"San Francisco Ecstasy Conference Generates Heat But Also Light" --DRCNet, 2/9/01
Comments from Rick Doblin:
"The section where I'm quoted as saying that George Ricaurte's presentation on
MDMA neurotoxicity was misleading has to do with slides he showed, one of a
primate brain before MDMA with lots of serotonin neurons and nerve terminals
and one of a primate brain after MDMA with virtually no serotonin neurons and
nerve terminals. George indicated that the depletions shown were similar
throughout the brain. Though he didn't explicitly say, the slides were from
animals who received MDMA by injection twice a day for four days in a row, in
the amount of 20 mg/kg or more per injection. (Injection is twice as
neurotoxic as oral administration).
"George's discussion that followed highlighted his concern that a single 5
mg/kg oral dose of MDMA was likely to be neurotoxic in humans, when using a
standard formula for interspecies scaling to compare the likely effects of
doses between different species. The implication that was left was that the 5
mg/kg dose produced the sorts of depletions shown in the slides. However, the
5 mg/kg single oral dose produces no neurotoxicity in almost all the brain
regions studied. There were serotonin reductions after two weeks in only two
brain regions, with minor reductions that in no way resembled what was shown
on the slides. A recent letter in the scientific journal,
Neuropsychopharmacolgy, by two esteemed neuroscientists even questioned
Ricaurte's conclusion that a single oral dose of 5 mg/kg is neurotoxic. The
accuracy of the interspecies scaling formula in translating doses in
non-human primates to human doses has also been challenged on scientific
grounds relating to differences in metabolism of MDMA between non-human
primates and humans. Preliminary, unpublished research in Switzerland using
PET studies have shown that a single oral dose of 1.7 mg/kg does not reduce
serotonin levels. Nevertheless, it is still possible that a standard oral d
ose of MDMA in humans taken in a rave/dance context may reduce serotonin
levels to some degree. What is misleading is the impression that a standard
oral dose of MDMA may reduce serotonin levels that resemble what was seen in
the slides."
-- Rick Doblin
Back to the Media Page
|