Herbs & Lab Tests
Recent surveys indicate that more than 50% of the population use some form of complementary and alternative medicine. In the United States, the sale of herbal medicines now exceeds $4 billion per year. Marketing campaigns often imply that any natural product is safe. However, herbal medicines are classified as dietary supplements and do not have to be proven safe before being released into the marketplace. Many herbs have been associated with adverse effects due to: Abnormal results may occur by any of the following mechanisms:
- Assay interference
- Herb-therapeutic drug interaction
- Organ toxicity
- The most common abnormalities are summarized below.
Common Name |
Other Names
|
Intended Use
|
Adverse Effects
|
Aristolochic Acid |
Snakeroot, birthroot, snakeweed, sangree root, serpentary, wild ginger |
traditional Chinese herbs |
nephrotoxicity, carcinogenic |
Bitter Orange |
Citrus aurantium, zhi xhi, zhi oiao, zhiqiao, kijitsu, neroli oil, Shangzhou, |
weight loss, stimulant, athletic performance |
tachycardia, vasoconstriction, hypertension, stroke |
Borage oil |
Borago officinalis, bee plant, bee bread, ox’s tongue, starflower oil |
rheumatoid arthritis, hypertension |
hepatotoxicity, lower seizure threshold, increase warfarin effect |
Cat's Claw |
Uncaria tomentosus, Una de gato, hawks claw |
anti-viral, prevent colds & flu, chronic fatigue syndrome |
hypotension, diarrhea, increase warfarin effect, inhibit CYP3A4 |
Chan Su |
Chinese toad auricular glands |
tonsillitis, sore throat, palpitations, heart tonic |
vasoconstriction, hypertension, arrhythmia, digoxin immunoreactivity |
Chaparral |
Larrea tridentata, creosote bush, jarilla, greasewood, hediondilla |
anti-neoplastic, anti-oxidant, arthritis remedy, cleansing tonic |
cholestatic hepatotoxicity, nephrotoxicity, carcinogenic |
Comfrey |
Symphytum officinale, knitbone, nipbone, black root, bruisewort, consolidae radix |
inflamed joints, wounds, gout, fractures, thrombophlebitis |
hepatic veno-occlusive disease |
Dan Shen |
Salvia miltiorrhiza |
angina pectoris, cardiovascular diseases |
digoxin immunoreactivity, increase warfarin effect, platelet inhibition, fibrinolysis |
Dong quai |
Angelica senensis |
menopause & menstruation |
increase warfarin effect |
Echinacea |
Purple cone flower |
colds, flu, URI, UTI, immune stimulant |
allergic reactions, nausea, myalgia, hepatitis |
Ephedra |
Ma huang |
weight loss, stimulant, athletic performance |
arrhythmia, hypertension, stroke |
Evening Primrose |
Oenothera biennis, primrose oil |
breast tenderness, PMS |
lower seizure threshold |
Feverfew |
Tanacetum parthenium, Chrysanthemum |
headaches, migraines, menstrual cramps, arthritis |
increase warfarin effect |
Garlic |
Allium sativum |
lower blood pressure & cholesterol |
increase warfarin effect, platelet inhibition |
Germander |
Teucrium chamaedrys |
weight loss, general tonic |
cholestatic hepatotoxicity |
Ginger |
motion & morning sickness |
increase warfarin effect |
|
Ginkgo biloba |
Maiden hair tree |
forgetfulness, mental focus, tinnitus, claudication |
increase warfarin effect, platelet inhibition, hypertension, seizures |
Ginseng |
Eleutherococcus senticosus (Siberian), Panax ginseng (Asian) |
stress, endurance |
decrease warfarin effect, digoxin immunoreactivity, hypoglycemia, Stevens Johnson, schizophrenia |
Green tea |
Camellia sinensis |
cancer prevention, heart tonic, nausea & vomiting |
decrease warfarin effect |
Kava kava |
Piper methysticum, kawa, ava, awa, gea ,gi, kao, kew, malohu, yagona, sakau |
anxiety, insomnia |
hepatoxicity, parkonsonism, GABA receptor blockade, calcium & sodium channel blockade |
Kelp |
anti-inflammatory, thyroid tonic, metabolic tonic |
hyperthyroidism |
|
Licorice root |
anti-inflammatory, peptic ulcers |
aldosteronism, hypokalemic myopathy, hypertension, increase warfarin effect |
|
Lobelia |
Lobelia inflata, Pokeweed, Indian tobacco, cardinal flower, asthma weed |
anti-viral, anti-neoplastic |
arrhythmia, respiratory failure |
Lu Shen Wan |
heart tonic |
falsely elevated digoxin levels |
|
Mistletoe |
digestive aid, sedative, heart tonic |
hepatotoxicity |
|
Moonflower |
Daturia inoxia |
hallucinogen |
seizures, hallucinations, coma |
Oleandrin |
Nerium oleander, dogbane, Thevetia peruviana, rose laurel |
cancer, HIV, hepatitis, psoriasis, rheumatoid arthritis |
arrhythmia, contact dermatitis, digoxin immunoreactivity, N&V, diarrhea, salivation, altered mentation |
Passion flower |
Passiflora incarnata |
insomnia, anxiety |
arrhythmia, drowsiness |
Pennyroyal |
Mentha puleguim, Hedeoma pulegoides, squawmint, mosquito plant, tickweed |
induce menstruation, abortifacient, gout, fleas |
hepatoxicity, nephrotoxicity, seizures |
Pentagyn |
Gynostemma pentaphyllum, Jiaogulan, miracle grass, Xianxio, Southern Ginseng |
lower BP & cholesterol |
increase warfarin effect, nausea, diarrhea |
St. John's Wort |
Hypericum perforatum, goat weed |
mood disorders, depression |
induces CYP3A4 & P-glycoprotein drug transporter, increased drug clearance, lower therapeutic drug levels |
Saw Palmetto |
Serenoa serrulata, Sabal serrulata, saw tooth palm |
BPH, polycystic ovary syndrome, hirsutism |
5-alpha reductase inhibition, testosterone metabolism inhibition |
Skullcap |
Scutellaria laterifolia, pimpernel, hoodwort, monkey flower, mad-dog weed, quaker bonnet |
insomnia, irritability, nervousness, snakebites, rabies |
hepatotoxic, giddiness, stupor, confusion, seizures |
Valerian root |
Valeriana officinalis, capon's tail |
Insomnia, anxiety |
neurotransmitter inhibition by enhancing GABA, tachycardia, hypotension, headache, delirium |
Yohimbe |
Corynanthe yohimbe, Pausinystalia yohimbine, yohimbehe, johimbe |
aphrodesiac, impotence |
Tachycardia, hypertension, urinary retention |
Some herbs have structural similarity with digoxin and interfere with the digoxin immunoassay. Digoxin levels may be falsely elevated or decreased depending on the type of assay used in the laboratory. The herbal products that most often interfere with digoxin measurements are Chan Su, Dan Shen, Uzara root, Asian Ginseng and Siberian Ginseng. Fortunately, the Bayer Centaur assay used in the Saint Luke’s Health System is not adversely affected by these herbs.
Several herbal medicines lower the seizure threshold maintained by several anticonvulsants including phenobarbital and phenytoin. The most common offenders are Evening Primrose, Borage Oil and Shankhapushpi. Therapeutic drug levels may decrease up to 40% after ingestion of these products.
Many herbal medicines interact with warfarin and potentiate its anticoagulant effect, increasing the risk of bleeding. Some herbs can produce as much as a two-fold rise in INR. Examples include angelica root, arnica flower, ansine, bogbean, borage seed oil, Boldo-genugreek, capsicum, Dan Shen, Dong Quai, feverfew, garlic, ginger, Ginkgo biloba, licorice root and willow bark.
Other herbal medicines interfere with warfarin’s anticoagulant properties, leading to subtherapeutic INR values. In some cases, these herbs have been reported to decrease INR as much as 50%. The main culprits are ginseng, Saint John’s Wort and soy milk.
Some herbs can increase the risk of bleeding by inhibiting platelet aggregation. The best known examples are Dan Shen, garlic and Ginkgo biloba.
Besides interfering with warfarin, Saint John’s Wort has been reported to decrease the therapeutic concentration of several other medications. St. John’s wort induces the CPY3A4 mixed function oxidase, which is responsible for metabolism of 45% of CYP450 mediated drug metabolism. It also induces the P-glycoprotein drug transporter, reducing the efficacy of drugs in which hepatic metabolism is not the major pathway of clearance. Self medication with St. John’s wort can cause treatment failures due to an increase in the clearance of many prescribed medications. Examples include oral contraceptives, immuno-suppressants, HIV protease inhibitors, HIV non-nucleoside reverse transcriptase inhibitors, cardiac drugs and anti-neoplastic drugs such as irinotecan and imatinib mesylate. Specific examples include:
- Lower concentrations in oral contraceptives may cause failed birth control.
- A rapid and significant reduction in cyclosporine and tacrolimus concentrations in transplant patients may cause rejection.
- A reduction in the AUC of indinavir by a mean of 57% and the trough level by 81%. Atazanavir lopinavir and ritonavir are similarly affected.
- A decrease in the therapeutic level of theophylline requiring an increase in dosage from 300 mg bid to 800 mg bid.
- Significantly decreased methadone levels, resulting in reappearance of withdrawal symptoms.
- Significantly reduced levels of simvastatin, resulting in decreased cholesterol lowering effect. However, Pravastatin is not affected.
- Decreased digoxin trough levels by 33% and peak levels by 26%.
- Verapamil clearance is significantly increased.
Different brands of St. John’s wort may vary widely in the magnitude of these effects, because herbal supplements are not subject to rigorous pharmaceutical standards.
Some herbal medicines are hepatotoxic. Kava is the most notorious hepatotoxin and can produce a 70 fold increase in ALT and AST. Mistletoe berries have also been reported to elevate ALT and AST. Chaparral and germander have been associated with cholestatic hepatitis. Comfrey may cause hepatic veno-occlusive disease.
Kelp is promoted as a thyroid tonic and anti-inflammatory medicine. Kelp tablets contain substantial amounts of iodine, which can cause hyperthyroidism. T4 and T3 are increased, while TSH is suppressed.
Some herbal medicines affect glucose levels. Chromium is a trace metal that helps to regulate glucose metabolism. Athletes and bodybuilders take chromium supplements to enhance performance. Large doses can induce hyperglycemia. In contrast, ginseng has been associated with hypoglycemic episodes.
Licorice is used as an anti-inflammatory herb and as a remedy for peptic ulcers. Carbenoxolone, one of the components of licorice, can elevate blood pressure and cause hypokalemia. In extreme cases, licorice ingestion has been associated with hypokalemic myopathy. In these cases the mean plasma potassium level is 1.98 mEq/L and the mean CK level is 5300 IU/L.
Unexpected lead poisoning may occur from the use of herbal medicines contaminated with lead. Some Chinese herbs have been found to have lead content as high as 20,000 ppm. Ingestion of these products can lead to blood lead levels exceeding 100 ug/dL. Some patients may present with intoxication porphyria secondary to lead poisoning.
Because of these complications, the American Society of Anesthesiologists has suggested that in general patients should discontinue their herbal medicines at least 2 weeks before surgery. Other investigators have recommended that those herbal medicines that interfere with platelet function or coagulation should be discontinued at least 7 days prior to surgery.
In summary, herbal medicines should be considered whenever an otherwise healthy individual has an abnormal laboratory result. They should also be considered whenever a patient has an unexpected response to a prescribed medication or presents with unexplained organ toxicity.