- 1 Clinical Use
- 2 Other Uses
Clinical trials using echinacea have used various preparations, such as topical applications, homeopathic preparations, injectable forms and oral dose forms, characteristics that should be noted when reviewing the data available. Overall, the majority of clinical studies performed in Europe have involved a commercial product known as Echinacin (Madaus, Germany), which contains the fresh-pressed leaf juice of Echinacea purpurea stabilised in ethanol.
UPPER RESPIRATORY TRACT INFECTIONS
Overall, clinical studies support the use of echinacea in URTIs, such as bacterial sinusitis, common cold, influenza-like viral infections and streptococcal throat. Evidence is strongest for use of echinacea in adults as an acute treatment; however, results in children have been disappointing.
A 1999 review of 13 clinical trials consisting of 9 treatment studies and 4 prevention studies concluded that 8 of 9 treatment trials produced positive results whereas 3 of 4 prevention trials suggested modest effects. In other words, current evidence is stronger for supporting the use of echinacea as acute treatment in URTIs than as prophylactic treatment. In 2000, a Cochrane review was published that had assessed the evidence available from 16 clinical trials (8 treatment and 8 prevention) involving a total of 3396 subjects, and it concluded that some echinacea preparations may be better than placebo, with a majority of studies reporting favourable effects. Unfortunately, due to variations in the type of echinacea preparations tested, it is still difficult to confidently determine which one is superior.
Since 2000, numerous other randomised double-blind studies have been published, with varied results.
Schulten et al (2001) recruited 80 adults experiencing the first signs of a cold and randomly assigned treatment with Echinacea purpurea (Echinacin, EC31J0) or placebo. The results revealed that treatment with echinacea shortened the duration of illness by 3 days compared with placebo and was well tolerated. Barrett et al (2002) used a very different echinacea product, an encapsulated mixture of unrefined Echinacea purpurea herb (25%) and root (25%) and Echinacea angustifolia root (50%). One hundred and forty-eight students with recent-onset colds took either placebo or echinacea capsules in 1 g doses six times on the first day, then three times on each subsequent day for a maximum of 10 days. The results did not produce a statistically significant treatment effect. No significant effects on total cold symptom scores, mean individual symptoms or time to resolution of symptoms were observed in a double-blind, placebo-controlled trial of 128 subjects conducted by Yale and Liu (2004) using a standardised preparation of Echinacea purpurea (freeze-dried pressed juice of the aerial portion). Subjects were enrolled within 24 hours of cold symptom onset and given 100 mg three times daily of active treatment or placebo. In contrast, a double-blind, placebo-controlled trial of 282 adults, which used a highly standardised formulation of freshly harvested Echinacea purpurea, found that it significantly reduced the total daily symptom scores by 23% compared to placebo. That study used Echinacea purpurea containing alkamides, cichoric acid, and polysaccha rides at concentrations of 0.25, 2.5, and 25 mg/mL, respectively and commercially available as Echinilin (Natural Factors Nutritional Products, Inc., Vancouver, BC, Canada). Subjects were instructed to start treatment at the onset of the first symptom related to a cold, consuming 10 doses the first day and 4 doses per day on subsequent days for 7 days.
A crucial factor in the investigation of any cold treatment is the time of treatment initiation. For best effects, treatment must be commenced at the first signs of infection, because later use is less likely to induce benefits. With regard to echinacea research, the time of initiation has varied between studies and is one possible explanation for the contradictory results obtained. Variations in the product’s chemical composition, the clinical setting and study populations are further confounding variables. Between 2000 and 2005, three studies have used artificial rhinovirus inoculation as a means of standardising ‘time to treatment initiation’, together with standardised echinacea extracts. The two earlier studies used Echinacea purpurea, whereas the most recent one used two different concentrations of an alcoholic extract of Echinacea angustifolia. According to these studies, echinacea inhibited the onset and severity of symptoms; however, this was not significantly superior to placebo.
In response to these negative findings, Schoop et al (2006) conducted a meta-analysis to determine whether the results were a consequence of inadequate efficacy or inadequate sample size. Based on the analysis, the likelihood of experiencing a clinical cold was 55% higher with placebo than with echinacea treatment; however, there was no significant difference between groups for total symptom scores.
A recently published Cochrane systematic review analysed results from 16 randomised, double-blind studies, only 5 of which had been included in a previous Cochrane review. Studies that investigated the effectiveness of combination echinacea products or Echinacea purpurea preparations compared to placebo in the prevention of experimentally induced rhinovirus infections were not included. The authors concluded that overall assessment was difficult to make because of the great heterogeneity of preparations tested and variability of trial approaches and methods for cold assessment. Even so, they concluded that there is some evidence that preparations based on the aerial parts of Echinacea purpurea might be effective for the early treatment of colds in adults, although results are not completely consistent. Beneficial effects of other echinacea preparations, and their use for preventative purposes, might exist, but have not been shown in independently replicated, rigorous randomised trials.
It is hoped that future research will include full disclosure of the chemical analysis of the echinacea preparation being tested. Systematic reviews will then be able to use this information to separately assess the effects of each echinacea species, rather than combining them under the umbrella term of ‘Echinacea’.
Four randomised studies published after 2000 were conducted with children and generally produced disappointing results. Taylor et al (2003) studied the effects of Echinacea purpurea (dried pressed juice of the aerial portions) mixed into a syrup in healthy children aged 2-11 -years-old who were advised to start treatment at the onset of cold symptoms and continue for a maximum of 10 days or until symptoms resolved. Treatment with Echinacea purpurea failed to reduce the duration of the URTI or severity of symptoms compared with placebo. There was no difference in the rate of adverse events reported by both groups, although rash occurred in 7.1% of children using echinacea compared with 2.7% with placebo. Spasov et al (2004) compared the effects of Echinacea purpurea extract to placebo and a herbal combination treatment (Kan Jang) in 130 children aged between 4 and 11 years over a period of 10 days. They found that treatment with Kan Jang was more effective than echinacea for reducing symptom severity and reducing symptom duration when started at the early stage of uncomplicated common colds. In contrast, Echinacea purpurea appeared to reduce the incidence of subsequent URTIs in a double-blind, placebo-controlled study of 401 children.
A combination product was investigated in the study by Cohen et al (2004), which involved 430 children aged 1-5 years. The preparation (Chizukit, Hadas Corp., Israel) contained 50 mg/mL of echinacea (aerial parts of Echinacea purpurea and roots of Echinacea angustifolia), 50 mg/mL of propolis and 10 mg/mL of vitamin C and was administered twice daily for 12 weeks. Active treatment resulted in a significant reduction in illness episodes (55% reduction), number of episodes per child (50% reduction) and number of days with fever per child (2.1 vs 5.4; 62% reduction). The total number of illness days and duration of individual episodes were also significantly lower in the treatment group.
Commission E approves the use of Echinacea purpurea herb as an immune system support in cases of respiratory and lower urinary tract infection, and Echinacea pallida root as supportive treatment in influenza-like infections.
Clinical note — Common cold symptoms: what is usual?
The pathogenesis of the common cold involves a complex interplay between replicating viruses and the host’s inflammatory response. The onset of cold symptoms after viral incubation varies considerably and depends on the causative virus. In experimental rhinovirus infections, the onset of symptoms has been reported to occur as soon as 10-12 hours after intranasal inoculation. Generally, the severity of the symptoms increases rapidly, peaks within 2-3 days after infection, and decreases soon after. The mean duration of the common cold is 7-10 days, but in a proportion of patients some symptoms can still be present after 3 weeks. Symptoms typically start with a sore throat, which is soon accompanied by nasal stuffiness and discharge, sneezing and cough. The soreness of the throat usually disappears quickly, whereas the initial watery rhinorrhoea becomes thicker and more purulent over time and can be accompanied by fever, most usually in children. Other symptoms associated with the cold syndrome include hoarseness, headache, malaise and lethargy.
Several uncontrolled clinical studies support the topical use of echinacea to enhance wound healing. A trial involving 4598 people investigated the effects of a preparation consisting of the juice of the aerial parts of Echinacea purpurea on various wounds, burns, skin infections and inflammatory skin conditions. Topical application of echinacea produced a 85% overall success rate, and the key constituent responsible for enhancing wound healing appears to be echinacoside.
Commission E approves the external use of Echinacea purpurea herb for poorly healing wounds and chronic ulcerations.
A prospective, double-blind, placebo-controlled crossover trial conducted over 1 year investigated the effects of an extract of the plant and root of Echinacea purpurea (Echinaforce 800 mg twice daily) on the incidence and severity of genital herpes outbreaks in 50 patients. The study found no statistically significant benefit compared with placebo after 6 months of therapy.
REDUCING CHEMOTHERAPY SIDE-EFFECTS
Results from a small, open, prospective study of subjects with advanced gastric cancer suggests that intravenous administration of a polysaccharide fraction isolated from Echinacea purpurea may be effective in reducing chemotherapy-induced leucopenia. Test subjects had advanced gastric cancer and were undergoing palliative chemotherapy with etoposide, leucovorin and 5-fluorouracil. The median number of leukocytes 14-16 days after chemotherapy was 3630/microL (range 1470-5770) in the patients receiving herbal treatment compared with 2370/microL (870-3950) in the patients of the historical control group (P = 0.01 5).
Equivocal evidence exists for the use of echinacea in radiation-induced leucopenia, according to a small number of randomised studies (Ulbricht & Basch 2006). The product tested was Esberitox, which contains ethanolic extracts of three herbs, including root of echinacea.
The herb is used to treat recurrent candidiasis, chiefly because of its antifungal and immunostimulant properties. Controlled studies are unavailable to determine effectiveness in this condition.
Echinacea has also been used to treat UTI, allergies, acne and abscesses, and as adjunctive therapy in cancer. It has also been used to prevent exercise-induced immunosuppression. In practice, it is prescribed with other herbs to treat common infections and to prevent infections generally.