Metabolife 356 Associated With Increased Cardiac Risk
Peggy Peck
Nov. 11, 2003 (Orlando) — In a small study of healthy
volunteers, a single Metabolife 356 tablet was associated
with a 24 millisecond increase in QTc interval on electrocardiogram,
an increase that investigators said was associated with a
3.5-fold increase in risk for torsade de pointes, according
to results presented here Nov. 9 at the American Heart Association
(AHA) Scientific Sessions.
Discussing his results in an AHA press conference, Brian
F. McBride, PharmD, from Hartford Hospital, Division of Cardiology
and Drug Information, University of Connecticut School of
Pharmacy, said the increase in QTc interval was consistent
"at one, three, and five hours." Moreover, a single
Metabolife tablet — which is just a third of the recommended
daily dose — also significantly increased both systolic
and diastolic blood pressure.
Metabolife 356 currently "controls about 49% of the
world market in diet supplements," McBride said. Metabolife
356 contains ephedra as well as 17 other ingredients and although
other studies have suggested an increased cardiac event risk
associated with ephedra, McBride said, "we don't really
know if ephedra is responsible for these changes; it is possible
that another ingredient is responsible." He suggested
"safety testing all ingredients to identify true risk."
Metabolife spokesperson Jan Strode told Medscape, "While
we haven’t reviewed the study yet, all the ephedra studies
we have show no link between the herb and serious health effects.
We continue to believe that our products are safe and effective
when used as directed on the package."
In McBride's study, 15 healthy volunteers, aged 27 ±
3 years, 56% of whom were male, were randomized in a crossover
fashion to receive one tablet of Metabolife 356 or matching
placebo. Blood pressure, systemic vascular resistance, cardiac
output, heart rate, and stroke volume evaluations (BioZ monitor;
San Diego, California) were taken at baseline and at one,
three, and five hours postdosing. Evaluations were performed
at the same time of day to minimize circadian variation and
there was a one-week washout period between study phases.
Changes in systolic blood pressure from baseline were 10.00,
7.85, and 15.57 mm Hg higher at one, three, and five hours,
respectively, in the Metabolife 356 group compared with the
placebo group (P = .0029, P = .0105, P = .0107, respectively).
Changes in diastolic blood pressure from baseline were 5.26,
6.66, and 2.37 mm Hg higher at one, three, and five hours,
respectively, in the Metabolife 356 group compared with the
placebo group (P = .0301, P = .0331, P = .1483, respectively).
Changes in systemic vascular resistance from baseline were
94.41, 121.27, and 53.49 (dyne*sec)/cm5 higher at one, three,
and five hours, respectively, in the Metabolife 356 group
compared with placebo (P = .0106, P = .00587, P = .0736, respectively).
James J. Ferguson III, MD, FACC, associate director of clinical
cardiology research at The Heart Institute in Houston, Texas,
told Medscape that "I find these results interesting,
but I don't think it means that we would ban Metabolife. I
do think it indicates the need to test Metabolife [and] all
these nutraceuticals for safety. I think safety testing of
all ingredients is necessary." Dr. Ferguson was not involved
in the study.
McBride told Medscape that he is not advocating a Metabolife
ban, but he does support "doing the same type of safety
testing in these products that the [Food and Drug Administration]
requires for pharmaceuticals."
In addition, he noted that it is impossible to determine
if the results associated with a single dose would "worsen
or improve with continued use." But coauthor Jeffrey
Kluger, MD, told Medscape that the results seen with a single
dose of pharmaceuticals "are not attenuated with time.
So the single dose response [seen with Metabolife] does, in
my opinion, predict long-term outcome."
AHA 2003 Scientific Sessions: Abstract 3540. Presented Nov.
12, 2003.
Reviewed by Gary D. Vogin, MD
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