Review of Abnormal Laboratory Test Results and Toxic Effects Due to Use of Herbal Medicines

from American Journal of Clinical Pathology
Posted 07/29/2003

Herbal medicines are used widely in the United States, and according to a recent survey, the majority of people who use herbal medicines do not inform their physicians about their use. Herbal medicines can cause abnormal test results and confusion in proper diagnosis. Herbal medicines can alter test results by direct interference with certain immunoassays. Drug-herb interactions can result in unexpected concentrations of therapeutic drugs. For example, low concentrations of several drugs (eg, cyclosporine, theophylline, digoxin) can be observed in patients who initiated self-medication with St John's wort. Herbal medicines can alter physiology, and these changes can be reflected in abnormal test results. For example, kava-kava can cause drug-induced hepatitis, leading to unexpected high concentrations of liver enzymes. Use of toxic herbal products such as ma huang (an ephedra-containing herbal product), Chan Su, and comfrey may cause death. Other toxic effects of herbal medicines include cardiovascular toxic effects, hematologic toxic effects, neurotoxic effects, nephrotoxic effects, carcinogenic effects, and allergic reactions.

INTRODUCTION

Herbal medicines, including Chinese herbal products, are readily available in the United States from health food stores without prescriptions. Ayurvedic medicines are used widely in India, and some preparations are available in the United States. Ginseng, St John's wort, ma huang, kava, ginkgo biloba, Dan Shen, feverfew, garlic, ginger, saw palmetto, comfrey, pokeweed, hawthorn, dong quai, and cat's claw are used by the general population in the United States. Intended uses of common herbal medicines are given in Table 1.(See below) Gulla et al published a survey of 369 patient-escort pairs and reported that 174 patients (47.2%) used herbs. The most common herbal product used was ginseng (20%) followed by echinacea (19%), ginkgo biloba (15%), and St John's wort (14%).

Several herbal products interfere with immunoassays used for monitoring the concentrations of therapeutic drugs. Herbal medicines also can cause toxic effects, leading to abnormal test results. Therefore, the common belief that anything natural is safe is not correct. This review summarizes abnormal test results associated with the use of herbal medicines, as well as interactions between Western medicines and herbal products. This review also summarizes the toxic effects of commonly used herbal products.

REGULATORY ISSUES AFFECTING HERBAL MEDICINES

The US Food and Drug administration (FDA) mandates that only medicines have to be proven to be safe before being released into the market. Herbal products do not fall under the category of drugs as long as they are not marketed for the prevention of any diseases, and, as such, FDA approval is not needed.

Herbal products are classified as "dietary supplements" and are marketed pursuant to the Dietary Supplement Health and Education act of 1994. However, herbal products are regulated differently in other countries. In the United Kingdom, any product not granted a license as a medical product by the Medicines Control Agency is treated as a food, and no health claim or medical advice can be given on the label.

Similarly, herbal products are sold as dietary supplements in the Netherlands. In Germany, herbal monographs are prepared by an interdisciplinary committee (German Commission E), using historic information; chemical, pharmacologic, clinical, and toxicologic studies; case reports; epidemiologic data; and unpublished manufacturers' data. If an herb has an approved monograph, it can be marketed.

Tables for: Review of Abnormal Laboratory Test Results and Toxic Effects Due to Use of Herbal Medicines