The possible risks related to the consumption of natural products capable of causing adverse reactions are now described. The risks are related to the plant, the product and the patient.
Plant-specific adverse reactions can develop due to contamination, presence of toxic substances or phytocomplexes, and variability of harvest times. Adverse reactions caused by the product can be caused by episodes of sophistication, by the variability of titration and by the presence of inadequate information on the label.
Pyrrolizidine alkaloids are contained in Orchidiaceae, Boraginaceae, Asteraceae And Fabaceae. On the fetus these alkaloids have a strong mutagenic power and the toxicity is above all chronic, deriving from the daily consumption of contaminated flour, honey or milk. These alkaloids can cause the "Jamaican mal" which is a severe and lethal form of cirrhosis. Jamaican mal is also known as veno-occlusive liver disease.
Contraindications to herbal medicines: many herbal medicines have contraindications that can cause disorders. We must dispel the legend that natural products are good by definition. Preconceptions do not constitute science (even if science sometimes expresses itself with preconceptions).
The best known examples are:
- the devil's claw causes nausea and / or irritates the gastric mucosa;
- hypericum causes photosensitization;
- ephedra causes hypertension;
- irritates the renal parenchyma;
- pyrrolizidine alkaloids cause hepatotoxicity and teratogenesis,
- anthraquinones, in high doses and for prolonged use, cause melanosis and irritation of the intestinal mucosa.
in relation to the type of action there may be specific contraindications:
- sweet clover, sedative, but also anticoagulant: it should not be used in individuals with coagulation defects;
- and other tonic drugs: they can cause increased anxiety in anxious people;
- hypotensive: they should not be used by individuals who are already hypotheses;
- hypoglycemic agents: they should not be used by people with blood sugar imbalances;
- diuretic herbal teas used for a long time, as adjuvants to the slimming regime: they can cause electrolyte disturbances.
The interactions between herbal medicines and conventional drugs can be:
- synergistic (agonist, summation): eg. aspirin and garlic mother tinctures, both with anticoagulant activity;
- antagonists: eg. the simultaneous intake of conventional anxiolytics and ginseng or guarana;
- indirect: eg. volumetric drugs that increase fecal mass at the same time as drugs for intestinal intake due to the sequestering action of the fibers;
- complementary: eg. an analgesic drug for a slight headache with a light phytotherapeutic sedative to reduce the anxiety component caused by the attack. Or combine an antipyretic drug eg paracetamol, which has no anti-inflammatory action, with a phytotherapeutic anti-inflammatory;
- "": the association of the phytotherapeutic to the synthetic medicine helps to reduce the side effects of the synthetic medicine: this point is of great importance for the future.
INTERACTION BETWEEN VEGETABLE DRUGS AND COMMON USE DRUGS
Many products of plant origin can interact with classic drugs, altering their effects. The interactions that can arise between herbal medicines and drugs are:
- Pharmacokinetic interactions, with consequent modification of the absorption, distribution, metabolism and elimination of the drug. In short, the bioavailability of the drug is modified;
- Pharmacodynamic interactions with consequent modification of the mechanism of action of the drug;
- Chemical interactions concerning the pharmaceutical phase.
THE PHARMACOKINETIC INTERACTIONS
INTERFERENCE IN THE ABSORPTION PHASE
At the level of absorption, the natural product can create interference with the drug .:
- It can bind to the drug forming an insoluble complex in gastrointestinal fluids, preventing its absorption;
- It can absorb the drug preventing its absorption;
- It can change the gastric pH;
- It can speed up or slow down intestinal motility;
- It can modulate P-glycoprotein (P-gp).
P-glycoprotein is an ATP-dependent transporter protein, used by the cell as a sort of defense to reduce absorption or accentuate the elimination of endogenous or exogenous toxins. This glycoprotein is found in the kidney, intestine, BEE and pancreas. P-gp has substrates to which not only toxins bind, but also drugs such as anticancer, cardiovascular, antibiotics, steroids, cytokines, antihistamines , anti-HIV, anesthetics etc.
If the natural product modulating P-gp is taken at the same time as the previously mentioned drugs, there is a modification of the activity of this glycoprotein, which in turn modifies the absorption of the drugs with a consequent alteration of the pharmacological activity. For example, grapefruit juice acts on P-glycoprotein, modifying the bioavailability of the drug administered, increasing its absorption and reducing its elimination. St. John's wort also acts on this transport protein by increasing the elimination of the active ingredient. Other natural products able to modify the bioavailability of a medicine are hawthorn, cardamom, garlic and milk thistle, in similar ways to those seen for St. John's wort.
INTERFERENCE IN THE METABOLISM PHASE
Metabolism is the pharmacokinetic process most "affected" by the interactions between herbal medicines and drugs. The phases of metabolism involved are phase 1 and phase 2 reactions, with a greater induction - by plant products - of cytochromes P450.
Thanks to the induction of cytochrome P450 there is a decrease in the efficacy of the drug, due to its accentuated metabolism. Conversely, the slowing down of the functionality of cytochrome P450 prolongs the permanence of the drug in the body; therefore, there will be an increase in the efficacy of the drug. Among the substances that interfere with the metabolism of drugs we once again mention garlic and St. John's wort.
INTERFERENCE IN THE ELIMINATION PHASE
The elimination of the drug can be influenced by natural products that act as diuretics (increase the production of urine), by urine acidifiers (increase the excretion of basic drugs) or by inducers of P-glycoproteins present in the kidney (increase the excretion of the substrates that bind to these P-gp).
THE PHARMACODYNAMIC INTERACTIONS
As far as pharmacodynamic interactions are concerned, the natural product increases or reduces the activity of a drug. The following table shows some examples of interactions between herbal medicines and drugs, with the possible effects that can be obtained.
NATURAL PRODUCT
In addition to harpagophytum and blueberry, Ginko, Hypericum, Garlic and Gingseng can interact with various drugs. Ginko reacts mainly with Warfarin, calcium antagonists, antidepressants and salicylates. Hypericum with Warfarin, digoxin, anxiolytic antidepressants, sex hormones, antivirals, immunosuppressants, anticancer, anesthetics and theophylline. Garlic with Warfarin, ACE inhibitors, antivirals and anti-inflammatories. Finally, Gingseng interacts with Warfarin, antiplatelet, antidepressant and antiepiletics.
Ginko is now examined with its possible interactions and effects.
- Ginko + Warfarin = antagonizes the platelet aggregation factor (PAF) with consequent haemorrhage;
- Ginko + anti-inflammatory = antagonizes the PAF;
- Ginko + antiplatelet drugs = antagonizes the PAF;
- Ginko + calcium antagonists = induction of cytochrome P450 with consequent hypotensive action;
- Ginko + antidepressant = GABAergic action with CNS depression up to coma.
It is very important to mention some precautions.
- Natural is certainly not synonymous with harmless, on the contrary, if anything it is the opposite, because natural products are subject to fewer controls;
- Attention to possible interactions between natural products and drugs;
- Avoid the consumption of natural products in case of pregnancy and breastfeeding;
- Avoid administration to the elderly, children and infants;
- In case of adverse reactions, immediately report them to the competent bodies by filling in the appropriate forms;
- ALWAYS consult your doctor before combining herbal medicines with synthetic drugs.
In conclusion, it is considered important to underline that:
- considering the extreme variety of substances contained in herbal medicines, the possible points of interaction between drugs and herbs are manifold, with even unexpected final biological effects. For example, in a 2011 study conducted on animal models, ginkgo reduced (and not amplified as is commonly believed) the antiplatelet effects of warfarin (since it stimulated the hepatic metabolism accelerating its elimination from the body). It should also be considered that many of the much feared interactions between herbs and drugs are actually only theoretical or hypothetical , or true only in experimental models, without clinical relevance. For these reasons and the unpredictability of the responses, however, the warning of extreme caution remains essential if it is necessary to associate a phytotherapic with a drug therapy.
Other articles on "Phytotherapy: the risks of natural"
- Phytovigilance
- Toxicity and toxicology
