literature and spontaneous case reports provided by healthcare professionals and regulatory authorities within Europe has been undertaken. Results A number of clinically significant interactions have been identified with prescribed medicines including warfarin, phenprocoumon, cyclosporin, HIV protease inhibitors, theophylline, digoxin and oral contraceptives resulting in a decrease in concentration or effect of the medicines. These interactions are probably due to the induction of cytochrome P450 isoenzymes CYP3A4, CYP2C9, CYP1A2 and the transport protein P-glycoprotein by constituent(s) in SJW. The degree of induction is unpredictable due to factors such as the variable quality and quantity of constituent(s) in SJW preparations. In addition, possible pharmacodynamic interactions with selective serotonin re-uptake inhibitors and serotonin (5-HT 1d ) receptoragonists such as triptans used to treat migraine were identified. These interactions are associated with an increased risk of adverse reactions. Conclusions In Sweden and the UK the potential risks to patients were judged to be significant and therefore information about the interactions was provided to health care professionals and patients. The product information of the licensed medicines involved has been amended to reflect these newly identified interactions and SJW preparations have been voluntarily labelled with appropriate warnings.

In Vitro Evaluation of Metabolic Drug–Drug Interactions: Concepts and Practice

“…An example of pharmacological Henderson et al (2002) interactions is serious, sometimes fatal drop in blood pressure due to coadministration of nitroglycerin and sedfenadil (Schalcher et al, 2002).…”

Evaluation of the Light-Sensitive Cytotoxicity of Hypericum perforatum Extracts, Fractions, and Pure Compounds

“…The efficacy of SJW as an antidepressant has been extensively studied along with its safety (1)(2)(3)(4)(5)(6). The clinical and animal trials conducted thus far demonstrate Hp extracts to be just as effective as tricyclic antidepressants with fewer shortterm side effects, but recent evidence of drug-herb interactions involving the hepatic cytochrome P450 enzyme system may be one of several adverse reactions to this herb that need to be elucidated before it can be deemed a safe form of alternative medicine (1)(2)(3)(4)(5)7).…”

Essentials of Herb-Drug Interactions in the Elderly With Cardiovascular Disease

“…138 Reduced levels of digoxin also have been reported. 139 St. John's wort can alter anticoagulation properties of warfarin resulting in unstable INR values, 140 and bleeding complications were reported in elderly taking warfarin 141 (Table 2 and Online Supplemental Appendix 1). It can cause hypertensive crisis with foods rich in tyramine.…”