ReviewsHarmless Herbs? A Review of the Recent Literature
Section snippets
Allergic Reactions
Herbal preparations can lead to hypersensitivity reactions [8]. Reactions can vary from a transient dermatitis to anaphylactic shock (Table 1). Royal jelly has been repeatedly linked with severe bronchospasm [8] and the alleged aphrodisiac yohimbine has been associated with an allergic reaction culminating in a lupus-like syndrome [9]. Other recent reports demonstrate the allergic potential of camphor [10] and a mixture of lavender, jasmin, and rosewood used in the form of aromatherapy [11].
Toxic Reactions
Many, if not most, medicinal plants contain flavonoids; over 100 such herbal preparations are on the European market. This family of compounds has been associated with several beneficial effects, such as antioxidative activity or reduction in vascular permeability. However, recent reports suggest that adverse reactions such as hemolytic anemia [12], chronic diarrhea [13], severe nephropathy [14], and colitis [15] can be associated with their use. In some of these cases, causality has been
Adverse Effects Related to the Desired Pharmacological Actions
A general deterioration in the conditions of schizophrenic patients, including symptoms of irritability, activity, and sleep disturbances was noticed after these patients had smoked ginseng cigarettes [48]. Discontinuation of this habit resulted in clinical improvement. One woman with a history of depression started taking ginseng tablets (1 per day) in addition to her antidepressants. Four days later she became overtly manic and had to be admitted to the hospital. After discontinuation of the
Mutagenic Effects
Anthranoid laxatives such as aloe, cascara, frangula, and rhubarb senna are commonly used and generally considered to be safe. However, the long-term use (10–30 years) of these drugs may be a risk factor for colorectal cancer [60]. In patients with colorectal carcinoma, the prevalence of pseudo-melanosis coli (typically caused by chronic laxative use) was 18.6%, while in cancer-free patients it was 6.9%. This potentially important finding needs confirmation from other studies, as the
Drug Interactions
The interactions of phytomedicines with prescription indications are underresearched. An inactivation or an enhancement of activity is possible [63]. For example, concomitant administration of phenytoin and the Ayurvedic (traditional Indian) remedy shankhapushpi has also been reported to have led to a reduction in serum phenytoin concentration, resulting in a loss of seizure control [64].
On the other hand, grapefruit juice ingestion elevates serum concentrations of cyclosporin, calcium-channel
Contamination
The lack of regulation in the area of herbal remedies may lead to contamination, which has repeatedly been a problem with Ayurvedic medicines. Lead poisoning has been described 68, 69, 70. Furthermore, some Ayurvedic preparations contain arsenic and other highly toxic substances as medicinal agents 71, 72. A British poison information center identified 5 such cases during a 7-year observation period. The preparations concerned contained lead (up to 60% lead by weight) zinc, mercury, arsenic,
Mistaken Plants
False authentication can be another problem with plant-derived medicines. This can happen inadvertently or be done deliberately to save money. An example of the former is the occurrence of fibrosing interstitial nephritis in individuals in Germany and France following the administration of a slimming aid; in this preparation the Chinese drug “Fangji” was substituted by “Guang fangji,” which contains nephrotoxic aristolochic acids 27, 29, 92, 93. An example of the latter scenario is an alleged
Incidence of Adverse Effects
One group of investigators retrospectively studied all 2,695 patients admitted to a Taiwan department of medicine during a 10-month period. Four percent of these patients were admitted because of drug-related problems; herbal remedies ranked third among the categories of medicines responsible for causing adverse effects [96]. A case-control study from the Philippines identified herbal medicine use as one of the main risk factors for nasopharyngeal carcinoma [97]. Another study, involving 1,701
Comparative Safety
Are botanical drugs more or less safe than synthetic medications? Hypericum perforatum seems to be as effective as standard antidepressants for mild to moderate depression, but is associated with significantly fewer adverse effects 103, 104. Similarly, two different herbal expectorant and secretolytic mixtures have been shown to be associated with fewer adverse effects than synthetic counterparts of comparable efficacy 105, 106.
In a large (n = 1,098) randomized clinical trial comparing a plant
Comment
Not all that is natural is harmless. Table 2 however, lists some popular plants commonly thought to be free of serious adverse effects. By contrast, several herbs seem likely to cause adverse effects (Table 3). Common adulterants are presented in Table 4.
Traditional use is no guarantee for safety. In particular, rare adverse effects, delayed effects (eg, mutagenicity), or effects that require long-term use may fail to be identified through the “test of time” [111]. Historical use can be
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