<John Lust, ND, D.B.M.  in "The Herb Book" 1987 states that Black Cohosh is in
addition to being an emmenogogue and antispasmodic, "a cardiac stimulant" and
"large doses can cause symptoms of poisoning. ">

Cheryl, you've asked a good question here as this aspect of black cohosh has
been an issue - don't know the book.

It is known that actein, a phytoconstituent of black cohosh, is hypotensive in
cats and rabbits, but not consistently in dogs.  In one human study, actein
was found to alter peripheral vasodilation in patients with peripheral
arterial disease, although blood pressure was unchanged.

 It can be misleading to consider only a purified compound's effects, when
wanting to know a herb's overall toxicity, however.  A plant may have a large
number of constituents with documented pharmacological effects, some opposing
each other, and some that would be expected to act in at least an additive
fashion.  While complicating scientific investigation by raising study to a
multivariate level, this situation does suggest why herbs with relatively
toxic components can show few side effects or toxicity effects in humans (
Duke's thinking here).

Studies of whole plant extracts are probably more reflective of clinical
situation.  Rats fed almost a gram/day of standardized extract for 26 weeks
had no obvious chemical or organ toxicities ( 1991 study).  In human studies
with the fluid extract, up to 890 mg/day produced no toxic effects.

Overdoses have been reported to produce nausea, vomiting, dizziness, sweating,
headache and may reduce pulse rate.  A related species, used in Traditional
Chinese Medicine ( shengma) can produce vertigo, severe headache, slow pulse
and "collapse".

Commission E suggested that use of black cohosh be limited to 6 months, due to
the lack of toxicity studies at the time of their report.  Use of black cohosh
in early pregnancy has always been contraindicated as it can induce
abortion/act as an emmenogogue ( this term describes a herb's ability to
induce a late period which may actually mean in some cases, to abort an early
pregnancy).

Studies of intestinal and uterine stimulation vary in results, depending on
the animal studied, whether pregnant uterus strips were used, and the species
of Cimicifuga used ( black cohosh or shengma).  All could bear repeating.

Regards,
Sheila Humphrey
BSc  RN  IBCLC
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