St. John's Wort - Drugs & Vitamins - Drug Library

Scientific Name: St. John's Wort
Other Names: Amber Touch-and-Heal, Hardhay, Hypericum, Hypericum perforatum, Klamath Weed, Millepertuis, Rosin Rose, SJW, Tipton Weed

Who is this for?

Uses

Used from time to time since ancient days to treat a number of various conditions, St. John's wort has become popular again as an antidepressant. It contains several chemicals, including hypericin, hyperforin, and pseudohypericin, which are thought to be the major sources of its antidepressant activity. In several studies of laboratory animals and humans, one or more of the chemicals in St. John's wort appeared to delay or decrease re-absorption of the neurotransmitters dopamine, norepinephrine, and serotonin by nerve cells. Neurotransmitters are chemicals that carry messages from nerve cells to other cells. Ordinarily, once the message has been delivered, neurotransmitters are re-absorbed and inactivated by the cells that released them. Chemicals in St. John's wort may keep more of these antidepressant neurotransmitters available for the body to use. Multiple studies have shown that St. John's wort may be effective in relieving mild to moderate depression, although maximum antidepressant effects may take several weeks to develop.

However, other studies have challenged the antidepressant effects of St. John's wort. At least two recent large, well-controlled clinical studies found no difference in relief of major depression among individuals who received St. John's wort and those taking placebo (inactive sugar pills). In one of the studies, a prescription antidepressant medication also showed no significant effect on major depression. Whether the studies lasted long enough and whether the doses of antidepressants and St. John's wort were high enough to produce significant effects may be questionable. In 2003, the U.S. National Institute of Mental Health began a 4-year clinical study to compare the effectiveness of St. Johns wort with both a prescription antidepressant and placebo for treating mild depression. Results of that study have not yet been published

In addition to its potential for depression, St. John's wort has also been studied for the treatment of other emotional disorders such as anxiety, obsessive-compulsive disorder (OCD), menopausal mood swings, and premenstrual syndrome. It is believed that chemicals in St. John's wort may act like other chemicals that are associated with relieving emotional conditions. These effects are poorly understood; however, and results of the studies are mixed, with a few finding possible effectiveness and others finding no difference between placebo and St. John's wort. Currently, studies sponsored by the National Center for Complementary and Alternative Medicine, a part of the U.S. National Institutes of Health, are underway to test the effectiveness of St. John's wort for OCD and social phobia as compared to placebo. More studies are planned for determining the usefulness of St. John's wort in treating these mental conditions.

In laboratory studies, St. John's wort has shown some effectiveness for lessening the symptoms of nicotine or alcohol withdrawal and for reducing the craving for alcohol in addicted animals. In one small human study, about 35% of smokers who took St. John's wort while they were trying to quit maintained smoking cessation for at least 12 weeks.

Possible antiviral effects of St. John's wort are being investigated for the treatment of HIV/AIDS, hepatitis C, and other viral illnesses. Hypericin, pseudohypericin, and other chemicals in St. John's wort are thought to stick to the surfaces of viruses and keep them from binding to host cells. Another theory is that St. John's wort may contain chemicals that interfere with the production or release of viral particles. This antiviral activity is enhanced greatly by exposure to light. However, the doses needed for active antiviral effect from St. John's wort may be so high that unbearable side effects may limit its usefulness as an oral antiviral. More research is needed to prove or disprove the effectiveness and to determine effective dose levels of St. John's wort for viral illnesses.

Although taking it orally is more common, St. John's wort may also be applied to the skin. In some parts of Europe, it is used widely as a treatment for topical infections. It has mild antibiotic effects, which are thought to be attributed mainly to its hypericin content, although a cream containing 1.5% hyperforin has also been found useful in studies for treating dermatitis. Hypericin also seems to have an additional anti-inflammatory effect caused by interrupting the body's production of natural chemicals that promote inflammation. Additionally, St. John's wort contains between 3% and 15% of a chemical group known as tannins, which act as astringents. An astringent shrinks and tightens the top layers of skin or mucous membranes, thereby reducing secretions, relieving irritation, and improving tissue firmness. St. John's wort may also promote the healing of broken skin by speeding up the skin's production of protein fibers. All these properties may make topical St. John's wort moderately useful for minor skin irritations such as cuts, razor burn, and scrapes. Studies comparing long-term use of topical St. John's wort against prescription treatments that are applied for skin conditions are needed to determine its true effectivenes, however.

In very early studies, the ability of St. John's wort to sensitize the skin to ultraviolet (UV) light has been tested as a treatment for skin cancers and other skin conditions. In small studies of humans, individuals took St. John's wort orally and thenthe affected areas of skin were exposed to UV light two hours later. In general, the results have been mixed with some individuals experiencing complete elimination of the conditions, but most achieving only partial response or no improvement. All study participants found the treatment painful, however, and much more study is needed to prove or disprove its effectiveness.

When should I be careful taking it?

In animal studies, oral doses of St. John's wort have caused the muscles of the uterus to tighten, possibly causing a miscarriage. Whether enough of topically applied products are absorbed to cause a similar effect is not known. Although no human miscarriages have been attributed to taking or using St. John's wort, pregnant women should avoid it.

Individuals who have received a transplanted heart, kidney, liver, lungs or other organ should not take or use St. John's wort because it has been shown to interfere with the medications needed by transplant recipients.

St. John's wort may cause or worsen mental conditions for individuals with Alzheimer's disease, bipolar disorder, or schizophrenia. Cases of psychosis (not being able to tell what is real from what is imagined) or mania (excessive happiness) have been reported after patients with a previously diagnosed mental illness took St. John's wort.

Precautions

Even though small amounts of St. John's wort have been found in the breast milk of new mothers who take it, very little of the active ingredients were detected in the blood of their infants. Those babies may have a slightly higher risk of fatigue or colic, however.

High doses of oral St. John's wort appeared to impair fertility among female study animals and affect sperm activity among males. No similar results have been reported from humans who take St. John's wort, but one case has been documented of sexual malfunction in a man who took St. John's wort for 9 months. Couples who are trying to conceive a child are advised to avoid taking St. John's wort.

In study animals, St. John's wort has extended the time that food and other substances stay in the stomach. While not usually serious, delayed stomach emptying may interfere with treatment for diabetes and it may result in bloating, heartburn, nausea, or weight loss.

What side effects should I watch for?

Major Side Effects

Rare cases of serotonin syndrome, a potentially dangerous oversupply of the neurotransmitter serotonin in the body, have been attributed to taking St. John's wort. Neurotransmitters are natural body chemicals that carry messages from nerve cells to other cells. Uncontrolled serotonin syndrome may result in coma, seizures, and death. Symptoms of serotonin syndrome include:

Confusion
Euphoria
Fever
Hallucinations
Inability to coordinate muscles
Nausea
Restlessness
Shakiness
Sweating
Vomiting

One case has been documented of intense nose bleeds in an individual who had inserted St. John's wort into the nose. Surgery was needed to stop the bleeding. How often the individual used St. John's wort nasally and how long it was left in the nose are unclear.

Less Severe Side Effects

Both oral and topical forms of St. John's wort may make unprotected skin more sensitive to sunlight or artificial light in sun tanning parlors. Some evidence from case reports also seems to associate a higher risk of cataracts with possible eye sensitization to light when St. John's wort is taken. Laboratory studies have shown that St. John's wort may also contribute to retinal damage caused by light. Individuals who use St. John's wort should be sure to use sunscreen and eye protection when exposed to sunlight or artificial light used for sun tanning.

Other side effects reported from taking St. John's wort by mouth include:

Dizziness
Drowsiness
Dry mouth
Headache
Irritability
Upset stomach

Topically, St. John's wort may cause a rash.

What interactions should I watch for?

Prescription Drugs

In studies, St. John's wort has been shown to increase elimination of the anticoagulant drug, warfarin, from the body. As a result, less warfarin may be available, blood clotting may not be controlled adequately, and blood clots may form. Whether St. Johns wort interferes with the effects of other anticoagulants or similar drugs known as antiplatelets is not yet known. Individuals who take an anticoagulant or an antiplatelet drug should check with a doctor or pharmacist before beginning to take St. John's wort, too.

Antiplatelets include clopidogrel and Ticlid
Anticoagulants include heparin and warfarin

In some cases, when St. John's wort was taken at the same time as certain prescription antidepressants, more side effects were experienced. These side effects included fatigue, nausea, restlessness, sweating, and vomiting. Among the drugs involved were:

Monoamine oxidase inhibitors such as Marplan, Nardil, and tranylcypromine (Parnate)
nefazodone
Selective serotonin reuptake inhibitors (SSRIs) such as fluoxetine, paroxetine, and sertraline
Tricyclic antidepressants such as amitriptyline and nortriptyline

Because it is broken down by certain enzymes in the liver, St. John's wort may possibly interfere with the use of prescription drugs that are processed by the same enzymes. Some of these drugs are:

Allergy drugs such as fexofenadine
Antifungal drugs such as itraconazole and ketoconazole
Cancer drugs such as Camptosar, etoposide, Gleevec, paclitaxel (Taxol), vinblastine, or vincristine
Certain calcium channel blockers such as diltiazem and nifedipine

St. John's wort is believed to affect the amounts of a body chemical known as P-glycoprotein, which serves as a carrier for many types of drugs, including digoxin. When St. John's wort and digoxin are taken together, the blood levels of digoxin may decrease significantly and the control of heart conditions treated by digoxin may not be maintained. St. John's wort should not be taken with digoxin.

By altering enzyme activity, St. John's wort appears to lower blood levels of at least two classes of drugs that are used to treat HIV and AIDS. St. John's wort should be avoided by individuals who take non-nucleoside reverse transcriptase inhibitors such as delavirdine (Rescriptor) and nevirapine (Viramune) and protease inhibitors such as indinavir (Crixivan), ritonavir (Norvir), and nelfinavir (Viracept). The effects of St. John's wort on other classes of drugs used to treat HIV-related conditions is not known, but individuals who are taking any anti-HIV drugs may want to avoid taking St. John's wort.

St. John's wort may activate enzymes that break down certain drugs; therefore, it may interfere with the effects of drugs used to suppress the immune system after organ transplants or in other conditions. Taking St. John's wort is not recommended for patients who take drugs such as:

azathioprine (Imuran)
CellCept
cyclosporine (Neoral, Sandimmune)
Prograf
Rapamune
Zenapax

St. John's wort may interfere with the body's use of oral contraceptives. Irregular vaginal bleeding may result and contraceptives may not be as effective. To prevent unplanned pregnancy, women who take St. John's wort should use an additional form of birth control different from oral contraceptives.

In small studies of healthy individuals, St. John's wort reduced the the effectiveness of the anti-cholesterol drugs, atorvastatin (Lipitor) and simvastatin (Zocor). Levels of a similar drug, pravastatin (Pravachol), were not changed. Other drugs in the class known as statins (Crestor, Lescol, and lovastatin) may be affected by St. John's wort. Therefore, individuals using one of the statin drugs to reduce cholesterol should not start taking St. John's wort until a doctor or pharmacist determines the potential for an interaction.

In a recent study, taking St. John's wort reduced the amounts of omeprazole (Prilosec) in the blood. As a result, the effects of omeprazole were much less than expected. Omeprazole belongs to a class of drugs known as proton pump inhibitors, which is used to treat ulcers and other gastrointestinal (GI) conditions.

Drugs known as psoralens cause the skin to be excessively sensitive to sunlight. Psoralens include Oxsoralen (methoxsalen or 8-MOP). In addition, some antibiotics such as ciprofloxacin and tetracycline may make the skin more likely to sunburn. If St. John's wort, which also sensitizes the skin to light, is taken at the same time as another of these sun-sensitizing drugs, the chance of sunburn increases.

For unknown reasons, St. John's wort blocks the effects of a heart drug known as reserpine. The two products should not be taken together.

When St. John's wort is used with prescription drugs that promote sleepiness, the effects of the drug may be exaggerated, resulting in sedation or mental impairment. Prescription drugs that can cause sleepiness include:

Anticonvulsants such as carbamazepine, divalproex sodium, phenytoin, and valproic acid
Barbiturates such as phenobarbital
Benzodiazepines such as alprazolam and diazepam
Drugs for insomnia such as Lunesta, Rozerem, zaleplon, and zolpidem
Tricyclic antidepressants such as amitriptyline, amoxapine, doxepin, and nortriptyline

Through a process that is not understood completely, St. John's wort may decrease both the blood levels and the effectiveness of theophylline, a drug used to treat asthma and other breathing conditions. If the two are taken together, breathing may not be controlled adequately and asthma attacks may be more likely to occur. Theophylline has numerous brand names such as Aerolate, T-Phyl, and Uniphyl. Individuals who take an oral medication for asthma should check with a doctor or pharmacist before beginning to take St. John's wort.

If St. John's wort is taken at the same time as one of the drugs that belongs to a class known as triptans, the risk of side effects--including serotonin syndrome--may go up. Triptans are usually taken to relieve the pain of migraine headaches. They include:

Amerge
Axert
Frova
Imitrex
Zomig

Non-prescription Drugs

Dextromethorphan (DM) is an anti-coughing ingredient in many non-prescription cough and cold products such as Nyquil and Robitussin DM. Because it may have an increasing effect on serotonin levels, taking DM with St. John's wort may result in a higher risk of side effects.

Because the tannins in St. John's wort may block the absorption of iron by the body, iron-deficiency anemia is possible. Symptoms of iron-deficiency anemia may include dizziness, fatigue, low blood pressure, and cold, pale skin.

The sleep-producing effects of over-the-counter products containing diphenhydramine or doxylamine can be enhanced by taking St. John's wort at the same time. Diphenhydramine and doxylamine are contained in many non-prescription sleeping pills as well as in some cough and cold products, therefore caution should be used when taking these medications with St. John's wort because excessive drowsiness may result.

Herbal Products

St. John's wort may cause excessive sedation if it is taken with other potentially sedating herbs such as:

Catnip
Hops
Kava
Valerian

Foods

No interactions between St. John's wort and foods have been reported, but drinking alcohol at the same time as using St. John's wort by mouth may result in increased drowsiness.

Some interactions between herbal products and medications can be more severe than others. The best way for you to avoid harmful interactions is to tell your doctor and/or pharmacist what medications you are currently taking, including any over-the-counter products, vitamins, and herbals. For specific information on how St, John's wort interacts with drugs, other herbals, and foods and the severity of those interactions, please use our Drug Interactions Checker to check for possible interactions.

Should I take it?

St. John's wort belongs to a large family of shrub-like weeds that spread rapidly and invade cultivated land unless they are controlled. Believed to be native to Europe, St. John's wort is now found in most temperate climates--especially in dry areas such as the edges of fields and along roadsides. Its name comes from a supposed association with the plant's first blooming and the saint day of St. John the Baptist, which is June 24. In reality, St. John's wort blooms from late May through September depending on the climate. Various parts of the plants produce dyes--ranging from bright yellow through reds to brown and purple. For use in medicine, the yellow flowers are collected in late summer along with the buds, stem tops, and young leaves around them. These so-called flowering tops should be dried quickly to avoid the loss of active chemicals.

St. John's wort has been used on-and-off for centuries to treat many different conditions. As early as the first century, records show that the flowers of St. John's wort were soaked in olive oil, which gradually turned to a reddish color and which was applied to burns, hemorrhoids, and skin injuries. Oil treated with St. John's wort was also taken by mouth for relief of "demonic possession"--possibly due to mood disorders including anxiety and depression. Dried St. John's wort may have mild diuretic (urine increasing) properties, so it has been used as a tea to relieve swelling. More recently, potential antidepressant effects have brought St. John's wort back into popularity. It is currently the most prescribed antidepressant medication in Germany, where it is approved by the German commission E, the German governmental agency that evaluates the safety and effectiveness of herbal products. The United States does not have a comparable agency to evaluate herbal products.

Dosage and Administration

Orally, St. John's wort is available in a number of commercial dosage forms such as capsules, liquid extracts, and tablets. Extracts are concentrated liquid preparations usually made by soaking chopped or mashed plant parts in a liquid such as alcohol, and then straining out the solid parts. A tea may be brewed by soaking 2,000 mg to 4,000 mg (2 grams to 4 grams or about 2 teaspoons to 4 teaspoons) of dried St. John's wort in about 5 ounces of boiling water for 10 minutes to 15 minutes. After the solid particles are strained out, the resulting tea may be taken up to three times a day. Oral St. John's wort may not exert its maximum effects until it has been taken regularly for 4 weeks or longer.

Commercial oral preparations of St. John's wort may be standardized to a hypericin content between 0.2% and 0.3% or to a hyperforin content of 5%. Standardization by the manufacturer should assure the same amount of active ingredient in every batch of the commercial preparation. Standardization of herbal products is not required by the U.S. Food and Drug Administration (FDA), so not every St. John's wort product sold in this country will contain the same amounts of active ingredients. In addition, the amounts and proportions of active chemicals in St. John's wort plants will differ depending on which species was used, on where it was grown, and on how the plants were harvested, processed, and stored.

Recommended oral dosing varies with up to 1,800 mg (1.8 grams) of St. John's wort used in some studies. Some common oral doses used in clinical studies of St. John's wort are:
Condition Standard Dose Frequency Length

Initial Treatment of Mild or Moderate Depression 0.3% hypericin 300 mg Three times a day 8 weeks

0.2% hypericin 250 mg Twice a day 6 weeks

5% hyperforin 300 mg Three times a day 6 weeks

Obsessive-Compulsive Disorder (OCD) 0.3% hypericin 450 mg Twice a day 12 weeks

Premenstrual Syndrome 0.3% hypericin 300 mg Once a day 8 weeks

For topical use, creams that usually contain 1.5% hyperforin and transdermal patches containing 0.3% hypericin are marketed. The cooled tea may also be used as a skin wash or as a poultice, which is a soft cloth that has been soaked in a medication, possibly heated, and applied to an aching or injured area of skin surface. Transdermal patches are applied once a day. Generally, other topical St. John's wort preparations may be applied as often as needed. Individuals who decide to use one of them should follow the directions on the package that is purchased.

Summary

Currently, St. John's wort is best known for possible mildly antidepressant effects, but it is also being studied to treat other mood disorders such as anxiety and obsessive-compulsive disorder. It may have antiviral and antibacterial effects and it has been used topically for skin injuries.

Risks

St. John's wort may cause the rejection of transplanted organs, therefore transplant recipients should not take it. Alzheimer's patients, individuals with mental illnesses, couples trying to conceive a child, and pregnant or breast-feeding women should also avoid it.

Side Effects

Rarely, taking St. John's wort may be associated with "serotonin syndrome"--an excess of the neurotransmitter serotonin that may cause confusion, hallucinations, and seizures. Both oral and topical forms of St. John's wort may make the skin more likely to sunburn. Other possible side effects are generally mild. They may include drowsiness, headache, rash, and upset stomach.

Interactions

If St. John's wort is taken with psoralens or certain antibiotics, the chance of sunburn may increase. St. John's wort may also interfere with the effectiveness of a large number of drugs and herbal products including:

Alcohol
Allergy drugs such as fexofenadine
Antidepressants
Antifungal drugs such as itraconazole and ketoconazole
Cancer drugs such as as Camptosar, Gleevec, paclitaxel, vinblastine, or vincristine
The cholesterol-lowering drugs lovastatin and simvastatin
dextromethorphan (DM)
digoxin
Immunosuppressants such as cyclosporine and Prograf
Iron
Non-nucleoside reverse transcriptase inhibitors such as Rescriptor and Viramune
omeprazole
Oral contraceptives
Protease inhibitors such as Crixivan and Viracept
Reserpine
Sedating drugs and herbals
theophylline
Triptans such as Imitrex

Last Revised April 18, 2008

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Last Revised April 18, 2008

Note: The above information is not intended to replace the advice of your physician, pharmacist, or other healthcare professional. It is not meant to indicate that the use of the product is safe, appropriate, or effective for you.

In general, herbal products are not subject to review or approval by the U.S. Food and Drug Administration (FDA). They are not required to be standardized, meaning that the amounts of active ingredients or contaminants they contain may vary between brands or between different batches of the same brand. Not all of the risks, side effects, or interactions associated with the use of herbal products are known because few reliable studies of their use in humans have been done.

This information is provided for your education only. Please share this information with your healthcare provider and be sure that you talk to your doctor and pharmacist about all the prescription and non-prescription medicines you take before you begin to use any herbal product.

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