Excerpt from

The Essential
Herb-Drug-Vitamin Interaction Guide

by George Grossberg, M.D., and Barry Fox, Ph.D.

Chapter One:

The Warning You Haven’t Heard

Herbs have been used since ancient times to relieve numerous ailments. In the past, people didn’t understand how herbs worked; they only knew that they did. Today we know a lot more about herbs, their contents and chemistry, their mechanisms and uses. We know that when used properly, numerous herbs can be useful health aids. We also know that they cannot be indiscriminately mixed with medications, for herbs and drugs do interact, and the interactions can be harmful.

For example, let’s say that, like many other people, you take St. John’s wort to relieve depression. Then you go to your doctor, who prescribes a medication to deal with a different health issue. No problem, right?

Not if a birth control pill has been prescribed. Taking birth control pills when you’re already taking St. John’s wort can cause breakthrough bleeding and unplanned pregnancy.
Not if an antidepressant, such as Zoloft, has been prescribed. St. John’s wort plus Zoloft can trigger serotonin syndrome, which can cause confusion, fever, hallucinations, nausea, shaking, sweating, vomiting—possibly even coma.
Not if Lanoxin, a medication used to treat heart failure, has been prescribed. St. John’s wort can weaken the drug’s effectiveness and allow your heart to "fade away."

Suppose you’re one of the many people who take echinacea on a regular basis to prevent colds and other upper respiratory tract infections. It’s a safe and natural way to ward off a stuffy nose, scratchy throat, and endless bouts of coughing, right?

Not if you’re taking Tylenol for pain, or statin drugs, such as Zocor and Lipitor, for elevated cholesterol. Combining any of these medicines with echinacea can severely damage your liver.
Not if you ever want to use aspirin, ibuprofen, Celebrex, or other widely used painkillers. Mixing echinacea with these popular pills can increase the likelihood of dangerous uncontrolled bleeding.
Not if your doctor prescribes Lodine for your arthritis. Lodine plus echinacea can lead to severe gastrointestinal problems, including nausea, vomiting, and gastritis.
Eager to keep your mind sharp and ward off Alzheimer’s disease, you diligently take ginkgo biloba every day. A wise precaution, right?
Not if you ever need to use Glucotrol, DiaBeta, or certain other drugs to treat diabetes. Ginkgo biloba can interfere with the action of these medicines and send your blood sugar out of control.
Not if you ever need to take antidepressants like Elavil or Norpramin, or antibiotics such as Cipro. Mixing any of these drugs with ginkgo biloba makes you more likely to have a seizure.

Herbs can be wonderful health aids. But dire results may ensue when certain herbs and standard medications are mixed. Odds are you’re not aware of the thousands of herb–drug combinations that can be harmful. And, unfortunately, your doctor may not be aware of the risks either.

It's Not a Trivial Problem

It’s estimated that 60 million Americans are taking herbs for their headaches, back pain, arthritis, menstrual difficulties, insomnia, depression, anxiety, menopausal symptoms, sexual difficulties, and numerous other problems. Millions of these people are also taking medications with their herbs.

The frightening truth is that an estimated 15 million Americans are at risk of dangerous herb–drug interactions. But who’s informing them of the potential dangers? Typically, no one. An article appearing in the Journal of the American College of Cardiology in 2002 noted that one–third of patients use herbs, "yet most practicing physicians have little knowledge of herbal remedies or their effects."

The Vital Information Few Health Professionals Know

An alarm has been quietly ringing for years. Articles warning of potentially dangerous interactions between common herbs and standard drugs—both prescription and over–the–counter—periodically appear in cardiology journals, cancer journals, family practice journals, anesthesia journals, nursing journals, emergency medicine journals, pharmacology journals, even dental journals. Over and over again, the authors of these articles emphasize the problems that can arise when drugs are prescribed for people who take herbs, then lament the fact that most doctors know so little about herbs and what happens when they are mixed with medicines. But few seem to be listening.

What exactly can go wrong? Herbs can "harm" drugs by interfering with their absorption, reducing their effectiveness inside the body, increasing their effectiveness (which is like taking a drug overdose), and/or boosting their harmful side effects. They can also:

combine with drugs (or other herbs) to create new side effects
alter the results of many laboratory tests
worsen existing diseasestrigger potentially dangerous interactions with foods and other supplements

Yet most people are completely unaware of this.

If You’re Taking an Herb, Beware the Medicine

If you’re taking chaparral, comfrey, echinacea, kava kava, or scullcap, an alarm bell should ring if your doctor prescribes a statin drug for your elevated cholesterol. Mixing Lipitor with any of these herbs can trigger potentially fatal liver damage.

If you’re taking chamomile, feverfew, garlic, ginger, or passion flower, beware of using NSAIDs for your arthritis pain. Combining NSAIDs with any of these herbs can cause intestinal bleeding.

If you’re taking borage seed oil, fennel oil, ginkgo biloba, St. John’s wort, or wormwood, think twice before taking antidepressants. When antidepressants are mixed with any of these herbs, your risk of seizures can increase markedly.

If you’re taking aloe, buckthorn, cascara, Chinese rhubarb, licorice, or senna, beware if your doctor prescribes Vascor for your angina. Adding Vascor to any of these herbs can trigger an irregular heartbeat, which is a potentially fatal condition.

And There’s More You Need to Know

Herb–drug interactions are only the beginning of what you need to know to use herbs safely. Many herbs can also alter the outcome of lab tests and interact in harmful ways with existing diseases, foods, and other supplements.

Herbs and Lab Tests

Taking certain herbs can cause various lab values to rise or fall—and even if it’s only a minor, temporary change, it can distort a doctor’s diagnosis or treatment plan. Here are just a few of the herbs that can alter the results of lab tests:

Black psyllium, used for constipation, can lower the results of tests of blood sugar levels.
Bladderwrack, used for arthritis and thyroid disorders, can increase the results of tests of thyroid-stimulating hormone levels.
Cascara, used as a laxative, can discolor urine, interfering with tests dependent on the color of urine when it's exposed to various substances.
Green tea, used for stomach upset, diarrhea, and headaches, can increase bleeding time and prompt false–positive results on tests for serum urate and certain cancers.
Juniper, used for stomach upset, heartburn, and urinary tract infections, can interfere with urine tests by discoloring the urine.
Lavender, used for insomnia and loss of appetite, can depress the results of cholesterol tests.
Mate, used for depression, ulcers, and inflammation, causes false readings in laboratory tests of uric acid and creatinine in the blood, and tests for the tumors known as neuroblastoma and pheochromocytoma.
Motherwort, used for heart problems, can lower the results of thyroid tests.

Herbs and Diseases

And what if you’re already sick? Did you know that taking herbs might make your condition worse? For example:

Capsicum (cayenne), which is often used to improve digestion, can irritate the gastrointestinal tract. This makes the herb potentially dangerous for those with infectious or inflammatory gastrointestinal problems, such as irritable bowel syndrome.
Echinacea, used for colds, viruses, and other problems, can pump up the autoimmune process. This makes the herb potentially harmful for those suffering from multiple sclerosis and other diseases involving immune system reactions and inflammation. Echinacea can also be detrimental to those with diabetes, HIV infections, or allergies.
Guarana, used for weight loss and fatigue, may aggravate gastric and duodenal ulcers.
Licorice root, used for ulcers, bronchitis, colic, and numerous other ailments, can make it harder for diabetics to keep their blood sugar under control, rob potassium stores, and worsen both hypertension and erectile dysfunction.
Panax ginseng, used for anxiety, nerve pain, and insomnia, can lower blood sugar, which may be dangerous for diabetics. The herb can also interfere with blood coagulation, which can be detrimental to those with bleeding conditions, such as hemophilia. Siberian ginseng can increase blood pressure, which is harmful to those who already have hypertension, and it can increase the severity of both mania and schizophrenia.

Herbs and Foods

Then there are herb–food interactions that can harm you in subtle ways. For example:

Blond psyllium, used for constipation, can decrease the absorption of nutrients from the foods you eat by speeding food through the digestive tract and cutting back on the time available for nutrient absorption.
Guar gum, used as a laxative and a cholesterol–reducing agent, can also interfere with the absorption of nutrients.
Kava kava, used to relieve anxiety and insomnia, can become toxic when mixed with alcohol. Symptoms of kava kava toxicity include headache, dizziness, and stomach upset.

Herbs and Other Supplements

Finally, there are potential problems when herbs are mixed with other supplements. For example:

Angelica root, used as a diuretic, can cause increased bleeding when taken with bogbean, capsicum, chamomile, clove, feverfew, garlic, ginger, ginkgo, licorice, passion flower, or red clover.
Butternut, used for hemorrhoids and gallbladder diseases, can deplete potassium stores when taken with black root, cascara, jalap root, senna leaves, or wild cucumber.
Mixing catnip, which is used for migraines, insomnia, colds, and flu, with capsicum, sassafras, Siberian ginseng, St. John’s wort, stinging nettle, or valerian can increase the odds of suffering from the typical side effects seen with any of these herbs.
Eucalyptus oil, used for cough and inflammation of the respiratory tract, can increase the toxicity of borage, coltsfoot, comfrey, and hound’s tooth.

It’s a rare physician who truly understands the dangers that can arise when herbs are combined with medicines, diseases, foods, and other supplements. Most likely, you’re on your own.

Which Herbs, Which Medicines?

Hundreds of herbs interact with hundreds of medicines. And even popular and seemingly safe herbs such as St. John’s wort, kava kava, valerian, ginkgo biloba, echinacea, ginseng, garlic, aloe, and green tea can become dangerous when combined with certain common drugs.

A host of lesser–known but widely used herbs can also cause dangerous herb–drug interactions, including apple cider vinegar, basil, black cohosh, borage seed oil, cayenne, chamomile, clove, dandelion, feverfew, gotu kola, hawthorn, kombucha tea, lavender, lemon balm, licorice, mistletoe, onion, oregano, passion flower, red clover, red yeast rice, rose hip, saw palmetto, and wheatgrass.

Which drugs do they interact with? So far, studies have shown that over three hundred prescription and nonprescription medicines may interact with herbs, including:

Advil, Motrin, and aspirin, taken for pain, inflammation, and fever
Aleve, taken for arthritis and menstrual difficulties
Allegra, taken for allergies
Ambien, Halcion, and Restoril, taken for insomnia
Benadryl, Sominex, and Sudafed, taken for allergies and to promote sleep
Celebrex, taken for arthritis
Celexa, taken for depression
Cipro, taken for anthrax and various infections
Claritin, taken for seasonal allergies
Colchicine, taken for gout
Concerta and Ritalin, taken for attention deficit hyperactivity disorder
Coumadin, taken to prevent blood clots
Demerol, taken for pain
Dilantin and Thorazine, taken for schizophrenia and seizures
Estrogen, used in birth control pills
Flagyl, used for protozoal and bacterial infections
Lescol, used to lower cholesterol
Lithium, taken for bipolar disorder
Orudis, used for painful menstruation and arthritis
Pepcid and Mylanta, taken for stomach upset and ulcers
Pepto-Bismol, taken for nausea and diarrhea
Plavix, taken as a blood thinner/to prevent blood clots
Prevacid, taken for stomach acid
Prilosec, taken for gastroesophageal reflux disease
Propecia, taken for male pattern baldness
Proscar, taken for prostate enlargement
Prozac, taken for depression and bulimia nervosa
Rheumatrex, taken for arthritis, psoriasis, and cancer
Tegretol, taken for seizures
Valium, taken for anxiety
Xanax, taken for anxiety and panic disorder
Zocor, taken for elevated cholesterol
Zoloft, taken for depression

And many, many more.

Close-up on St. John’s Wort

We know more about the way medicines interact with St. John’s wort than with any other herb. St. John’s wort is one of the best–selling herbs in the United States, used to treat depression, anxiety, fatigue, insomnia, mood disturbances linked to menopause, migraines, and numerous other ailments. It‘s apparently safe when used properly and by itself, but adding medicines to the mix can create potentially serious problems.

St. John's Wort in the Medical Literature

Here’s a sample of the warnings that have appeared in medical journals:

Data from human studies and case reports indicate that St. John’s wort decreased blood concentrations of amitriptyline, cyclosporine, digoxin, fexofenadine, indinavir, methadone, midazolam, nevirapine, phenprocoumon, simvastatin, tacrolimus, theophylline and warfarin…St. John’s wort caused breakthrough bleeding and unplanned pregnancies when used concomitantly with oral contraceptives. It also caused serotonin syndrome when co-administered with selective serotonin–reuptake inhibitors (e.g., sertraline and paroxetine)—Journal of Psychopharmacology, 2004
St. John’s wort significantly induced apparent clearance of both S–warfarin and R–warfarin, which in turn resulted in a significant reduction in pharmacological effect of rac–warfarin.—British Journal of Pharmacology, 2004
When combined with serotonin reuptake inhibitor antidepressants (e.g., sertraline, paroxetine, nefazodone) or buspirone, St. John’s wort can cause serotonergic syndrome.—International Journal of Clinical Pharmacological Therapy, 2004
St. John’s wort can participate in potential pharmacokinetic interactions with anticancer drugs.—Journal of Clinical Oncology, 2004

St. John’s wort can also reduce the blood concentrations (and thus, potentially, the effectiveness) of numerous medicines, including:

Allegra (for allergies)
Coumadin (to thin the blood)
Crixivan (for HIV)
Elavil (for depression)
Lanoxin (to prevent heart failure)
Methadone (for pain and detoxification)
Neoral (to prevent organ rejection)
Pamelor (for depression)
Prograf (to prevent organ rejection)
Theo-lair (for asthma, bronchitis, and emphysema)
Versed (for sedation)
Viramune (for HIV)
Zocor (for elevated cholesterol)

If the standard amount of one of these medicines doesn’t seem to be effective, your doctor may increase the dosage. Then not only will your risk of side effects increase, but if you stop taking your St. John’s wort (or even cut back on it), the blood levels of this medicine will shoot up. Suddenly you can be at risk of a drug overdose!

A second problem with mixing medicines and St. John’s wort is serotonin syndrome. This is a potentially serious problem characterized by confusion, agitation, mania, anxiety, muscle rigidity, tremor, restlessness, shivering, changes in blood pressure, seizures, and even coma. These drugs can trigger serotonin syndrome in people taking St. John’s wort:

Amerge (for migraines)
Celexa (for depression)
Cymbalta (for depression and diabetic neuropathy pain)
Effexor (for depression and anxiety)
Frova (for migraines)
Imitrex (for cluster headaches and migraines)
Lexapro (for depression)
Maxalt (for migraines)
Paxil (for depression and obsessive-compulsive disorder)
Prozac (for depression)
Remeron (for depression)
Zoloft (for depression, post-traumatic stress disorder, and panic disorder)
Zomig (for migraines)

Excerpted from The Essential Herb-Drug-Vitamin Interaction Guide by George T. Grossberg, M.D. and Barry Fox Copyright © 2007 by Barry Fox. Excerpted by permission of Broadway, a division of Random House, Inc. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.