Some precautions about herbs

Oct. 1, 1999
While interested in all of the details of each and every herb, most hygienists really want just a concise account of the most common herbs, their efficacy, precautions, and drug interactions. The National Institute of Health (NIH) is currently conducting extensive research on most herbs, but, in the interim, we need to rely on the research that is currently available. Most of the studies have been conducted in Europe and Asia, since that is where herbs are most widely prescribed by physicians.

Cynthia R. Biron, RDH

While interested in all of the details of each and every herb, most hygienists really want just a concise account of the most common herbs, their efficacy, precautions, and drug interactions. The National Institute of Health (NIH) is currently conducting extensive research on most herbs, but, in the interim, we need to rely on the research that is currently available. Most of the studies have been conducted in Europe and Asia, since that is where herbs are most widely prescribed by physicians.

According to the Food and Drug Administration (FDA), herbs are considered food, specifically dietary supplements. The Dietary Supplement Health and Education Act of 1994 permits herbs to be sold as dietary supplements, as long as the labels do not include therapeutic claims. The label may describe the herbs` means of improving bodily function. This act also states that the FDA must prove that an herb is unsafe before removing it from the market.

It is imperative that all health care professionals be knowledgeable about precautions and drug interactions relative to herbs. We cannot possibly store all of the information about herbs in our long-term memories any more than we can store all the information about prescription drugs.

We now have two reliable references that should be alongside the Physician`s Desk Reference (PDR) in every dental office. The two references are: PDR for Herbal Medicines and The Complete German Commis-sion E Monographs: Therapeutic Guide to Herbal Medicines.

Descriptions of some of the more popular herbs on the market follow.


There is more scientific evidence of positive effects from garlic than any other herb on the market today. People take it for a whole host of reasons, including lowering blood pressure, fighting infection, and preventing cancer. The studies show that it does lower cholesterol. Several studies have shown that garlic can reduce total serum cholesterol by 10 percent and triglycerides by 15 percent.

The active ingredient in garlic is allicin. Most of the allicin is destroyed when cooking, so one would need to consume one to four whole cloves of garlic per day for the therapeutic effects. Because allicin also breaks down with stomach acid, garlic supplements that are entericoated and only released in the small intestine are the most effective. The recommended dosage is 2 to 5 mg of pure allicin daily.

Precautions: Some people are allergic to garlic, especially atopic individuals. Garlic may cause heartburn, flatulence, and halitosis.

Drug interactions: Garlic tends to reduce clotting time, therefore patients taking aspirin, other antiplatelet drugs, or anticoagulants should avoid supplemental intake of garlic.


Studies have shown that ginkgo improves circulation and fosters mild to moderate improvement in memory and cognitive function in Alzheimer`s patients. It is also used to improve sexual dysfunction, especially when the cause is due to adverse effects from selective serotonin reuptake inhibitors. The recommended dosage is 60 mg twice daily.

Precautions: Prolonged use of ginkgo has resulted in a few cases of bilateral subdural hematomas. Adverse effects associated with the use of ginkgo are headaches, dizziness, gastrointestinal disturbance, and vertigo.

Drug interactions: Ginkgo could potentiate the action of antiplatelet and anticoagulant drugs.


There is a lack of scientific evidence to support the theories that ginseng builds resistance to stress, boosts energy, acts as an aphrodisiac, or improves circulation in human beings. Most of the valid studies were conducted on animals. The studies conducted on humans have been small and often conflicting.

Nevertheless, sales of ginseng have skyrocketed in the past several years, and individuals frequently claim ginseng improves their well-being in one or more of the aforementioned ways. The recommended dosage is 100 to 300 mg of extract standardized at 7 percent ginsenosides, three times a day.

Precautions: Ginseng acts as a stimulant and, in some individuals, causes nervousness, agitation, headaches, elevated blood pressure, heart palpitations, and insomnia. The estrogenic effects of ginseng may cause breast tenderness and vaginal bleeding. Ginseng may alter bleeding time. It may also alter blood glucose levels, so it should not be used by diabetic patients.

Drug interactions: Ginseng has been said to have interfered in the diuretic action of furosemide. It has been shown to have an additive effect in hormone replacement and corticosteroid therapy. For unknown reasons, Ginseng elevates digoxin levels. Because ginseng appears to have a stimulant effect, it should not be taken concomitantly with other stimulants such as caffeine, ephedra, and sympathomimetics such as epinephrine and amphetamine. Ginseng and phenelzine combinations cause euphoria.


An immune system stimulator, echinacea`s mechanism of action is not completely defined. It is believed to occur from stimulation of phagocytes, inhibition of hyaluronidase, and increased production of fibroblasts, properdin, and interferon.

Echinacea is recommended by herbalists for colds and flu. It should not be taken continuously as a preventative, but only taken at the first sign of a cold or flu and for a period of 14 days. It should not be taken for more than six weeks at a time, since some studies have shown that continuous use actually caused immunosuppression. The recommended dosage is 380 mg to 760 mg three times a day.

Precautions: Echinacea is contraindicated in patients with any type of autoimmune disease, AIDS, tuberculosis, multiple sclerosis, and collagen diseases. It should not be taken continuously by anyone, regardless of the state of health of the individual. Allergies have occurred in very rare incidences.

Drug interactions: Echinacea interferes with the actions of corticosteroids and cyclosporins. Could cause hepatotoxicity and should not be taken with other hepatotoxic drugs such as ketoconazole or methotrexate.

St. John`s Wort

Studies in Germany have shown that St. John`s Wort is as effective as standard antidepressants in the treatment of mild to moderate depression. The mechanism of action of St. John`s Wort is not exactly known, but it is believed to be a combination of low-grade monoamine oxidase inhibition and norepinephrine and serotonin-reuptake blockade. Studies conducted have only been six weeks in length, therefore taking the herb for longer periods is contraindicated until further research assures its safety. The recommended dosage is 300 mg three times a day.

Precautions: The herb has a high safety profile for six-week periods. Adverse effects are usually limited to gastrointestinal symptoms, dizziness, confusion, tiredness, and sedation. Less than 1 percent of patients in the studies had serious photosensitivity reactions. Orthostatic hypotension is a common adverse effect of most antidepressants, and a few incidences of this type of syncope have occurred in patients taking St. John`s Wort.

Drug interactions: St. John`s Wort should not be taken with other antidepressants, tranquilizers, psychoactive, or mood-altering drugs.

Saw Palmetto

In Germany, 90 percent of patients with benign prostatic hyperplasia are taking Saw Palmetto instead of other forms of treatment. Studies have shown that Saw Palmetto is as effective as finasteride, which is a prescribed drug whose mechanism of action is to inhibit 5 alpha-reductase. The enzyme 5 alpha-reductase converts testosterone to dihydroxytestosterone, which causes the enlargement of the prostate gland. Blocking this conversion prevents the enlargement of the prostate gland.

Consequently, herbalists are recommending that men start taking Saw Palmetto when they reach 40 years of age to prevent the condition. Saw Palmetto produces significantly fewer side effects that finasteride. Many patients in the United States are treated with alpha 1 antagonists, since they are more effective than either finasteride or Saw Palmetto. The recommended dosage of Saw Palmetto is 160 mg twice daily of standardized extract containing 85 to 95 percent fatty acids and sterols.

Precautions: Saw Palmetto causes rare side effects that include gastrointestinal disturbance and headaches. Some Saw Palmetto products contain tannic acids, which may inhibit the absorption of iron.

Drug interactions: Saw Palmetto could have a synergistic effect with hormonal therapy used in benign prostatic hyperplasia. Patients should discuss their treatment with their physician and not take any herbs without the physician`s consent.


This herb has been involved in several studies with some conflicting results. Yet research has shown that Feverfew does prevent migraine headaches. It will not relieve the headache if taken after the symptoms present themselves, but many patients reported fewer migraines when Feverfew was taken daily as a preventive measure. Feverfew seems to have an anti-inflammatory effect that inhibits phagocytosis, platelet aggregation, and the secretion of inflammatory mediators. It is comparable to prescription drugs that contain beta-blockers, or valproic acid. The recommended dosage is 125 mg daily of encapsulated leaves standardized to contain 0.2 percent parthenolide.

Precautions: The side effects of Feverfew occur in 5 to 15 percent of users. Dental professionals, in particular, should be aware of them, since the most common is oral aphthous ulcers and swollen tongue. Gastrointestinal irritation is another common adverse effect, and rebound headaches are common to those who suddenly discontinue taking Feverfew. Allergic reaction is a rare adverse effect.

Drug interactions: Other nonsteroidal anti-inflammatory drugs may cancel out the effects of Feverfew. Feverfew may alter bleeding time and should not be used with warfarin.


European clinical trials have shown that Valerian is effective as a mild sedative and/or a sleeping aid. It has a mechanism of action that is similar to the antianxiety agents from the benzodiazepine drug group. The clinical effects are much milder than those produced by benzodiazepines, yet significantly improved sleep quality and decreased sleep latency are produced by Valerian.

Studies have conflicting information with regard to drowsiness and morning sedation. Some claim there is no residual sedation in the morning, while others claim it causes morning drowsiness, fatigue, and ataxia. It does not seem to be habit-forming. It is not synergistic with alcohol, but studies on its interaction with other CNS depressants are inconclusive at this time. The daily recommended dosage is 1 to 3 mg three times a day.

Precautions: There have been a few reports of paradoxical stimulation, restlessness, and heart palpitations (particularly after long-term use). A few cases of liver toxicity have been reported. In vitro testing has shown that some components of Valerian are cytotoxic and mutagenic. However, even in high doses, these effects have not been seen in vivo.

Drug interactions: Valerian should not be taken with barbiturates and other CNS depressants. The combination could cause increased sedative effects.

Listed as questionable

Some common herbs whose efficacy and safety are questionable include the following examples.


This herb has been used separately or in combination with herbal diet remedies. Herbalists claim that Kava has muscle relaxant, hypnotic, analgesic, and weight-reduction properties. There is not enough evidence to support such claims.

Precautions: There have been numerous adverse effects reported with the long-term heavy consumption of Kava (310 to 440 grams per week). They include excessive weight loss, malnutrition, and liver and renal dysfunction. Other adverse effects reported with Kava at various doses include lymphopenia, decreased platelet volume, red blood cell macrocytosis, neurologic effects, and inhibiting of B-vitamins. Anorexia and pulmonary hypertension, the same adverse effects common to fenfluramine, are common to Kava. Hepatotoxic effects have been reported, mostly in combination with alcohol.

Of particular interest to dental professionals are the adverse oral effects of the kava beverage, such as numbing of the mouth and tongue. Other adverse effects associated with 100 to 450mg per day of Kava preparations include extrapyramidal effects, involuntary oral and lingual dyskinesia, torticollis, oculogyric crisis, and exacerbation of Parkinson`s disease.

Drug interactions: Kava caused a coma in an individual who was taking alprazolam. It should not be taken with alcohol, CNS depressants, anticoagulants, aspirin, antipsychotics, and drugs used in the treatment of Parkinson`s disease.


Also known as Ma huang, Ephedra has approximately 40 species that have alkaloids containing ephedrine and pseudoephedrine. Ephedra is used to treat asthma, allergies, colds, and obesity. It may be found in numerous weight-loss remedies. Studies have shown that it is relatively ineffective for the treatment of obesity. Ephedra is considered a circulatory stimulant. The anorexant effects are supposed to come from an increase in metabolism that results from increasing blood pressure and heart rate.

Precautions: Although Ephedra is effective for bronchodilation, it is unsafe for patients with hypertension, diabetes, or thyroid disorders. It can cause insomnia, palpitations, dizziness, headaches, and nervousness. Patients should be told of the adverse effects and risks of taking this herb. Patients with undiagnosed cardiac or endocrine disorders could experience serious adverse reactions.

Drug Interactions: Ephedra should not be taken with other stimulants such as caffeine, epinephrine, amphetamines, etc.

Evening Primrose Oil

There is conflicting research on the efficacy of Evening Primrose Oil. Herbalists claim it is effective in the treatment of Ohot flashesO (vasospasms associated with menopause), PMS, weight loss, skin rashes, depression, and other maladies.

Precautions: There is no data to support its absolute effectiveness or safety over the long term.

Drug Interactions: Evening Primrose Oil interferes with the effectiveness of anticonvulsants by lowering the seizure threshold.

With more research, we will discover all of the benefits and risks associated with herbal medicine. In the interim, extreme caution should be used when taking any herbs, especially in combination with other prescribed or over-the-counter medications. Make patients aware that OnaturalO does not necessarily mean Osafe.O


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Cynthia R. Biron, RDH, is chair of the dental hygiene program at the Tallahassee Community College. She is also a certified emergency medical technician.