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St. John's Wort Side Effects, Interactions and Warnings



  • Consult a doctor or an herbalist before using St. John's Wort.

    If you are pregnant or lactating or taking any other anti-depressants like Prozac, check with your physician before taking St. John's wort. It is not effective for severe depression, and no one should stop taking any prescribed medications for depression without proper medical care.

  • High blood pressure, headaches, stiff neck, nausea, and vomiting. In the fair-skinned, it can exacerbate sunburn and cause blistering after sun exposure.

  • Avoid the following substances when using St. John's Wort: Amino acids tryptophan and tyrosine; amphetamines; asthma inhalants; beer, coffee, wine; chocolate, fava beans, salami, smoked or pickled foods, and yogurt; cold or hay fever medicines; diet pills; narcotics; nasal decongestants. They all contain chemicals that react adversely to hypericin, causing high blood pressure and nausea.
    - Murray, M. -- The Pill Book Guide to Natural Medicines: Vitamins, Minerals, Nutritional Supplements, Herbs, and Other Natural Products. -- Bantam, 2002. 786.

  • Interferes with the absorption of iron and other minerals.

  • St. John's wort should not be taken with any other antidepressants.
    - Murray, M. -- The Pill Book Guide to Natural Medicines: Vitamins, Minerals, Nutritional Supplements, Herbs, and Other Natural Products. -- Bantam, 2002. 784.

  • St. John's wort should be taken with meals.

  • If co-medication with coumarin-type anticoagulants is unavoidable, it must only be undertaken provided the physician closely monitors clotting parameters.
    - Murray, M. -- The Pill Book Guide to Natural Medicines: Vitamins, Minerals, Nutritional Supplements, Herbs, and Other Natural Products. -- Bantam, 2002. 785.

  • Co-medication with ciclosporin and indinavir, and for the time being, other protease inhibitors used in anti-HIV treatment, is absolutely contraindicated.
    - Incidence and clinical relevance of the interactions and side effects of Hypericum preparations. -- Schulz V. -- Phytomedicine. 2001 Mar;8(2):152-60.

  • In transplant patients, self-medication with St John's wort (Hypericum perforatum) has led to a drop in plasma levels of the immunosuppressant drug cyclosporine, causing tissue rejection.
    - Xenobiotica 2002 -- Jun;32(6):451-78 -- Pharmacokinetic interactions between herbal remedies and medicinal drugs. -- Ioannides C.

  • Causes intermenstrual bleeding, delirium or mild serotonin syndrome, respectively, when used concomitantly with oral contraceptives (ethinylestradiol/desogestrel), loperamide or selective serotonin-reuptake inhibitors (sertaline, paroxetine, nefazodone).
    - Drugs 2001;61(15):2163-75 -- Interactions between herbal medicines and prescribed drugs: a systematic review. -- Izzo AA, Ernst E.

  • Because the majority of people who take this popular over-the-counter preparation do so without formal psychiatric evaluations, risk of hypericum-induced mania may be significant. Physicians should screen patients for a history of hypomania or mania before recommending use of St. John's wort.
    - Biol Psychiatry 1999 Dec 15;46(12):1707-8 -- Mania associated with St. John's wort. -- Nierenberg AA, Burt T, Matthews J, Weiss AP.

  • St. John's wort may cause serotonin syndrome in sensitive patients. In addition, St John's wort may be associated with hair loss. For clinical reasons, it is important to recognize and report adverse reactions to herbal remedies and to document that these treatments have side effects commensurate with their potent action on brain neurochemistry.
    - Can J Psychiatry 2001 Feb;46(1):77-9 -- Adverse reactions to St John's Wort. -- Parker V, Wong AH, Boon HS, Seeman MV.

  • Results support the notion that hyperforin interferes with the storage of monoamines in synaptic vesicles
    - Life Sci 2002 Sep 27;71(19):2227-37 -- Inhibition of vesicular uptake of monoamines by hyperforin. -- Roz N, Mazur Y, Hirshfeld A, Rehavi M.

  • Because of the potential for side-effects and drug interactions it is important for anaesthetists to be aware of use.
    - Br J Anaesth 2002 Nov;89(5):792-5 -- Preoperative use of herbal medicines: a patient survey. -- Skinner CM, Rangasami J. -- Royal Berkshire Hospital, Reading, UK.





  • 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. Possible pharmacodynamic interactions with selective serotonin re-uptake inhibitors and serotonin receptor-agonists such as triptans used to treat migraine were identified. These interactions are associated with an increased risk of adverse reactions.
    - Br J Clin Pharmacol 2002 Oct;54(4):349-56 -- St John's wort (Hypericum perforatum): drug interactions and clinical outcomes. -- Henderson L, Yue QY, Bergquist C, Gerden B, Arlett P.

  • St. John's Wort contains photosensitizing substances, which, at high dose, or during chronic use, may provoke intense dermatitis or photosensitivity. The potential occurrence of side effects with its use has led the European Agency for drug assessment and the French Medicines Agency to decree that all magistral preparations containing St. John's wort must be labeled: "Warning, risk of drug interactions".
    - Presse Med 2002 Sep 21;31(30):1416-22 -- Metabolic effects and drug interactions provoked by certain vegetables: grapefruit, St. John's wort and garlic -- Neuman M.

  • St. John's wort extract has a clear inhibitory effect on the neuronal uptake not only of serotonin, noradrenaline, and dopamine but also of gamma-aminobutyric acid (GABA) and L-glutamate.
    - Pharmacol Res 2003 Feb;47(2):101-9 -- Current St. John's wort research from mode of action to clinical efficacy. -- Muller WE.

  • St. John's wort has the potential to alter medication pharmacokinetics and the seizure threshold.
    - 2001 Dec;2(6):524-532 -- Herbal Medicines and Epilepsy: The Potential for Benefit and Adverse Effects. -- Spinella M.

  • St John's wort enormously decreases the plasma concentrations of omeprazole.
    - Clin Pharmacol Ther. 2004 Mar;75(3):191-7. -- St John's wort induces both cytochrome P450 3A4-catalyzed sulfoxidation and 2C19-dependent hydroxylation of omeprazole. -- Wang LS, Zhou G, Zhu B, Wu J, Wang JG, Abd El-Aty AM, Li T, Liu J, Yang TL, Wang D, Zhong XY, Zhou HH.

  • The majority of websites rated poorly with a concerning lack of information about the interaction between hypericum and warfarin, anti-depressants and oral contraceptives. Most sites also failed to provide sufficient information about the contraindications and adverse effects of hypericum treatment.
    - Complement Ther Med. 2011 Jun;19(3):155-60. Epub 2011 May 25. -- The quality of information on websites selling St. John's wort. -- Thakor V, Leach MJ, Gillham D, Esterman A.

  • Well-documented SJW interactions include (1) reduced blood cyclosporin concentration, as suggested by multiple case reports as well as by clinical trials, (2) serotonin syndrome or lethargy when SJW was given with serotonin reuptake inhibitors, (3) unwanted pregnancies in women while using oral contraceptives and SJW, and (4) reduced plasma drug concentration of antiretroviral (e.g., indinavir, nevirapine) and anticancer (i.e., irinotecan, imatinib) drugs. Hyperforin, which is believed to contribute to the antidepressant action of St John's wort, is also strongly suspected to be responsible of most of the described interactions.
    - AAPS J. 2009 Dec;11(4):710-27. Epub 2009 Oct 27. -- Herb-drug interactions with St John's wort (Hypericum perforatum): an update on clinical observations. -- Borrelli F, Izzo AA.



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last update: February 2014



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