4 Echinacea has no direct bacteriocidal nor bacteriostatic properties. Several clinical trials have evaluated the efficacy of echinacea root extract for the prophylaxis and treatment of upper respiratory tract symptoms. Unfortunately the studies had methodology flaws and lacked clear diagnostic criteria and standardized dosing regimens. Adverse effects of and drug interactions with echinacea are unknown. Because echinacea can act as a potent nonspecific stimulator of the immune system, it should not be used for more than 6-8 weeks.
More research is necessary to fully assess the therapeutic potential of echinacea.
St. John's Wort St. John's wort is a perennial herb that is native to Europe and the United States. Although St. John's wort has antibacterial, antidepressant, and antiviral action, its main use is for the treatment of depression. Hypericin inhibits monoamine oxidase and the reuptake of serotonin, norepinephrine, and dopamine and binds to GABA receptors in vitro . Serum concentrations of hypericin peak approximately 5 hours after oral administration and reach steady-state in 4 days. The half-life of hypericin is approximately 25 hours.