Herbal Medications and Nutritional Supplements

65. Botanicals (Herbal Medications) & Nutritional Supplements

Cathi E. Dennehy, PharmD, & Candy Tsourounis, PharmD. Basic & Clinical Pharmacology – 10th Ed. (2007)


The medical use of botanicals in their natural and unprocessed form undoubtedly began when the first intelligent animals noticed that certain food plants altered particular body functions. Much information exists about the historical use and effectiveness of botanical products. Unfortunately, the quality of this information is extremely variable and much is useless or false. An unbiased and regularly updated compendium of basic and clinical reports regarding botanicals is Pharmacists Letter/Prescribers Letter Natural Medicines Comprehensive Database (see references). A useful evidence-based website, www.naturalstandard.com, is available to institutions. Another compendium is the Report of the German Commission E (a committee that sets standards for herbal medications in that country). Interest in the endocrine effects and possible nutritional benefits of certain purified chemicals such as glucosamine, melatonin, high-dose vitamins, and minerals has led to a parallel development of consumer demand for such substances.

The alternative medicinal substances are distinguished from similar botanical substances used in traditional medicine (morphine, digitalis, atropine, etc) by virtue of being available without a prescription and, unlike over-the-counter medications, being legally considered dietary supplements rather than drugs (thus avoiding conventional Food and Drug Administration oversight). Among the purified chemicals, glucosamine and melatonin are of significant pharmacologic interest.

This chapter provides an evidence-based approach to the pharmacology and clinical efficacy of several of the commonly used and commercially available botanicals and dietary supplements. Ephedrine, the active principle in Ma-huang, is discussed in Chapter 9.


Dietary supplements (which include vitamins, minerals, cofactors, herbal medications, and amino acids) are not considered over-the-counter drugs in the USA but rather food supplements. In 1994, the United States Congress, influenced by growing “consumerism” as well as strong manufacturer lobbying efforts, passed the Dietary Supplement and Health Education Act (DSHEA). This misguided act prevented adequate FDA oversight of these substances. Thus, DSHEA has allowed a variety of substances with pharmacologic activityif classified as dietary supplementsto be sold without a prescription or any FDA review of efficacy or safety prior to product marketing. Dietary supplements are governed under Current Good Manufacturing Practice in Manufacturing, Packaging or Holding Human Food (CGMP) regulations. Although administered by the FDA, CGMP regulations are often inadequate to ensure product purity, potency, and other variables such as accurate product identification and appropriate botanical harvesting. Therefore, much of the criticism regarding the dietary supplement industry involves a lack of product purity and variations in potency.


Many United States consumers have embraced the use of botanicals and other supplements as a “natural” approach to their health care. Unfortunately, misconceptions regarding safety and efficacy of the agents are common, and the fact that a substance can be called “natural” of course does not guarantee its safety. In fact, these products can be adulterated, misbranded, or contaminated either intentionally or unintentionally in a variety of ways. Furthermore, the doses recommended for active botanical substances may be much higher than those considered clinically safe. For example, the doses recommended for several Ma-huang preparations contain three to five times the medically recommended daily dose of the active ingredient, ephedrinedoses that impose significant risks for patients with cardiovascular disease.

Adverse effects have been documented for a variety of botanical medications. Unfortunately, chemical analysis is rarely performed on the products involved. This leads to uncertainty about whether the primary herb or an adulterant caused the adverse effect. In some cases, the chemical constituents of the herb can clearly lead to toxicity. Some of the herbs that should be used cautiously or not at all are listed in Table 65-1.




The three most widely used species of Echinacea are Echinacea purpurea, E pallida, and E angustifolia. The chemical constituents include flavonoids, lipophilic constituents (eg, alkamides, polyacetylenes), water-soluble polysaccharides, and water-soluble caffeoyl conjugates (eg, echinacoside, chicoric acid, caffeic acid). Within any marketed echinacea formulation, the relative amounts of these components are dependent upon the species used, the method of manufacture, and the plant parts used. The German Commission E has approved two formulations for clinical use: the fresh pressed juice of aerial parts of E purpurea and the alcoholic root extract of E pallida. E purpurea has been the most widely studied in clinical trials. Although the active constituents of echinacea are not completely known, chicoric acid from E purpurea and echinacoside from E pallida and E angustifolia, as well as alkamides and polysaccharides, are most often noted as having immune-modulating properties. Most commercial formulations, however, are not standardized for any particular constituent.

Pharmacologic Effects

The effect of echinacea on the immune system is controversial. Human studies using commercially marketed formulations of echinacea have shown increased phagocytosis but not immunostimulation. In vitro, however, E purpurea juice increased production of interleukin-1, -6, -10, and tumor necrosis factor- by human macrophages. Enhanced natural killer cell activity and antibody-dependent cellular toxicity was also observed with E purpurea extract in cell lines from both healthy and immunocompromised patients. Studies using the isolated purified polysaccharides from E purpurea have also shown cytokine activation. Polysaccharides by themselves, however, are unlikely to accurately reproduce the activity of the entire extract.

Certain echinacea constituents have demonstrated anti-inflammatory properties in vitro. Inhibition of cyclooxygenase, 5-lipoxygenase, and hyaluronidase may be involved. In animals, application of E purpurea prior to application of a topical irritant reduced both paw and ear edema. There are too few clinical trials in humans to warrant the use of echinacea in wound healing.

Some in vitro studies have reported weak antibacterial, antifungal, antiviral, and antioxidant activity with echinacea constituents. The applicability of these findings to clinical trials is discussed below.

Clinical Trials

Echinacea is most often used to enhance immune function in individuals who have colds and other respiratory tract infections. Older reviews and cold treatment trials reported favorable results for the aerial parts of E purpurea in reducing symptoms or time to recovery if the agent was administered within the first 24 hours of a cold. To date, however, most of these trials have contained multiple variables (eg, formulation, dose, duration) that make it difficult to make a clear therapeutic recommendation or ensure reproducible outcomes. At best, symptoms and duration may be reduced by about 25-30%. Recent trials investigating preparations of E angustifolia and combinations of echinacea containing E angustifolia for cold treatment, however, have failed to find a benefit. Echinacea has also been evaluated as a prophylactic agent in the prevention of upper respiratory tract infection in adults and as a treatment and prophylactic agent for colds in children. These trials have generally reported no effect.

Echinacea has been used investigationally to enhance hematologic recovery following chemotherapy. It has also been used as an adjunct in the treatment of urinary tract and vaginal fungal infections. These indications require further research before they can be accepted in clinical practice. E purpurea is ineffective in treating recurrent genital herpes.

Adverse Effects

Flu-like symptoms (eg, fever, shivering, headache, vomiting) have been reported following the intravenous use of echinacea extracts. Adverse effects with oral commercial formulations are minimal and most often include unpleasant taste, gastrointestinal upset, or central nervous system effects (eg, headache, dizziness). Allergic reactions such as rash, acute asthma, and anaphylaxis have been infrequently reported.

Drug Interactions  Precautions

Until the role of echinacea in immune modulation is better defined, this agent should be avoided in patients with immune deficiency disorders (eg, AIDS, cancer), autoimmune disorders (eg, multiple sclerosis, rheumatoid arthritis), and patients with tuberculosis. The German Commission E recommends limiting the chronic use of echinacea to no more than 8 weeks. While there are no reported drug interactions for echinacea, some preparations have a high alcohol content and should not be used with medications known to cause a disulfiram-like reaction. Theoretically echinacea should also be avoided in persons taking immunosuppressant medications (eg, organ transplant recipients).


Because of recent negative trials using E angustifolia for colds and a lack of clinical trials examining E pallida, only the dosing for E purpurea is provided here. E purpurea freshly pressed juice is given at a dosage of 6-9 mL/d in divided doses two to five times daily. Echinacea is generally taken at the first sign of a cold.



The pharmacologic activity of garlic involves a variety of organosulfur compounds. The most notable of these is allicin, which is responsible for the characteristic garlic odor.

Pharmacologic Effects

In vitro, allicin and related compounds inhibit HMG-CoA reductase, which is involved in cholesterol biosynthesis (see Chapter 35). Several clinical trials have investigated the lipid-lowering potential of garlic. Some have shown significant reductions in cholesterol and others no effect. The most recent meta-analysis suggested a minor (5%) reduction of total cholesterol that was insignificant when dietary controls were in place. Results of a study by the National Center of Complementary and Alternative Medicine (NCCAM) evaluating three different sources of garlic (fresh, powdered, and aged garlic extract) in adults with moderately elevated cholesterol are likely to be published in 2006 and may provide further insight into the efficacy of this botanical for this indication.

Clinical trials report antiplatelet effects (possibly through inhibition of thromboxane synthesis) following garlic ingestion and mixed effects on fibrinolytic activity. These effects in combination with antioxidant effects (eg, increased resistance to low-density lipoprotein oxidation) and reductions in total cholesterol may be beneficial in patients with atherosclerosis. In preliminary trials involving atherosclerotic patients, significant reductions in plaque volume were observed for patients taking garlic versus placebo.

Garlic constituents may affect blood vessel elasticity and blood pressure. Proposed mechanisms include opening of potassium channels in vascular smooth muscle, stimulation of nitric oxide synthesis, and inhibition of angiotensin-converting enzyme. Epidemiologic studies suggest that individuals chronically consuming low doses of garlic (averaging 460 mg/d) may have reductions in aortic stiffness. A meta-analysis of garlic’s antihypertensive properties revealed a mild effect with a 7.7 mm Hg decrease in systolic pressure and a 5 mm Hg decrease in diastolic pressure.

The effect of garlic on glucose homeostasis does not appear to be significant in persons with diabetes. Certain organosulfur constituents in garlic, however, have demonstrated hypoglycemic effects in nondiabetic animal models.

In vitro, allicin has demonstrated activity against some gram-positive and gram-negative bacteria as well as fungi (Candida albicans), protozoa (Entamoeba histolytica), and certain viruses. The primary mechanism involves the inhibition of thiol-containing enzymes needed by these microbes. The antimicrobial effect of garlic has not been extensively studied in clinical trials. Given the availability of effective prescription antimicrobials, the usefulness of garlic in this area appears limited.

In rodent studies, garlic inhibits procarcinogens for colon, esophageal, lung, breast, and stomach cancer, probably by detoxification of carcinogens and reduced carcinogen activation. The evidence for anticarcinogenic properties in vivo is largely epidemiologic. For example, certain populations with high dietary garlic consumption appear to have a reduced incidence of stomach cancer.

Adverse Effects

Following oral ingestion, adverse effects may include nausea (6%), hypotension (1.3%), allergy (1.1%), and bleeding (rare). Breath odor has been reported with an incidence of 20-40% at recommended doses using enteric-coated formulations. Contact dermatitis may occur with the handling of raw garlic.

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Drug Interactions  Precautions

Because of reported antiplatelet effects, patients using anticlotting medications (eg, warfarin, aspirin, ibuprofen) should use garlic cautiously. Additional monitoring of blood pressure and signs and symptoms of bleeding is warranted. Garlic may reduce the bioavailability of saquinavir, an antiviral protease inhibitor, but it does not appear to affect the bioavailability of ritonavir.


Products should be standardized to contain 1.3% alliin (the allicin precursor) or have an allicin-generating potential of 0.6%. Enteric-coated formulations are recommended to minimize degradation of the active substances. A daily dose of 600-900 mg/d of powdered garlic is most common. This is equivalent to one clove of raw garlic (2-4 g) per day.



Ginkgo biloba extract is prepared from the leaves of the ginkgo tree. The most common formulation is prepared by concentrating 50 parts of the crude leaf to prepare one part of extract. The active constituents in ginkgo are flavone glycosides and terpenoids (ie, ginkgolides A, B, C, J, and bilobalide).

Pharmacologic Effects

In animal models and some human studies, ginkgo has been shown to increase blood flow and reduce blood viscosity, thus enhancing tissue perfusion. Enhancement of endogenous nitric oxide (see Chapter 19) and antagonism of platelet-activating factor may be involved.

Ginkgo biloba has been studied for its effects on mild to moderate occlusive peripheral arterial disease. Randomized studies involving 120-160 mg of standardized ginkgo leaf extract (EGb761) for up to 6 months have generally reported significant improvements in pain-free walking distance as compared with placebo. Efficacy may be comparable to pentoxyfylline (see Chapter 20) for this indication. (It should be noted that physical conditioning is as effective as pentoxyfylline in improving walking distance.)

Antioxidant and radical-scavenging properties have been observed for the flavonoid fraction of ginkgo as well as some of the terpene constituents. In vitro, ginkgo has demonstrated superoxide dismutase-like activity and superoxide anion- and hydroxyl radical-scavenging properties. It has also demonstrated a protective effect in limiting free radical formation in animal models of ischemic injury and in reducing markers of oxidative stress in patients undergoing coronary artery bypass surgery.

In aged animal models, chronic administration of ginkgo for 3-4 weeks led to modifications in central nervous system receptors and neurotransmitters. Receptor densities increased for muscarinic, 2, and 5-HT1a receptors and decreased for  adrenoceptors. Increased serum levels of acetylcholine and norepinephrine and enhanced synaptosomal reuptake of serotonin have also been reported. Additional mechanisms that may be involved include reversible inhibition of monoamine (MAO) A and B, reduced corticosterone synthesis, inhibition of amyloid-beta fibril formation, and enhanced GABA levels.

Ginkgo is frequently used to treat cerebral insufficiency and dementia of the Alzheimer type. The term cerebral insufficiency, however, includes a variety of manifestations ranging from poor concentration and confusion to anxiety and depression as well as physical complaints such as hearing loss and headache. For this reason, studies evaluating cerebral insufficiency tend to be more inclusive and difficult to assess than trials evaluating dementia. A meta-analysis by the Cochrane Collaboration found that ginkgo showed promising evidence for improvement of cognitive function in patients with cognitive impairment and dementia. The duration of the largest of these studies was 1 year. Recent studies on the effects of ginkgo for memory enhancement in healthy nondemented elderly adults did not show a benefit with 6 weeks of use. Ginkgo is currently under investigation as a prophylactic agent for dementia of the Alzheimer type.

Ginkgo has been studied for its effects in allergic and asthmatic bronchoconstriction, erectile dysfunction, tinnitus and hearing loss, short-term memory loss in healthy nonelderly adults, and macular degeneration. In all of these conditions, the evidence is insufficient to warrant clinical use at this time.

Adverse Effects

Adverse effects have been reported with a frequency comparable to that of placebo. These include nausea, headache, stomach upset, diarrhea, allergy, anxiety, and insomnia. A few case reports noted bleeding complications in patients using ginkgo. In a few of these cases, the patients were also using either aspirin or warfarin.

Drug Interactions  Precautions

Ginkgo may have antiplatelet properties and should not be used in combination with antiplatelet or anticoagulant medications. A case of an enhanced sedative effect was reported when ginkgo was combined with trazodone. Seizures have been reported as a toxic effect of ginkgo, most likely related to seed contamination in the leaf formulations. Ginkgo seeds are epileptogenic. Ginkgo formulations should be avoided in individuals with preexisting seizure disorders.


Ginkgo biloba dried leaf extract should be standardized to contain 24% flavone glycosides and 6% terpene lactones. Products should be concentrated to a 50:1 ratio. The daily dose ranges from 120-240 mg of the dried extract in two or three divided doses. Onset of effect may require 2-4 weeks.



Ginseng botanical preparations may be derived from any of several species of the genus Panax. Of these, crude preparations or extracts of Panax ginseng, the Chinese or Korean variety, and P quinquefolium, the American variety, are most often available to consumers in the United States. The active principles appear to be a dozen or more triterpenoid saponin glycosides called ginsenosides or panaxosides. It is recommended that commercial P ginseng formulations be standardized to contain 4-7% ginsenosides.

Other plant materials are commonly sold under the name ginseng but are not from Panax species. These include Siberian ginseng (Eleutherococcus senticosus) and Brazilian ginseng (Pfaffia paniculata). Of these, Siberian ginseng is more widely available in the USA. Siberian ginseng contains eleutherosides but no ginsenosides. Currently, there is no recommended standardization for eleutheroside content in Siberian ginseng products.


An extensive literature exists on the potential pharmacologic effects of ginsenosides. Unfortunately, the studies differ widely in the species of Panax used, the ginsenosides studied, the degree of purification applied to the extracts, the animal species studied, and the measurements used to evaluate the responses. Some of the more commonly reported beneficial pharmacologic effects include modulation of immune function, ergogenic (“energizing”) activity, nootropic (“mind-enhancing”) activity, antioxidant activity, anti-inflammatory effects, antistress activity (ie, stimulation of pituitary-adrenocortical system), analgesia, vasoregulatory effects, antiplatelet activity, improved glucose homeostasis, and anticancer properties.

Clinical Trials

Ginseng is most often used to help improve physical and mental performance. Unfortunately, the clinical trials are of small sample size and report either an improvement in mental function and physical performance or no effect. Some randomized controlled trials evaluating “quality of life” have claimed significant benefits in some subscale measures of quality of life but rarely in overall composite scores using P ginseng. Better results have been observed with P quinquefolium in lowering postprandial glucose indices in subjects with and without diabetes. Newer trials have shown some immunomodulating benefits of P quinquefolium and P ginseng in preventing upper respiratory tract infections. Epidemiologic studies have suggested a reduction in several types of cancer with P ginseng. Systematic reviews, however, have generally failed to find conclusive evidence for the use of P ginseng for any particular condition. Until better clinical studies are published, no recommendation can be made regarding the use of P ginseng or P quinquefolium for any specific indication.

Adverse Effects

A variety of adverse effects have been reported. Weak estrogenic properties may cause the vaginal bleeding and mastalgia reported by some patients. Central nervous system stimulation (eg, insomnia, nervousness) and hypertension have been reported in patients using high doses (more than 3 g/d) of P ginseng. Methylxanthines found in the ginseng plant may contribute to this effect. The German Commission E lists high blood pressure as a contraindication to the use of Siberian ginseng but not P ginseng.

Drug Interactions  Precautions

Irritability, sleeplessness, and manic behavior have been reported in psychiatric patients using ginseng in combination with other medications (phenelzine, lithium, neuroleptics). Ginseng should be used cautiously in patients taking any psychiatric, estrogenic, or hypoglycemic medications. Ginseng has antiplatelet properties and should not be used in combination with warfarin. Similar to echinacea, cytokine stimulation has been observed for both P ginseng and P quinquefolium, necessitating cautious use in individuals who are immunocompromised, are taking immune stimulants or suppressants, or have autoimmune disorders.


The German Commission E recommends 1-2 g/d of crude P ginseng root or its equivalent. Two hundred milligrams of ginseng extract is equivalent to 1 g of the crude root. Ginsana has been used as a standardized extract in some clinical trials and is available in the USA. Dosing for Siberian ginseng is 2-3 g/d of the crude root.



The fruit and seeds of the milk thistle plant contain a lipophilic mixture of flavonolignans known as silymarin. Silymarin comprises 2-3% of the dried herb and is composed of three primary isomers, silybin (also known as silybinin or silibinin), silychristin (silichristin), and silydianin (silidianin). Silybin is the most prevalent and potent of the three isomers and accounts for about 50% of the silymarin complex. Products should be standardized to contain 70-80% silymarin.

Pharmacologic Effects

In animal models, milk thistle limits hepatic injury associated with a variety of toxins, including Amanita mushrooms, galactosamine, carbon tetrachloride, acetaminophen, radiation, cold ischemia, and ethanol. In vitro studies and some in vivo studies demonstrate that silymarin reduces lipid peroxidation, scavenges free radicals, and enhances glutathione and superoxide dismutase levels. This may contribute to membrane stabilization and reduce toxin entry.

Milk thistle appears to have anti-inflammatory properties. In vitro, silybin strongly and noncompetitively inhibits lipoxygenase and leukotriene formation. Inhibition of leukocyte migration has been observed in vivo and may be a factor when acute inflammation is present. Silymarin also inhibits tumor necrosis factor--mediated activation of nuclear factor kappa B (NF-B), which promotes inflammatory responses. One of the most unusual mechanisms claimed for milk thistle involves an increase in RNA polymerase I activity in nonmalignant hepatocytes but not in hepatoma or other malignant cell lines. By increasing this enzyme’s activity, enhanced protein synthesis and cellular regeneration may occur in diseased but not malignant cells. Milk thistle may have a role in hepatic fibrosis. In an animal model of cirrhosis, it reduced collagen accumulation, and in an in vitro model it reduced expression of the profibrogenic cytokine transforming growth factor-.

It has been suggested that milk thistle may be beneficial in the management of hypercholesterolemia and gallstones. A small trial in humans showed a reduction in bile saturation index and biliary cholesterol concentration. The latter may reflect a reduction in liver cholesterol synthesis. To date, however, there is insufficient evidence to warrant the use of milk thistle for these indications.

Preliminary in vitro and animal studies have been carried out with skin, lung, bladder, colon, tongue, breast, and prostate cancer cell lines. In murine models of skin cancer, silybinin and milk thistle reduced tumor initiation and promotion. It also inhibited cell growth and proliferation by inducing a G1 cell cycle arrest in cultured human breast and prostate cancer cell lines. However, the use of milk thistle in the treatment of cancer has not yet been adequately studied and should not be recommended to patients.

Clinical Trials

Milk thistle has been used to treat acute and chronic viral hepatitis, alcoholic liver disease, and toxin-induced liver injury in human patients. A recent systematic review of 13 randomized trials involving 915 patients with alcoholic liver disease or hepatitis B or C found no significant reductions in all-cause mortality, liver histology, or complications of liver disease. A significant reduction in liver-related mortality among all trials was documented, but not among trials of better design and controls. It was concluded that the effects of milk thistle in improving liver function or mortality from liver disease are currently poorly substantiated. Until additional well-designed clinical trials (possibly exploring higher doses) can be performed, a clinical effect can be neither supported nor ruled out.

Milk thistle has not been well studied in humans as an antidote following acute exposure to liver toxins. Parenteral silybin, however, is marketed and used in Europe as an antidote in Amanita phalloides mushroom poisoning, based on favorable outcomes reported in case-control studies.

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Adverse Effects

Milk thistle has rarely been reported to cause adverse effects when used at recommended dosage. In clinical trials, the incidence of adverse effects (eg, gastrointestinal upset, dermatologic, headaches) was comparable to that of placebo.

Drug Interactions, Precautions,  Dosing

There are no reported drug-drug interactions or precautions for milk thistle. Recommended dosage is 280-420 mg/d, calculated as silybin, in three divided doses.



St. John’s wort, also known as hypericum, contains a variety of constituents that may contribute to its pharmacologic activity. Hypericin, a marker of standardization for currently marketed products, was thought to be the primary antidepressant constituent. Recent attention has focused on hyperforin, but a combination of several compounds is probably involved. Commercial formulations are usually prepared by soaking the dried chopped flowers in methanol to create a hydroalcoholic extract that is then dried.

Pharmacologic Effects

The hypericin fraction was initially reported to have MAO-A and -B inhibitor properties. Later studies found that the concentration required for this inhibition was higher than that which could be achieved with recommended dosages. In vitro studies using the commercially formulated hydroalcoholic extract have shown inhibition of nerve terminal reuptake of serotonin, norepinephrine, and dopamine. While the hypericin constituent did not show reuptake inhibition for any of these systems, a concentrated hyperforin extract did. Chronic administration of the commercial extract has also been shown to significantly down-regulate the expression of cortical  adrenoceptors and up-regulate the expression of serotonin receptors (5-HT2) in a rodent model.

Other effects observed in vitro include opioid sigma receptor binding using the hypericin fraction and GABA receptor binding using the commercial extract. Interleukin-6 production is also reduced in the presence of the extract.

The most systematic review and meta-analysis, which involved 37 randomized controlled trials, demonstrated that St. John’s wort is more efficacious than placebo and as efficacious as some prescription antidepressants for mild to moderate depression. Efficacy for more severe depression, however, is still in question. Most trials used doses of St. John’s wort ranging from 900 mg/d (for mild to moderate depression) to 1800 mg/d (for severe depression) and lasted 4-8 weeks.

The hypericin constituent of St. John’s wort is photolabile and can be activated by exposure to certain wavelengths of visible or ultraviolet A light. Parenteral formulations of hypericin (photoactivated just before administration) have been used investigationally to treat HIV infection (given intravenously) and basal and squamous cell carcinoma (given by intralesional injection). In vitro, photoactivated hypericin inhibits a variety of enveloped and nonenveloped viruses as well as the growth of cells in some neoplastic tissues. Inhibition of protein kinase C and of singlet oxygen radical generation have been proposed as possible mechanisms. The latter could inhibit cell growth or cause cell apoptosis. These studies were carried out using the isolated hypericin constituent of St. John’s wort; the usual hydroalcoholic extract of St. John’s wort has not been studied for these indications and should not be recommended for patients with viral illness or cancer.

Adverse Effects

Photosensitization has been reported, and patients should be instructed to wear sunscreen while using this product. Hypomania, mania, and autonomic arousal have also been reported in patients using St. John’s wort.

Drug Interactions  Precautions

Inhibition of reuptake of various amine transmitters has been highlighted as a potential mechanism of action for St. John’s wort. Drugs with similar mechanisms (ie, antidepressants, stimulants) should be used cautiously or avoided in patients using St. John’s wort due to the risk of serotonin syndrome or MAO crisis (see Chapters 16 and 30). This herb may induce hepatic CYP enzymes (3A4, 2C9, 1A2) and the P-glycoprotein drug transporter. This has led to case reports of subtherapeutic levels of numerous drugs, including digoxin, birth control drugs (and subsequent pregnancy), cyclosporine, HIV protease and nonnucleoside reverse transcriptase inhibitors, warfarin, irinotecan, theophylline, and anticonvulsants.


The most common commercial formulation of St. John’s wort is the dried hydroalcoholic extract. Products should be standardized to 2-5% hyperforin, although most still bear the older standardized marker of 0.3% hypericin. The recommended dosing for mild to moderate depression is 900 mg of the dried extract per day in three divided doses. Onset of effect may take 2-4 weeks. Long-term benefits beyond 12 weeks have not been sufficiently studied.



The active constituents in saw palmetto berries are not well defined. Phytosterols (eg, -sitosterol), aliphatic alcohols, polyprenic compounds, and flavonoids are all present. Marketed preparations are lipophilic extracts that contain 85-95% fatty acids and sterols.

Pharmacologic Effects

Saw palmetto is most often used in the treatment of benign prostatic hyperplasia (BPH). Enzymatic conversion of testosterone to dihydrotestosterone (DHT) by 5-reductase is inhibited by saw palmetto in vitro. Specifically, saw palmetto shows a noncompetitive inhibition of both isotypes (I and II) of this enzyme, thereby reducing DHT production. In vitro, saw palmetto also inhibits the binding of DHT to androgen receptors. Additional effects that have been observed in vitro include inhibition of prostatic growth factors, blockade of 1 adrenoceptors, and inhibition of inflammatory mediators produced by the 5-lipoxygenase pathway.

The clinical pharmacology of saw palmetto in humans is not well defined. One week of treatment in healthy volunteers failed to influence 5-reductase activity, DHT concentration, or testosterone concentration. Six months of treatment in patients with benign prostatic hyperplasia also failed to affect prostate-specific antigen (PSA) levels, a marker that is typically reduced by enzymatic inhibition of 5-reductase. In contrast, other researchers have reported a reduction in epidermal growth factor, DHT levels, and estrogen expression after 3 months of treatment in patients with benign prostatic hyperplasia. Results of recent meta-analyses and reviews suggested that saw palmetto is significantly more effective than placebo in alleviating urologic symptoms (eg, peak flow, nocturia, international prostate symptom scores) associated with mild to moderate BPH. Saw palmetto, 320 mg/d, was also shown to have comparable efficacy to 5 mg/d of finasteride (a prescription 5-reductase inhibitor) and 0.4 mg/d of tamsulosin (a prescription -blocker) in clinical trials lasting 6 months and 1 year, respectively. In marked contrast, a recent well-controlled, double-blind 1-year study showed no significant effect of saw palmetto on symptoms or objective measures in moderate to severe BPH. The efficacy of saw palmetto in BPH beyond 5 years has not been studied.

Adverse Effects

Adverse effects are rare and reported with an incidence of 1-3%. The most common include gastrointestinal upset, hypertension, decreased libido, abdominal pain, impotence, back pain, urinary retention, and headache. In comparison to tamsulosin and finasteride, saw palmetto is less likely to affect sexual function (eg, ejaculation) in men.

Drug Interactions, Precautions,  Dosing

No drug-drug interactions have been reported for saw palmetto. Because saw palmetto has no effect on the PSA marker, it will not interfere with prostate cancer screening using this test. Recommended dosing of a standardized dried extract (containing 85-95% fatty acids and sterols) is 160 mg orally twice daily. Patients should be instructed that it may take 4-6 weeks for onset of clinical effects.




Coenzyme Q10, also known as CoQ, CoQ10, and ubiquinone, is found in the mitochondria of many organs, including the heart, kidney, and liver, and in skeletal muscle. After ingestion, the reduced form of coenzyme Q10, ubiquinol, predominates in the systemic circulation. Coenzyme Q10 is a potent antioxidant and may have a role in maintaining healthy muscle function, although the clinical significance of this effect is unknown. Reduced serum levels have been reported in Parkinson’s disease.

Clinical Uses

Various open label and controlled studies have identified small reductions in systolic and diastolic blood pressure of approximately 10 mm Hg following 10 weeks of therapy. Although this observation appears to be consistent, better designed studies are required.

Older studies suggested that coenzyme Q10 was effective as adjunctive therapy in the treatment of heart failure. Current research suggests that the supplement does not alter cardiac function (as determined with Swan-Ganz catheter measurements and echocardiography) in cardiomyopathy patients with class I, II, or III NY Heart Association status. Furthermore, patients with lower than normal endogenous coenzyme Q10 levels do not display subjective or objective improvements in heart failure assessments when given coenzyme Q10 supplements.

The effects of coenzyme Q10 on coronary artery disease and chronic stable angina are modest but appear promising. Double-blind, placebo-controlled trials have demonstrated that coenzyme Q10 supplementation improved a number of clinical measures in patients with a history of acute myocardial infarction (AMI). Improvements have been observed in lipoprotein a, high-density lipoprotein cholesterol, exercise tolerance, and time to development of ischemic changes on the electrocardiogram during stress tests. In addition, very small reductions in cardiac deaths and rate of reinfarction in patients with previous AMI were reported (absolute risk reduction 1.5%).

Coenzyme Q has been reported to slow the progression of early Parkinson’s disease when given at high dosage (300-1200 mg/d), although the time to requirement for levodopa treatment was not shortened. Another study indicated that migraine attacks were reduced in frequency at a dosage of 300 mg/d. No benefit was found in the treatment of amyotrophic lateral sclerosis or Huntington’s disease.

Adverse Effects

Coenzyme Q10 is well tolerated, rarely leading to any adverse effects at doses as high as 3000 mg/d. In clinical trials gastrointestinal upset, anorexia, and nausea have been reported. Cases of maculopapular rash and thrombocytopenia have very rarely been observed. Other rare adverse effects include irritability, dizziness, and headache.

Drug Interactions

Coenzyme Q10 shares a structural similarity with vitamin K, and an interaction has been observed between coenzyme Q10 and warfarin. Coenzyme Q10 supplements may decrease the effects of warfarin therapy. This combination should be avoided or very carefully monitored.

A reduction in endogenous coenzyme Q10 levels has been observed in patients beginning HMG-CoA reductase inhibitors. The clinical significance of this reduction is currently unknown, and the long-term effects of coenzyme Q10 supplementation in patients taking HMG-CoA reductase inhibitors has not been studied clinically. Anecdotal evidence has suggested that adding coenzyme Q10 to HMG-CoA reductase inhibitor therapy may help to prevent the rare adverse effect of myopathy, which can ultimately progress to rhabdomyolysis. Clinical trials are needed to confirm this effect.


As a dietary supplement, 30 mg of coenzyme Q10 is adequate to replace low endogenous levels. For neural or cardiac effects, typical doses are 100-600 mg/d given in two or three divided doses. These therapeutic doses increase endogenous levels to 2-3 mcg/mL (normal for healthy adults, 0.7-1 mcg/mL).




Glucosamine is found in human tissue, is a substrate for the production of articular cartilage, and also serves as a cartilage nutrient. Glucosamine is commercially derived from crabs and other crustaceans. As a dietary supplement, glucosamine is primarily used for pain associated with knee osteoarthritis.

Pharmacologic Effects  Clinical Uses

Endogenous glucosamine is used for the production of glycosaminoglycans and other proteoglycans in articular cartilage. In osteoarthritis, the rate of production of new cartilage is exceeded by the rate of degradation of existing cartilage. Supplementation with glucosamine is thought to increase the supply of the necessary glycosaminoglycan building blocks, leading to better maintenance and strengthening of existing cartilage.

Many clinical trials have been conducted on the effects of both oral and intra-articular administration of glucosamine. Early studies demonstrated significant improvements in overall mobility, range of motion, and strength in patients with osteoarthritis. Some recent evidence has shown mixed results, with both positive and negative trials. One meta-analysis found an overall moderate effect in knee osteoarthritis improvement, although study limitations may have overestimated treatment benefits. However, the most recent large double-blind trial, which compared glucosamine, chondroitin sulfate, the combination, and placebo, found no benefit for this therapy. It is possible that specific subgroups may benefit from glucosamine. More research is needed to better define the specific patient populations that stand to benefit from glucosamine.

Adverse Effects

Glucosamine is very well tolerated. In clinical trials, mild diarrhea and nausea were occasionally reported. Cross allergenicity in people with shellfish allergies is a potential concern; however, this is unlikely if the formulation has been adequately manufactured and purified.

Drug Interactions  Precautions

There are no known drug interactions with glucosamine.


The dosage used most often in clinical trials is 500 mg three times daily or 1500 mg once daily. Glucosamine does not have direct analgesic effects, and improvements, if any, may not be observed for 1-2 months. Although all salt forms of glucosamine (sulfate and hydrochloride) should dissolve and be available for absorption, there is some evidence that the sulfate formulation may be superior clinically.



Melatonin, a serotonin derivative produced by the pineal gland and some other tissues (see also Chapter 16), is believed to be responsible for regulating sleep-wake cycles. Release coincides with darkness; it typically begins around 9 PM and lasts until about 4 AM. Melatonin release is suppressed by daylight. Melatonin has also been studied for a number of other functions, including contraception, protection against endogenous oxidants, prevention of aging, and treatment of depression, HIV infection, and a variety of cancers. Currently, melatonin is most often administered to prevent jet lag and to induce sleep.

Pharmacologic Effects  Clinical Uses

Jet lag, a disturbance of the sleep-wake cycle, occurs when there is a disparity between the external time and the traveler’s endogenous circadian clock (internal time). The internal time regulates not only daily sleep rhythms but also body temperature and many metabolic systems. The synchronization of the circadian clock relies on light as the most potent “zeitgeber” (time giver).

Jet lag is especially common among frequent travelers and airplane cabin crews. Typical symptoms of jet lag may include daytime drowsiness, insomnia, frequent awakenings, and gastrointestinal upset. Clinical studies with administration of melatonin have reported subjective reduction in daytime fatigue, improved mood, and a quicker recovery time (return to normal sleep patterns, energy, and alertness). Unfortunately, many of these studies were characterized by inconsistencies in dosing, duration of therapy, and time of drug administration. In addition to melatonin, maximizing exposure to daylight on arrival at the new destination can aid in resetting the internal clock.

Melatonin has been studied in the treatment of various sleep disorders, including insomnia and delayed sleep-phase syndrome. It has been shown to improve sleep onset, duration, and quality when administered to healthy volunteers, suggesting a pharmacologic hypnotic effect. Melatonin has also been shown to increase rapid-eye-movement (REM) sleep.

Clinical studies in patients with sleep disorders have shown that oral melatonin supplementation may alter sleep architecture. Subjective improvements in sleep quality and improvements in sleep onset and sleep duration have been reported. However, the significance of these findings is impaired by many study limitations.

Patients older than 65 years of age tend to suffer from sleep maintenance insomnia; melatonin serum levels have been reported to be low in these patients. Elderly patients with sleep maintenance insomnia who received immediate-release and sustained-release melatonin had improved sleep onset time. They did not, however, experience an improvement in sleep maintenance or total sleep time.

Melatonin receptors have been identified in granulosa cell membranes, and significant amounts of melatonin have been detected in ovarian follicular fluid. Melatonin has been associated with midcycle suppression of luteinizing hormone surge and secretion. This may result in partial inhibition of ovulation. Nightly doses of melatonin (75-300 mg) given with a progestin through days 1-21 of the menstrual cycle resulted in lower mean luteinizing hormone levels. Therefore, melatonin should not be used by women who are pregnant or attempting to conceive. Furthermore, melatonin supplementation may decrease prolactin release in women and therefore should be used cautiously or not at all while nursing.

In healthy men, chronic melatonin administration ( 6 months) decreased sperm quality, possibly by aromatase inhibition in the testes. Until more is known, melatonin should not be used by couples who are actively trying to conceive.

Adverse Effects

Melatonin appears to be well tolerated and is often used in preference to over-the-counter “sleep-aid” drugs. Although melatonin is associated with few adverse effects, some next-day drowsiness has been reported as well as tachycardia, depression, vivid dreams, and headache. Sporadic case reports of movement disorders and psychoses have also appeared.

Drug Interactions

Melatonin drug interactions have not been formally studied. Various studies, however, suggest that melatonin concentrations are altered by a variety of drugs, including nonsteroidal anti-inflammatory drugs, antidepressants, -adrenoceptor agonists and antagonists, scopolamine, and sodium valproate. The relevance of these effects is unknown. Melatonin is metabolized by CYP450 1A2 and may interact with other drugs that either inhibit or induce the 1A2 isoenzyme.


The optimal timing and dose of melatonin have not been established. Current information suggests 5-8 mg of the immediate-release formulation given on the evening of departure and for 1-3 nights after arrival at the new destination. Exposure to daylight at the new time zone is also important to regulate the sleep-wake cycle.

Doses of 0.3-10 mg of the immediate-release formulation orally given once nightly have been tried. The lowest effective dose should be used first and may be repeated in 30 minutes up to a maximum of 10-20 mg. Sustained-release formulations may be used but currently do not appear to offer any advantages over the immediate-release formulations. Sustained-release formulations are also more costly.



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Coenzyme Q10

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Hodgson JM et al: Coenzyme Q10 improves blood pressure and glycaemic control: A controlled trial in subjects with type 2 diabetes. Eur J Clin Nutr 2002;56:1137.

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Schults CW et al: Effects of coenzyme Q10 in early Parkinson’s disease: Evidence of slowing of the functional decline. Arch Neurol 2002;59:1541.

Singh RB et al: Effect of coenzyme Q10 on risk of atherosclerosis in patients with recent myocardial infarction. Mol Cell Biochem 2003;246:75.


Goel V et al: Efficacy of a standardized echinacea preparation (EchinalinTM) for the treatment of the common cold: A randomized double-blind, placebo-controlled trial. J Clin Pharm Therapeutics 2004;29:75.

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Ackermann RT et al: Garlic shows promise for improving some cardiovascular risk factors. Arch Intern Med 2001;161:813.

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Predy GN et al: Efficacy of an extract of North American ginseng containing poly-furanosyl-pyranosyl-saccharides for preventing upper respiratory tract infections: A randomized controlled trial. Can Med Assoc J 2005;173:1043.

Yun TK: Experimental and epidemiological evidence on non-organ specific cancer preventative effect of Korean ginseng and identification of active compounds. Mutat Res 2003;523-524:63.


Clegg D et al: Glucosamine, chondroitin sulfate, and the two in combination for painful knee osteoarthritis. N Engl J Med 2006;354:795.

McAlindon T et al: Effectiveness of glucosamine for symptoms of knee osteoarthritis: Results from an internet-based randomized double-blind controlled trial. Am J Med 2004;117:643.

Milk Thistle

Jacobs BP et al: Milk thistle for the treatment of liver disease: A systematic review and meta-analysis. Am J Med 2002;113:506.

Rambaldi A et al: Milk thistle for alcoholic and/or hepatitis B or C virus liver diseases. Cochrane Database Syst Rev 2005;2:CD003620.

Singh RP et al: Mechanisms and preclinical efficacy of silibinin in preventing skin cancer. Eur J Cancer 2005;41:1969.

St. John’s Wort

Butterweck V: Mechanism of action of St. John’s wort in depression: What is known? CNS Drugs 2003;17:539.

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Saw Palmetto

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Petrie K et al: A double-blind trial of melatonin as a treatment for jet lag in international cabin crew. Biol Psychiatry 1993;33:526.

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