ECHINACEA (E. PURPUREA, E. PALLIDA,
II. ECHINACEA (E. PURPUREA, E. PALLIDA,
E. AUGUSTIFOLIA) Today oral HMPs of echinacea are used predominantly for the prevention
and treatment of the common cold. A systematic review(8) included 16 RCTs with a total of 3396 participants. Five of the RCTs were placebo-controlled. Their methodological quality was variable but, on average, satisfactory. Results suggested that some echinacea preparations have an effect over and above that of placebo. Unfortunately, the trials were highly heterogeneous in many respects. No clear evidence emerged for one echinacea species being
Systematic Reviews of HMPs 849
superior to another. The authors of the systematic reviewconcluded that ‘‘there is, to date, insufficient evidence to recommend a specific Echinacea
product, or Echinacea preparation, in the treatment or prevention of the common cold’’ (8).
No systematic reviewof the safety of echinacea has yet been published. Fewadverse effects are on record. The most frequent ones relate to allergic reactions, which can occasionally be severe (anaphylactic shock) but are probably rare. As an immunostimulant, echinacea could theoretically de- crease the effects of immunosuppressants (7), but no case reports have been published where this has resulted in clinical problems.
Weighing the known risks against the benefits, it is concluded that some encouraging, albeit not compelling, evidence supports the use of echinacea HMPs for the treatment and prevention of the common cold. Its use seems most promising in the very early stages of the condition. In viewof its apparent safety, echinacea seems worthy of further research. To date the evidence is, however, not strong enough to recommend any echinacea HMP for routine use.
III. GARLIC (ALLIUM SATIVUM ) Traditionally garlic has been used for a wide range of conditions, e.g., the
common cold and other infections. Today, the main indication for garlic is hypercholesterolemia. A recent meta-analysis (9) included 13 placebo-con- trolled, double-blind RCTs with a total of 806 patients with hypercholester- olemia. The methodological quality of these studies was good (Jadad score 3–5). The results of the meta-analysis demonstrated a weighted mean difference of
25.6 to 5.7). For the most rigorous RCTs, the effect size was only
15.7 mg/dL (95% CI =
9.4 mg/dL and not any longer statistically significant. Our overall conclusion therefore was ‘‘garlic is superior to
placebo . . .but the effect is modest and of debatable clinical relevance’’ (9). No systematic reviewof the safety of garlic is currently available. The most frequent adverse effects are mild and transient; they include body odor, allergic reactions, nausea, heartburn, and flatulence. Garlic has antiplatelet activity and can therefore increase the effect of anticoagulants, which, in rare cases, has been associated with bleeding. For the same reason, it seems prudent to discontinue garlic medication several days before major surgery (7).
Despite the relatively small effect on total cholesterol the benefits of garlic may well outweigh its risk. This is true particularly because garlic has a range of further beneficial actions on the cardiovascular system, including effects on blood pressure, coagulation factors, and arterial compliance (7).
850 Ernst
IV. GINKGO (GINKGO BILOBA) Ginkgo is used for a range of indications, most importantly perhaps for
vascular dementia and Alzheimer’s disease. A systematic review(10) included nine double-blind RCTs with a total of 606 patients suffering from dementia. The methodological quality of these studies was on average good (Jadad score 3–5). The dosage regimen varied by more than 100%. All but one of the nine trials yielded positive findings, and our overall judgment was therefore optimistic: ‘‘findings are encouraging and warrant independent, large scale confirmatory and comparative trials’’ (10). The question whether ginkgo enhances cognitive function in healthy subjects where it is not impaired, is still controversial. Both positive and negative answers have so far been provided by RCTs.
No systematic reviewof the safety of ginkgo has yet been published. Adverse effects are rare, usually transient, and mild; they include gastroin- testinal disturbances, diarrhea, vomiting, allergic reactions, pruritus, head- ache, dizziness, and nosebleeds. Ginkgo also has antiplatelet effects and therefore the same cautions apply as for garlic (7).
On balance, this collective evidence suggests that the risk-benefit profile of ginkgo is encouraging. There are fewrisks with proper use and the potential benefit for dementia patients is substantial.