Dietary supplements can have serious side effects when mixed with prescription drugs, but not all herb-drug interactions are bad.

By Catherine Ulbricht | July 1, 2012

istockphoto, DNY59


For more than 5,000 years, herbs and other natural ingredients have been used for medicinal purposes. Today, people use such concentrated natural products as supplements to help combat various diseases, from depression to cancer, as well as to boost health, including immunity and memory. Based on Natural Standard research, in the United States alone more than $40 billion is spent each year on these products. An estimated 60 percent of cancer patients try natural products, and 40 percent take vitamins or other dietary supplements.

Just because herbal products are developed from plants, they cannot necessarily be deemed harmless. Like prescription drugs, herbs and supplements may cause unwanted side effects and can interact with prescription drugs, other natural products, or foods, and may even alter diagnostic and laboratory test results. Unlike regulated drugs, however, dietary supplements can be marketed without approval from the US Food and Drug Administration. As a result, herbal products are often not thoroughly evaluated by the FDA unless there is sufficient evidence to prove that they are unsafe. Partly due to this regulatory freedom, as well as to a lack of available clinical research, interactions between herbs and conventional drugs are often overlooked.

In the United States alone more than $40 billion is spent each year on natural products.

Herbs and drugs can interact pharmacodynamically by mechanisms that may be additive, synergistic, or antagonistic. For example, concurrent use of an anticoagulant/antiplatelet drug and natural ingredients that possess antiplatelet activity, such as garlic, may increase the risk of bleeding. Similarly, herbs that lower blood sugar may have additive effects with antidiabetic drugs, thereby increasing the risk of potentially dangerous hypoglycemia (low blood sugar). Some herbs, such as ephedra (ma huang in Chinese), on the other hand, are known to increase blood pressure and may counteract the beneficial effects of antihypertensive medications.

Herbs and medications can also have pharmacokinetic interactions, meaning that the herbs may change the absorption, distribution, metabolism, or excretion of a drug, resulting in altered effects.  Herbs that alter gastrointestinal function, for example, can affect drug absorption, as can those that induce or inhibit metabolic enzymes and transport proteins. Many other herbs have been identified as substrates, inducers, and/or inhibitors of the liver’s cytochrome P450 enzyme system, which is extensively involved in drug metabolism, and can thus affect the clearance of drugs. St. John’s wort, popularly used for the treatment of depression, may reduce levels of antiretroviral agents and immunosuppressants, and can increase the neurotransmitter serotonin, thus making it dangerous to combine with drugs that affect serotonin levels, such as selective serotonin reuptake inhibitor (SSRI) antidepressants.

Many of these interactions could be prevented simply by taking the drug so many hours before or after the supplement, for instance. Furthermore, not all interactions are bad. Thus, combining dietary supplements and prescription drugs should not necessarily be discouraged, but clinicians need to be aware of the potential risks. Indeed, more than 75 percent of doctors and nurses now seek information on complementary and alternative medicine each year, and these numbers are growing. Given this burgeoning interest, it is important to develop and maintain credible resources on herbs and supplements, such as the Natural Standard Research Collaboration, of which I am cofounder. On our website (www.naturalstandard.com), clinicians can access databases and charts guiding appropriate dosage, as well as details about potential concerns. The collaboration also offers continuing medical-education courses dedicated to integrative medicine.

Until health-care providers begin to be more aware of potential drug-herb interactions and begin to utilize the resources available to them to avoid damaging side effects, dietary supplement-drug mixology will remain problematic. 

Catherine Ulbricht is a senior attending pharmacist at Massachusetts General Hospital, and editor-in-chief of both the Journal of Dietary Supplements and Natural Standard. 

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Avatar of: Erica Marini

Erica Marini

Posts: 1

July 3, 2012

Natural Standard really is the best place to go for this information! I work in a pharmacy and their Interactions Checker is so helpful. I rely on it all the time for patient questions.

Avatar of: Carolyn Combs

Carolyn Combs

Posts: 1

July 3, 2012

This article is excellent and speaks to the supreme importance of informing your doctor and pharmacist of all the medications you take, not just the prescription ones. When asked by a health care professional for a list of your medications make sure to include all of the herbs/supplements and other over the counter medications (even if you only take them occasionally). As mentioned above, these medications can have serious drug-drug interactions with your prescription medications. Your doctor or pharmacist can double check for interactions using information found on Natural Standard's website.

Avatar of: RichardPatrock


Posts: 52

July 5, 2012

A nice sales pitch.  I went to the web page for National Standards and was led to a page to supply information that would allow a salesperson contact me.

July 5, 2012

So true! Its really great to see awareness for these drug-supplement interactions being spread. I was shocked to hear that its been suggested that two out of three patients taking prescription medications never mention their use of herbals or dietary supplements to their doctor, even though they're taking prescription drugs at the same time.

July 5, 2012

With such an increasing number of people taking alternative supplements
it is so important that people understand that what they are taking is a drug.
It can have harmful effects on your body that the manufactures may not tell you
or know about. In addition to doing your own research at Natural Standard or
other websites, talking to a health care worker about any new supplement could
save you from serious side effects or interactions. Always better safe than
sorry in matters of your health!

Avatar of: rxman123


Posts: 2

July 6, 2012

Based on the flawed perception that herbals and naturals are
free of side effects appears to be common hope with its users. Taking both
herbs and prescription medications points to real and consistent risks of serious  life threating events.  Let’s not forget the situation with Seldane
and Grapefruit inhibiting the enzymatic conversion of a Seldane metabolite that
caused cardiac arrhythmias and several deaths. 
The information regarding serotonin enhancements with St. Johns wort if
combine with SSRI’s . we must remember that so many of the modern pharmaceuticals
had their genesis from natural products – Aspirin, Ace inhibitors, Cardiac ,
Oncology drugs.  As a society we are led
to believe that potency comes from the pharmaceutical manufacturer. 

Avatar of: Divya Chowdary

Divya Chowdary

Posts: 1

July 6, 2012

It is a common practice in many countries to try an alternative medicine as their first treatment before seeking medical help. This makes it difficult for practitioners to analyze the effects of the herb or supplement with the current regimen. Tools from Natural Standard can help minimize errors and aid practitioners to follow good medical practice.

Avatar of: Hari Behl

Hari Behl

Posts: 1457

July 6, 2012

Admittedly, it is important for the doctor or pharmacist to know what dietary supplements are being taken along with prescription drug. Herbal dietary supplements are relatively safe (as compared to drugs) even if taken along with drugs (mixology as referred to in the article) is a fact that often never boldly accepted. The potency of actives of herbal dietary supplements is never life threatening. It is interesting market where Consumer is convinced because of their traditional use despite resistance from the drug industry or those who have a bias tilt to the other side. While cancer cannot be cured by herbs, flu, cold and digestion disorders do not need drugs.  If food cooked with turmeric, black pepper, basil, garlic and ginger is safe to be taken along with drugs, how can all DS be blamed for threatening life! Consumers need to be educated not threatened.

Avatar of: Melissa Nguyen

Melissa Nguyen

Posts: 2

July 10, 2012

Health care providers should ALWAYS inquire about non-prescription medications when taking patient histories, and give examples of some herbal medications that a patient may neglect to mention, ie. ginseng and garlic. Because some of these herbal remedies are commonly used in various cuisines, patients may not perceive them dangerous.

Avatar of: Melissa Nguyen

Melissa Nguyen

Posts: 2

July 10, 2012

The Natural Standard is a great tool for health care providers and students to access information that was thoroughly analyzed and compiled in monographs and charts. Yes, you do need a subscription to access the site, but you would also need subscriptions to access many medical journals and other medical databases and tools (ie. pubmed, lexicomp, and micromedex). Information on integrative medicine is very diverse and conflicting in general, however the Natural Standard compiles everything nicely in concise monographs and charts for easy reference.

Avatar of: jgonzo220


Posts: 2

July 12, 2012

It's so important for a health care provider to inquire about dietary supplement use. So often when asked the question "what medications are you currently taking?", patients don't think to mention the ginkgo they take for their memory or the SJW for their low mood. It's up to the provider to specifically ask about herbals and dietary supplements!

Avatar of: Carrie Dickinson

Carrie Dickinson

Posts: 1

July 12, 2012

I agree with Melissa.  It's a dangerous to a patient's health when they consider all herbal products safe.  I think it is scary that a lot of consumers also think that because herbal products are on shelves that they are as regulated as over-the-counter and prescription medications.  Like Hari Behl said, education is key because herbal products do have benefits, but aren't benign.   

Avatar of: Emily Paine

Emily Paine

Posts: 1

July 13, 2012

Integrative care certainly seems like the only way forward for the best patient outcomes possible. Care needs to be better coordinated across all healthcare providers to allow for patients to safely take CAM. Patients also need to be aware of the herbs and supplements that are effective for their conditions, and understand the interactions that may exist with their prescription medications. Natural Standard promotes all of these components by publishing evidence-based research relevant to all stakeholders.

Avatar of: Sac


Posts: 1

February 1, 2013

I think it is very important for patients to communicate with their healthcare providers, including pharmacists about any over the counter medication or herbal supplement they are taking.  Your healthcare provider might not know off the top of their head exactly what herb or supplement you are taking and whether it interacts with your medications but luckily we have the resources like Natural Standard to help us evaluate your drug profile and find any potential interactions.  A good tip is to keep a note card in your wallet that has a list of all of the medications you take with the dose and directions.

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