Course Content
Introduction
Dietary supplements are commonly used by people throughout North America and around the world to improve general health, prevent health problems, and to relieve symptoms of some medical conditions. Dietary supplements may be used as an alternative to conventional medical care (alternative medicine) or in addition to conventional medical care (complementary medicine). There are nearly 1500 documented interactions between drugs, herbal medicines, and dietary supplements. These interactions can cause a wide variety of harmful effects. Taking an herb or supplement could change the way a prescription medicine works in the body, causing symptoms like an overdose or it might cause the medicine not to work at all.
Some medical professionals practice “integrative medicine” which seeks to merge traditional or alternative medical practices with conventional medicine practices. Integrative medicine practitioners may routinely combine the therapeutic use of dietary supplements with conventional therapies.
Common types of dietary supplements include vitamins, minerals, herbs, and other natural ingredients. Dietary supplement products may include a single ingredient or multiple ingredients. Ingredients may also include a combination of vitamins, minerals, herbs, and other natural ingredients. Although most supplement ingredients lack rigorous evidence of health benefits in humans, many ingredients do have evidence of certain pharmacological effects. When supplements are combined with conventional drugs, there is the potential for drug-supplement interactions. These interactions may be pharmacodynamic or pharmacokinetic.
What’s a dietary supplement?
The term “dietary supplement” refers to a specific class of regulated products. Dietary supplements are a unique class of products, distinct from foods, prescription drugs, and over-the-counter drugs. Although distinctly regulated, all of these product categories are regulated in the United States by the Food and Drug Administration (FDA). Dietary supplements are defined by the Federal Food, Drug, and Cosmetic Act as follows:
Dietary supplements include dietary ingredients such as a vitamins, minerals, herbs or other botanicals, amino acids, or dietary substances for use by man to supplement the diet by increasing the total dietary intake; or a concentrate, metabolite, constituent, extract, or combination of the preceding substances.
Dietary supplements may be in the form of tablets, capsules, softgels, gelcaps, powders, and liquids.
Dietary supplements may NOT include other regulated products such as:
Foods
Medical foods
Over-the-counter drugs
Prescription drugs
Homeopathic products
Cosmetics
Each of these products falls into a unique regulatory category with its own set of rules and regulations.
Regulation of Dietary Supplements
It is common to hear health care consumers and health professionals proclaim that supplements are “unregulated.” This is a common mistake or misunderstanding. Dietary supplements are in fact regulated by the Food and Drug Administration; however, the regulations governing dietary supplements are much different than prescription drug regulation.
From a regulatory standpoint, dietary supplements are intended to be used much differently than prescription drugs. While prescription drugs are primarily intended to treat specific medical conditions, dietary supplements are only intended to supplement or add to the nutrients in the diet.
In reality, while many people take supplements to simply to enhance intake of certain dietary nutrients (e.g., a multiple vitamin), many people also take supplements to prevent or treat medical conditions. For example, St. John’s wort and S-adenosyl-L-methionine (SAMe) are commonly used for treating symptoms of depression; glucosamine is used for relieving symptoms of osteoarthritis; coenzyme Q10 is used to prevent statin-related myopathy and to prevent migraine headaches. Clearly, there is a mismatch between regulatory intent and how dietary supplements are actually used.
In the United States, dietary supplement products are regulated through the Dietary Supplement Health and Education Act (DSHEA) of 1994. These regulations are in striking contrast to those governing prescription drugs. Prescription drugs must undergo a rigorous premarketing approval process that requires extensive scientific study and clinical trials. For dietary supplements, premarketing approval is not required.
* Safety does not need to be proven before marketing; however, products with evidence of harm may be removed from the market. The burden of proof is on the FDA.
** From a regulatory standpoint, supplements are not intended to treat medical conditions, therefore proving “effectiveness” for a medical condition is irrelevant.
*** Although specific manufacturing practices are required, those governing supplements are not as rigorous as those for prescription drugs.
Since dietary supplements are not regulated as products intended to treat medical conditions, supplement products cannot make “medical claims” to treat or prevent or cure disease.
Supplement manufacturers are only permitted to make general “structure or function” claims. Examples of these claims include:
Supports healthy circulation
Promotes metabolism
Builds strong bones
These claims are often based the suspected role or function of a particular nutrient in the body or may be based on traditional usage.
Structure or function claims are not necessarily based on any scientific evidence.
Prevalence of Dietary Supplement Usage
When the Dietary Supplement Health and Education Act (DSHEA) was passed in 1994, the use of dietary supplements skyrocketed in the United States. Supplement sales continue to grow by 5% to 8% per year. By 2020, sales are estimated to reach over $55 billion.
Source: Nutrition Business Journal
Most recent comprehensive data on dietary supplement usage in the United States from 2012 survey.
Dietary supplements are the most commonly used form of alternative medicine.
In the general population, dietary supplement (not including vitamins and minerals) usage rates were close to 18% in 2012.
According to another survey, the National Health and Nutrition Examination Survey (NHANES) from 2005-2008, the rate of dietary supplement usage (including vitamins and minerals) was about 50%. This rate increased to about 60% in those with a diagnosed medical condition.
Predictors of Dietary Supplement Use
Dietary Supplement Usage with Rx Drugs
Many people take dietary supplements and drugs together. Those who combine dietary supplements and prescription drugs have a higher risk of potential drug-supplement interactions. According to NHANES, about 50% of those with a medical condition take a supplement and prescription drug together. This number increases to 70% in those with osteoporosis and 60% in those with cancer.
Survey data also show that there is a higher rate of combined supplement and prescription drug use in certain groups, including:
those who use multiple dietary supplements or multiple drugs.
those who are over the age of 60 years.
Who’s at Risk for Drug-supplement Interactions?
Patients at risk for drug-supplement interactions are those who are most likely to take drugs and supplements together.
Those patients with the greatest risk of experiencing a drug-supplement interaction are those who combine a greater number of supplements and drugs.
As drug and supplement combinations increase, the interaction potential grows exponentially.
Patients who are more likely to take an increased number of supplements and drugs are those who are elderly or female gender or who have a chronic medical condition.
Several surveys have evaluated the risk of potential drug-supplement interactions in certain specific populations. These surveys typically assess the supplements and drugs taken at the patient or population level and then assess whether there is a potential interaction between those products based on current evidence. Typically, these surveys do not assess actual interactions, but they only assess the potential for interactions to occur. Based on these data (see following slide), the highest risk is in primary care, oncology and senior populations. There is a lack of reliable data evaluating the actual risk of clinically significant drug-supplement interactions.
Surveys of the Potential for Drug-supplement
Interactions in Specific Populations
Risk Factors for MAJOR Interactions
Not all drug-supplement interactions are clinically meaningful; however several factors can make certain interactions between drugs and supplements a major clinical concern. These factors include individual patient characteristics, the specific supplements taken, and the potential adverse outcome.
Certain patient groups may be more likely to experience a major interaction due to frailty or because of the medications they are taking.
Certain supplements may also predispose to major interactions due to potential pharmacological effects or effects on certain drug-metabolizing enzymes.
Those interactions resulting in certain events, such as bleeding, may also be more likely to be clinically meaningful and severe.
Types of Drug-Supplement Interactions
Like drug-drug interactions, there are two categories of drug-supplement interactions. These include pharmacodynamic interactions and pharmacokinetic interactions.
Pharmacodynamic interactions are those interactions where additive or oppositional pharmacological effects change the action of drugs. An example of a pharmacodynamic interaction is when two substances are taken that both increase serotonin levels in the brain. The combination of the two substances results in additive effects and increased serotoninergic adverse effects. Another example of a pharmacodynamic interaction is when warfarin is taken with vitamin K. Warfarin inhibits vitamin K-related blood clotting. Taking vitamin K therefore decreases warfarin-related anticoagulation potentially resulting in therapeutic failure.
Pharmacokinetic interactions involve absorption, distribution, metabolism, or elimination (ADME) of drugs. These interactions most commonly involve inhibition or induction of cytochrome P450 drug metabolizing enzymes such as CYP3A4, CYP2D6, CYP2C9, CYP2C19 and others. Pharmacokinetic interactions may also involved inhibition or enhancement of drug absorption in the gut or affects on drug transport proteins such as P-glycoprotein (PGP) or organic anion transporting polypeptides (OATP).
Pharmacodynamic Interactions
Pharmacodynamic interactions can often be predicted if you know something about the pharmacology of a given supplement ingredient. For example, if you know that a supplement ingredient has antiplatelet or anticoagulant effects, then you can deduce that it may interact and have additive effects when combined with antiplatelet or anticoagulant drugs such as warfarin, clopidogrel, aspirin, and others.
Most pharmacodynamic interactions are not documented in studies and, therefore, in many cases these interactions will not be detected by electronic interaction screening programs. As a result, most pharmacodynamic interactions are theoretical in nature, based primarily on evidence (often in vitro or animal model) of pharmacological effects alone.
One of the best ways to detect potential pharmacodynamic interactions is to watch for patients who take supplements for a medical condition for which they are also taking prescription drugs. In many cases, dietary supplements used for a particular medical condition have pharmacological effects similar to the prescription drugs used for the same condition. For example, dietary supplements used for diabetes often have hypoglycemic effects which may result in hypoglycemic events when combined with prescription drugs that are used for diabetes.
Pharmacodynamic interactions are often managed by stopping the dietary supplement or reducing the dose of the supplement or prescription drug.
Anticoagulant / Antiplatelet Drugs:
Several supplements have the potential to cause a pharmacodynamic interaction with anticoagulant and antiplatelet drugs.
Most of these potential interactions are due to evidence of antiplatelet effects of the supplement ingredient.
Combining these supplements with anticoagulant or antiplatelet drugs may increase the risk of bruising and bleeding events.
Examples of supplements that may interact with anticoagulant or antiplatelet drugs include:
Examples of supplements that may interact with anticoagulant or antiplatelet drugs include: cont.
Hypoglycemic drugs
Several supplements commonly used for diabetes have hypoglycemic effects.
When combined with conventional diabetes drugs, these supplements may increase the risk of hypoglycemia.
Examples of these dietary supplements include:
Sedative drugs
Some dietary supplements have sedative effects and are used for relaxation and to improve sleep.
These supplements may increase the risk of excessive sedation when combined with sedative drugs.
Examples of these dietary supplements include:
Serotonergic drugs
Some supplements, especially those used for neuropsychiatric conditions, have serotonergic effects.
Using these supplements with other serotonergic agents may increase the risk of serotonergic side effects.
Examples of these dietary supplements include:
Pharmacokinetic Interactions
Unlike pharmacodynamic interactions, pharmacokinetic interactions usually cannot be predicted. Many supplement ingredients have been found to impact drug metabolizing enzymes or drug transport proteins; however, relatively few have been found to alter these enzymes in humans. Research findings in vitro or in animals often does not translate into clinically significant interactions in humans.
The clinical significance of pharmacokinetic interactions can vary substantially from patient-to-patient. Similarly, product formulation variability can also impact the clinical significance of pharmacokinetic interactions.
Different extracts of the same botanical ingredient can impact the phytochemical profile and result in variable effects on drug metabolizing enzymes. For example, some formulations of garlic with higher levels of the constituent allicin have been found to induce the CYP3A4 drug metabolizing enzymes. Other formulations of garlic with low levels of allicin have not been found to induce CYP3A4.
Over 100 dietary supplement ingredients have been found to potentially impact a cytochrome P450 enzyme or drug transport protein. The chart below provides the number of supplement ingredients identified to potentially affect specific drug metabolizing enzymes or drug transport proteins. In most cases, evidence is based on in vitro or animal model research. It is often unclear if effects found in vitro or animal models will translate to a clinically meaningful interaction in humans.
Pharmacokinetic Interactions: St. John’s wort
St. John’s wort is one of the first herbal supplements found to cause significant drug interactions. In 2000, researchers at the National Institutes of Health found that St. John’s wort reduced levels of the HIV drug indinavir by 57% through induction of the CYP3A4 enzyme. Since then, numerous additional studies have found that St. John’s wort substantially reduces levels of many other drugs. St. John’s wort has also been shown to induce the drug transport protein P-glycoprotein which is responsible for transporting drugs across cell membranes.
Some examples of other drugs that have been shown to be reduced by St. John’s wort include:
↓ ethinyl estradiol by 13% to 15%; advise women to use alternate form of contraception if they take St. John’s wort.
↓ cyclosporine by 30% to 70%
↓ imatinib by 30%
↓ irinotecan by 50%
↓ digoxin by 25%
↓ methadone by 47%
↓ omeprazole by up to 50%
Since St. John’s wort induces CYP3A4 and P-glycoprotein it has the potential to affect levels of many other drugs. The metabolism of over 50% of all drugs available may be affected by this enzyme. Reduced drug levels may result in treatment failure.
Clopidogrel is an interesting exception since it is a prodrug. St. John’s wort increases clopidogrel’s conversion to its active metabolite and increases its effects.
Patients taking substrates of CYP3A4 should be advised to avoid St. John’s wort.
Pharmacokinetic Interactions: Goldenseal
Goldenseal is commonly used in “immune support” supplements, often in combination with other ingredients such as echinacea or vitamin C. Goldenseal inhibits the drug metabolizing enzymes CYP3A4 and CYP2D6. It may also inhibit P-glycoprotein.
Studies have found that goldenseal may significantly increase levels of several drugs, including:
↑ cyclosporine levels by 35%
↑ midazolam levels by 64%
↑ digoxin peak levels by 14%
Goldenseal may also increase levels of other substrates of CYP3A4 and CYP2D6. This may lead to increased drug effects and side effects. Goldenseal should be used cautiously or avoided in patients who are taking drugs metabolized by these enzymes.
Pharmacokinetic Interactions: Black seed
Black seed is a middle eastern supplement ingredient commonly used for allergies, diabetes, high blood pressure, and many other conditions. Black seed inhibits CYP3A4 and CYP2D6 drug metabolizing enzymes.
Research in humans shows that it significantly increases levels of dextropmethorphan. Black seen may also increase levels of other drugs that are substrates of these enzymes. This may lead to increased drug effects and side effects.
Advise patients taking substrates of these enzymes to avoid or use black seed-containing supplements cautiously.
Pharmacokinetic Interactions: Schisandra
Schisandra is a common supplement ingredient in traditional Chinese medicine. It has been found to be a strong inhibitor of CYP3A4.
In human studies it has been found to significantly increase levels of tacrolimus by up to 212%. It has also been shown to increase levels of midazolam by 119%. Schisandra may also significantly increase levels of other drugs metabolized by CYP3A4 and increase the risk of serious side effects.
Patients taking substrates of CYP3A4 should avoid taking schisandra.
Pharmacokinetic Interactions: Turmeric
Turmeric is a spice that is also commonly found in supplements used for joint pain and inflammation. Turmeric inhibits the drug metabolizing enzyme CYP2D6.
In human research, it has been shown to increase levels of dextromethorphan. Turmeric may also increase levels of other drugs that are substrates of these enzymes. This may lead to increased drug effects and side effects.
Advise patients taking substrates of these enzymes to avoid or use turmeric-containing supplements cautiously.
Pharmacokinetic Interactions: Other Supplement Ingredients
Several other dietary supplement ingredients have been found to potentially alter metabolizing enzymes; however, in many cases these data are based on in vitro or animal model data and there may be some conflicting evidence. Therefore, it is not yet clear whether these dietary supplement ingredients cause clinically meaningful effects on these enzymes.
Examples of Other Supplement Ingredients that may Impact Drug Metabolizing Enzymes
Narrow Therapeutic Index Drugs
Dietary supplements with the potential to cause interactions should be used with extra caution in patients who take narrow therapeutic index drugs. This is because small changes in systematic drug levels of narrow therapeutic index drugs can cause significant harm. Increased levels can result in serious adverse side effects. Decreased levels can result treatment failure or inadequate response.
Examples of narrow therapeutic index drugs include:
5-Fluorouracil
Aminoglycosides
Levothyroxine
Carbamazepine
Cyclosporine / Tacrolimus
Digoxin
Lithium
Phenytoin
Warfarin
Zidovudine
Several dietary supplement ingredients have been found to impact narrow therapeutic index drugs.
5-Fluorouracil (5-FU)
Green tea (animal model) increased levels of by 425%
LevothyroxineCalcium decreases absorption of levothyroxine by 20% to 25%
Chromium decreases absorption by about 17%.
Levothyroxine should be taken with a plain glass of water; should be taken at least 30 minutes before supplements or multiple vitamins.
Carbamazepine
Caffeine decreases absorption by 32%; loss of therapeutic effects.
Pomegranate increases levels by 150% in animal model.
Cyclosporine / Tacrolimus
St. John’s wort, goldenseal, schisandra, quercetin shown to increase levels.
WarfarinVitamin K or vitamin K-containing supplements (e.g., stinging nettle, alfalfa, parsley, other) can decrease warfarin effectiveness.
Coenzyme Q10 and St. John’s wort may also reduce warfarin effects.
Many other supplements with antiplatelet effects may increase the risk of bleeding in patients taking warfarin.
Interaction Risks in Specific Patient Populations
The following section reviews potential effects of dietary supplements in patients taking anticoagulants, cardiovascular medications, psychiatric medications, laxatives, diabetes medications, or medications for human immunodeficiency virus (HIV) infection.
Patients Receiving Anticoagulants:
Case reports have shown interactions between the anticoagulant warfarin (Coumadin) and St. John’s wort, ginkgo, garlic, and ginseng. Studies have demonstrated that St. John’s wort increases the metabolism of warfarin, leading to diminished serum levels. However, the clinical response to the combination has not been quantified.
Ginkgo does not interact with warfarin or aspirin directly, but has demonstrated antiplatelet activity. In combination with nonsteroidal anti-inflammatory drugs, especially aspirin, ginkgo has been reported to cause severe bleeding, including intracranial bleeding.
Garlic has intrinsic antiplatelet activity. However, one clinical trial has demonstrated that garlic is safe and poses no serious hemorrhagic risk for monitored patients taking warfarin.
A low-quality clinical study found no effect of Asian ginseng (Panax ginseng) in combination with warfarin. American ginseng (Panax quinquefolius), a separate plant, decreases warfarin serum levels in humans, resulting in less anticoagulation.
Eleuthero (Eleutherococcus senticosus) has not been studied; however, it contains a constituent that inhibits platelet aggregation.
Vitamin E and fish oil are often mentioned in reviews of supplement-drug interactions. In a clinical study of 16 patients, fish oil (3 to 6 g daily) did not affect coagulation status in patients receiving warfarin.
Vitamin E may have an effect on bleeding time. In vitro studies demonstrate potentiation of the antiplatelet effect of aspirin by vitamin E. However, clinical trials with and without warfarin and vitamin E show no increased risk of bleeding even though high doses of vitamin E may antagonize vitamin K.
Cranberry juice, although implicated in case reports, has not been shown to affect coagulation in a controlled study.
Given the narrow therapeutic index of warfarin and the serious consequences associated with small changes, the anticoagulation status in patients taking dietary supplements should be carefully monitored whenever they initiate or stop taking any supplement, or when a new bottle of the same product is used, until the effect in the individual patient is known. Specifically, patients receiving American ginseng should be monitored when changing products or even bottles of the same product.
Patients Receiving Cardiovascular Medications:
Of all the supplements used by patients who have cardiac disease, St. John’s wort, used to treat mood disorders, is associated with the most interactions. It decreases serum levels of verapamil (Calan) and statins. Blood pressure and lipid levels, respectively, should be monitored closely if a patient is taking one of these drugs and St. John’s wort.
The suspected mechanisms of St. John’s wort interactions are by the induction of cytochrome P450 (CYP450) isoenzymes CYP3A4, CYP2C9, and CYP1A2, and the transport protein P-glycoprotein, leading to decreased concentration of medications. In one study, St. John’s wort decreased digoxin blood levels by 25 percent, most likely by inducing the P-glycoprotein, which decreases the bioavailability of digoxin. Ginseng is another commonly used herb that has been reported to cause an increase in digoxin serum levels in a case report of one patient. Digoxin levels should be monitored in patients taking eleuthero or St. John’s wort.
Patients Receiving Psychiatric Medications:
Although it probably is not its inherent mechanism of action in the treatment of depression, St. John’s wort may have an effect on serotonin levels. It has been associated with serotonin syndrome in patients also receiving a selective serotonin reuptake inhibitor (SSRI). St. John’s wort should be tapered off when an SSRI is initiated. Patients should be cautioned not to initiate St. John’s wort when receiving these drugs.
St. John’s wort decreases serum levels of psychiatric medications metabolized by the CYP450 enzyme system. It has been shown to affect serum levels of benzodiazepines and tricyclic antidepressants, although these changes may not result in a clinical effect.
Patients Taking Bulk Laxatives:
Psyllium and related bulk-forming laxatives are dietary supplements often not considered to be medications by many patients. However, they can slow or diminish absorption of many drugs. Psyllium can reduce carbamazepine (Tegretol) absorption and serum levels. Additionally, there is a case report showing that psyllium decreased the absorption of lithium. As a general rule, bulk laxatives such as psyllium should not be taken at the same time as other medications; their use should be separated by several hours to allow absorption to occur.
Patients Receiving Diabetes Medications:
Supplement-drug interactions are not well documented in patients being treated for diabetes. However, a number of supplements have intrinsic effects on serum glucose. Ginseng has hypoglycemic activity in patients with diabetes, and this effect might be additive in patients taking oral hypoglycemics or insulin. Chromium and psyllium also have hypoglycemic effects. The effect of these supplements is unpredictable in individuals, and no specific changes in hypoglycemic doses are needed unless blood glucose changes occur.
Patients Receiving HIV Medications:
Most antiretrovirals are metabolized via the CYP3A4 and P-glycoprotein systems. Dietary supplements that induce these systems may decrease serum levels of the antiretrovirals. St. John’s wort is the dietary supplement with the most evidence of an effect on these systems. Limited clinical research has demonstrated reductions in antiretroviral serum concentrations in patients taking garlic and vitamin C. Milk thistle, Echinacea species, and goldenseal inhibit CYP450 enzymes in vitro, but not to a clinically relevant effect. The effectiveness of HIV therapy should be monitored in patients taking these supplements, particularly St. John’s wort. Because of the risk of a dangerous interaction, patients taking antiretrovirals should be discouraged from using St. John’s wort.
General Considerations with Dietary Supplements:
Pharmacists should advise patients about the safety and effectiveness of the products they are using or are considering using. Most patients do not realize the great variability among dietary supplements. Several groups have set up standards for production, bioavailability, and purity of dietary supplements, including the United States Pharmacopeia Convention, Consumer Labs, and the NSF International.
Products approved by any of these organizations will be marked with their seal.
Two out of three patients taking prescription medications and supplements do not tell their physician about their dietary supplement use, perhaps because they do not consider supplements to be legitimate drugs or to carry risks. Therefore, all patients should be asked about their use of dietary supplements. Rather than closed, yes or no questions, physicians should ask, “What vitamins, herbs, and other supplements do you use? What about teas, tinctures, or natural products?” These supplements should be treated as other drugs and recorded in the patient record.
How to Reduce Interaction Risk
The patients who have the greatest risk of experiencing a drug-supplement interaction are those who take multiple dietary supplements and multiple drugs concomitantly. Generally speaking, these patients typically include older adults and those who have chronic conditions. Most of these patients never discuss their use of dietary supplements with their healthcare providers. Many patients believe that dietary supplements are beneficial and completely harmless. Most patients are not aware that many dietary supplements have the potential to interact with the medications that they are taking.
In some cases, patients do not talk to their healthcare providers about supplements because they believe their providers are not knowledgeable about supplements. They may also fear negative feedback or that their providers will be critical or judgmental about their use of dietary supplements. Therefore, the best first step that can be taken to help reduce the risk of drug-supplement interactions is to ask each patient specific questions about their use of dietary supplements. This should be done in a non-critical and non-judgmental way in order to facilitate open and honest communication and full disclosure about supplement use.
Once information is obtained about dietary supplement use, a screening can be done in order to detect potential drug-supplement interactions. This screening process can represent a significant challenge for healthcare professionals for multiple reasons, such as:
Inadequate reference resources available to conduct a reliable screening for interactions.
Inadequate personal knowledge and insight about dietary supplement pharmacology.
Inadequate information about the ingredients contained in dietary supplement products.
Lack of time available to thoroughly evaluate interaction issues.
If help is needed to evaluate potential drug-supplement interactions, consider pursuing one or more of the following resources:
Consult with a knowledgeable colleague.
Contact a drug information center.
Purchase a reliable resource (e.g., Natural Medicines) that can facilitate screening of drug-supplement interactions.
Summary
The pharmacist, along with the prescriber has a duty to ensure that patients are aware of the risk of side effects and a suitable course of action should they occur. With their detailed knowledge of medicine, pharmacists have the ability to relate unexpected symptoms experienced by patients to possible adverse effects of their drug therapy. The practice in clinical pharmacy also ensures that adverse drug reactions (ADRs) are minimized by avoiding drugs with potential side effects in susceptible patients. Thus, pharmacist has a major role to play in relation to prevention, detection, and reporting ADRs. Prior to recommending any nutritional supplements or a new medication, health care professionals must evaluate a patient’s medical history and medication profile to screen for potential drug–supplement interactions or contraindications. It is also crucial that patients be made aware of these potential interactions as well as understand the importance of notifying their primary health care provider of all supplements that they are taking, including alternative and complementary products.
Active Learning
The possibility of drug interactions, direct toxicities, and contamination with active pharmaceutical agents are among the safety concerns about dietary and herbal supplements. Although there is a widespread public perception that herbs and botanical products in dietary supplements are safe, research has demonstrated that these products carry the same dangers as other pharmacologically active compounds. Interactions may occur between prescription drugs, over-the-counter drugs, dietary supplements, and even small molecules in food—making it a daunting challenge to identify all interactions that are of clinical concern.
Concerns about herb-drug interactions are often not based on rigorous research. Most herb-drug interactions identified in current sources are hypothetical, inferred from animal studies, cellular assays, or based on other indirect means; however, attention to this issue is needed for drugs with a narrow therapeutic index, such as cancer chemotherapeutic agents, warfarin, and digoxin.
To date, well-designed clinical studies evaluating herbal supplement-drug interactions are limited and sometimes inconclusive.
https://nccih.nih.gov/health/providers/digest/herb-drug
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