Interactions of St. John’s wort with other substances

St. John’s wort and the pill – is it compatible? Can St. John’s wort be combined well with other medicines? Is it allowed to consume alcohol during St. John’s therapy?

St. John’s wort contains, in addition to the active ingredients hyperforin and hypericin, numerous ingredients that act on the enzymes (family of cytochrome P450 monooxygenases) of the liver. In particular, the activity of the enzyme CYP3A4 is significantly increased, through which approximately half of all drugs are metabolized. As a result, a combination of these drugs with St. John’s wort can lead to considerable interactions.

Both significantly increased quantities of a drug and significantly decreased concentrations of an active ingredient in the blood are to be feared and, depending on the drug, can have considerable effects on the patient. Frequently affected by an interaction with St. John’s wort are, in addition to the (contraceptive) pill, various AIDS drugs (e.g. HIV protease inhibitors). Many can also be massively influenced by taking St. John’s wort at the same time.

When St. John’s wort is combined with various immunosuppressive drugs, a rejection of a transplant is to be feared. For this reason, the treating physician must always be informed about other medications before taking St. John’s wort. Depending on the patient, it may be necessary to discontinue or change a medication.

Antibiotics,
Cardiac glycosides,
Blood Thinner
As well as medicines for epilepsy and anxiety disorders (antiepileptic drugs, benzodiazepines)

While taking St. John’s wort, the effect of the contraceptive pill can be reversed. The exact interaction of St. John’s wort and the pill has not yet been fully clarified, but there is a clear increase in the incidence of unwanted pregnancies. This is because St. John’s wort increases the activity of various enzymes (cytochrome P450 monooxygenases) in the liver.

These enzymes are also involved in the metabolism of the pill. As a result, the pill is broken down more quickly and cannot fully unfold its hormonal effect. There is a significantly increased risk of unwanted pregnancies.

These interactions of St. John’s wort and the pill depend on the dosage of St. John’s wort. Low-dose applications in the form of tea or St. John’s wort oil do not have any consequences for the effectiveness of the pill. Studies have shown that even with drug therapy with a daily dose of less than 900 mg, there is no effect on the contraceptive pill.

Nevertheless, before taking St. John’s wort regularly, you should always consult your (gynecologist) doctor or pharmacist. An interaction between St. John’s wort and alcohol has not been established to date. The experience gathered over many years about possible side effects and interactions during a therapy with St. John’s wort could not show any signs of an effect of alcohol consumption.

This is due to the fact that St. John’s wort and alcohol are metabolised independently of each other in the liver. While St. John’s wort increases the activity of the so-called cytochrome P450 monooxygenases, which are responsible, among other things, for the activation and breakdown of drugs, alcohol is metabolized by other specific enzymes (alcohol dehydrogenase, aldehyde dehydrogenase). No consequences for the liver are to be feared. On the contrary, the effect of St. John’s wort stimulates the metabolism of the liver.