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David Baxter PhD

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Dangerous combinations: Pharmaceuticals and herbs
By Hege J. Tunstad
Tue, Nov 13 2007

Medicines and herbal remedies are not always a good combination. Some combinations could be fatal - but which ones?

The health foods industry is large and diverse, and a lot of people take different types of dietary supplements and herbal remedies. Whether they are necessary or have any effect what so ever, is much discussed, but we still take them, just in case. And natural herbal products can't hurt, can they?

In the doctor's office, we find posters urging us to tell our doctor which health food products we eat. And there is a reason for that: Herbal remedies and medication affect one another in your body. It is almost like mixing wine and beer - the effect is unpredictable and not always positive. The result could in the worst case be fatal.

Like if you wish to increase the effect of Viagra by flushing it down with grapefruit juice - tempting, perhaps, but the potential adverse effects include both angina and cardiac infarction. Or if you take some St John's Wort as a tranquilizer - then Viagra might not live up to your expectations.

St John's Wort reduces the effectiveness of many medications. Women need to be aware that birth control pills are not reliable when taken with St John's Wort supplements.

But how are we as consumers supposed to know which combinations produce which effects?

Help is on its way. A group of research scientists at the Norwegian University of Science and Technology (NTNU) Faculty of Medicine are establishing methods that could reveal which combinations of herbs and medication are harmful and which are safe. The project is financed by the Research Council of Norway and the Norwegian Cancer Society.

"We are testing what happens when mixing popular herbs with ordinary medication," says Project Manager, Professor Odd Georg Nilsen.

"We cannot say for sure whether garlic strengthens our immune system. But we will provide an answer to whether garlic and other herbal remedies alter the effect of ordinary medication. Our current information on the combined effects of herbal remedies and medication is highly insufficient. Particularly considering the fact that the Norwegian Medicines Agency has an overview of herbs that classifies several hundred different products as merchandise or medication over the counter or on prescription."

Anything you eat, be it food, drink or medication, goes into your stomach and through the digestive organs. Everything is put into the same soup of gastric acid, and digestive enzymes.

A medication's effectiveness depends upon the dosage being right for you. Often, the dose must be adjusted according to any other medication. Pharmaceutical drugs affect one another, and your doctor will check the Physician's Desk Reference to determine if the medications you are taking will work together. Some drugs intensify each other while others weaken each other.

However, if you take herbal remedies together with your medication, there is very little information in the PDR about whether the combination will affect your medication.

The NTNU researchers aim to produce a systematic overview of the effects different herbal remedies could have in combination with different drugs. The methods they are using will reveal whether the herbal remedies need to queue up with different drugs on their way through our bodies.

It is when the drugs and the herbs are fighting for space in the body's systems that the effect of the drugs is influenced. This competition mainly takes place in the intestines and the liver. The intestines regulate how quickly the drugs are absorbed into the body. The liver produces enzymes that regulate how quickly medication is broken down and eliminated from your body.

"We all know what it is like when there is a queue in front of a door," Nilsen says. "People are piling up, and the strongest or most impertinent ones get in first. It is the same with herbal remedies and medication standing in front of the same gate and wanting to go through."

If the herbal remedy is the strongest, the medication will move more slowly to the place where it is needed. The result is reduced or delayed effect. If elimination is restrained, then the medication may accumulate and produce a stronger effect, perhaps with adverse consequences.

Medical mathematics is not simple. If the researchers extract two substances from a herb and test how these affect the effect of a drug, the effects could be totally different when testing each substance separately compared to testing them both as a mixed product. The active substances in a herbal remedy may affect medications diffeently if they are removed from their natural surroundings.

"We are investigating the effect of extracts from the full preparation as it is sold in health food stores and at the chemist's [pharmacy]. You could say that we are testing directly from the case," says Nilsen.

"It is important to remember that drugs and herbal remedies that are said to have identical effects not necessarily reinforce one another, but could actually have the opposite effect," says Professor Nilsen. "The rule about caution still applies. And remember to tell your doctor about what you eat!"

In general, medication with a narrow therapeutic dose range are poorly suited in combination with herbal remedies. The effect of these drugs depends upon a constant amount of the drug being in the bloodstream at all times. Several drugs taken in connection with organ transplants, HIV, mental illnesses, epilepsy and cancer are of this type.

If we combine such medications with herbal remedies that affect the concentration of the drug, the drug's effectiveness could increase or decrease. An increase could produce undesirable adverse effects while a decrease could result in a loss of therapeutic effect.

"It is not always possible to know what could be dangerous," Nilsen stresses.

Organ rejection is one of the problems that could arise. St John's Wort is an example of a herbal that weaken rejection preventing medications. And it is not enough to avoid taking the herbal remedy the day before the operation. The effect of the herbal supplement may last for weeks.

Examples of adverse affects are numerous. Many patients being hospitalized, particularly in the US, have taken herbal remedies before undergoing planned surgery. That could make the anaesthetist's job difficult, and make the result of the operation unpredictable. The herb Valerian, which many people take to calm their nerves, increases the effect of some anesthetics, while Gingko biloba may weaken them. Ginkgo biloba has also proven to produce increased bleeding tendencies during and after surgery.

Nearly half of all cancer patients in Norway resort to herbal remedies to strengthen their health. As many as 70 percent admit to taking herbal remedies to boost their immune system, and the majority hope for improved quality of life. Nobody has told them that the herbs could weaken the effectiveness of their cancer medication.

NTNU researchers have mapped cancer patients' use of herbal remedies. Most of them place their confidence in garlic and green tea. Noni juice is also popular. Even though none of the patients say that they have noticed any adverse affects of the herbal products, researchers have discovered that green tea could increase the effect of certain cancer medication and thus increase the risk of harmful side effects.

Some cancer patients take a product called Agaricus - a Japanese mushroom extract with a price per liter of about US$1 000.00. At that price it would be nice to know whether the product affects your health.

"In our studies, Agaricus seems to increase the effect of other cancer medication," says Research Fellow Silje Engdal. "It is highly worrying that the patients are ripped off financially at the same time as the risk of adverse affects increases."

"We already know that the St John's Wort could reduce the effect of cancer medication so much that it does not produce the desired effect," Engedal says. "Now we know more about how many cancer patients actually use the herbal remedy, which remedies they choose and whether they tell their doctor about it. This information enables us to find out more systematically which combinations the patients need to avoid."

"At the same time, the doctors could have a list of the herbal remedies they should instruct their patients to avoid. We also have a long-term goal of including a list of herbal remedies in the PDR."

Numerous herbal remedies come from the East. The Chinese have used herbs for medical purposes for thousands of years and have a somewhat different view on the use of herbs in combination with drugs. If a certain herb is known to strengthen the effect of a particular drug, the treatment will be performed using a lower dose of medication in combination with the herb in question. The idea is that you will have less adverse affects from the medication since you take less of it, while obtaining full therapeutic effect.

Nilsen and his research team are currently cooperating with several research institutions in China on combination therapy with herbs and pharmaceutical drugs.

"Chinese and herbal remedies are coming into Western medicine. That makes it important to investigate the effect these might have on Western medication," the Professor concludes.
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