St. John's Wort Side Effects & Warnings

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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.

Avoid exposure to the sun during treatment, it can cause heightened sun sensitivity when taken in large amounts. Anyone who is hypersensitive to sunlight or is taking other photosensitizing drugs should be cautious.

Interferes with the absorption of iron and other minerals

St. John's wort should not be taken with any other antidepressants

St. John's wort should be taken with meals

Hypericum preparations must not be taken at the same time as other antidepressants.

If co-medication with coumarin-type anticoagulants is unavoidable, it must only be undertaken provided the physician closely monitors clotting parameters.

Co-medication with ciclosporin and indinavir, and for the time being, other protease inhibitors used in anti-HIV treatment, is absolutely contraindicated.

In transplant patients, self-medication with St John's wort (Hypericum perforatum) has led to a drop in plasma levels of the immuno suppressant drug cyclosporine, causing tissue rejection.

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.

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.

Results support the notion that hyperforin interferes with the storage of monoamines in synaptic vesicles.

Because of the potential for side-effects and drug interactions it is important for anaesthetists to be aware of use.

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.

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".

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.

St. John's wort has the potential to alter medication pharmacokinetics and the seizure threshold.
St John's wort enormously decreases the plasma concentrations of omeprazole.


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