Taking medication and taking herbal remedies at the same time could hide dangers. The interaction between these two categories of substances could give rise to adverse reactions to the drugs themselves. According to a recent research published in The British Journal of Clinical Pharmacology and carried out by researchers at the University of Stellenbosch (South Africa), several natural products could compromise the properties of prescribed drugs by altering their efficacy. We talk about this topic with Dr. Maria Fazio, Head of the Pharmacy at Humanitas.
Cardiovascular diseases and cancer
The authors of the study reviewed the literature available on the subject by selecting forty-nine case reports, where clinical histories of one or more patients are documented, and two observational studies. In total, fifteen cases of adverse drug reactions were detected. One third of patients had cardiovascular disease, more than 22% had been affected by cancer and 16% had received a kidney transplant. These were being treated with drugs such as warfarin (an anticoagulant), alkylating agents (antitumor) or with antirejection drugs, against the possible reactions of an organ transplant, such as cyclosporine.
Researchers found that in patients taking warfarin and/or statins for the treatment of cardiovascular complications, interactions with herbal products such as sage, linseed, St. John’s Grass, goji juice, green tea and chamomile were detected. The metabolism of the anticoagulant drug is mainly mediated by an enzyme (CYP2C9); as the authors of the study report, natural products that alter the activity of this molecule may reduce the action of the drug or lead to bleeding.
Investigator-reviewed studies have documented cases of therapeutic failures and drug toxicity in patients taking antirejection drugs along with natural products such as turmeric and chamomile. The review also found interactions between medicines and natural remedies in patients with depression and convulsive syndromes.
No to DIY
What could cause interaction between medicines and natural products? The drug-natural products interaction can take place at different levels – explains Dr. Fazio – but certainly an important role is attributed to the metabolism of drugs and cytochrome P450 (abbreviated as CYP, P450 and, less frequently, CYP450) and its isoenzymes. The P450 cytochrome family is the body’s main detoxification mechanism for drugs.
Many drugs may have an inductive or inhibiting effect on the activity of one or more isoforms of cytochrome P450, and these phenomena are at the root, in most cases, of the compromising effects on therapeutic action and toxicity effects resulting from the simultaneous intake of different active ingredients, i.e. medicines and even herbs,” the specialist points out.
Patients should not act independently: “The advice we can give is not to rely on DIY but to always involve the doctor or pharmacist; often these are remedies that are bought without prescription or at the supermarket. It is also important that any possible harmful interaction is reported in order to avoid it and it wouldn’t be repeated in other subjects”.
In contrast to the examples given above, herbal drug interactions are now well documented; however, in most cases the clinical consequences of these associations are still unclear: it is certainly useful that patients who associate natural remedies with drugs must declare it. In fact, any herbal remedy containing pharmacologically active substances is actually a drug, as evidenced by the fact that most of the drugs currently on the market are herbal derived,” concludes Dr. Fazio.