Harmful effects raise concerns over long-term use of
nicotine therapy, but not short-course replacement
HARMFUL effects of nicotine, in the absence of tobacco,
have been demonstrated in a study published in Nature Medicine
this week (2001;7:833). However, the relevance of the work to smokers
using nicotine replacement therapy (NRT) to help them stop has been questioned.
Dr Mary Berrington, science information manager
for the Cancer Research Campaign, said: “This is interesting early work
but there is no evidence that it is of any relevance to people using short-term
nicotine replacement therapy to help them stop smoking.”
Dr Christopher Heeschen and colleagues, of the division
of cardiovascular medicine, Stanford University, California conducted
the study to test the effects of nicotine on a number of different disease
states in animal and cell-culture models.
They found that, in the absence of smoking, nicotine
stimulates the growth of blood vessels in a number of disease states,
including inflammation, ischaemia, cancer and atherosclerosis. They also
showed that nicotine enhances the angiogenic response to these conditions
and that it promotes atherosclerosis and tumour growth.
The researchers suggest several potential mechanisms
by which nicotine might enhance angiogenesis in vivo, including
the stimulation of endothelial processes via nicotinic acetylcholine receptors.
They note that the effects of nicotine were mediated at “concentrations
that are pathophysiologically relevant” although they propose that nicotine
stimulates angiogenesis only in pathological not physiological settings.
They say that their findings could have implications
for therapeutic uses of nicotine although their concerns relate mainly
to chronic uses of nicotine rather than to short courses of nicotine replacement
therapy (NRT). They note that studies of transdermal nicotine use did
not increase ischaemic events and add that this might be because the course
of NRT was brief or that patients stopped using tobacco at the same time.
However, the researchers caution that long-term nicotine therapy, such
as that being considered in some neurological disorders, would have to
take into account its harmful effects.
Pharmacia, the manufacturer of Nicorette products,
said: “The health risks suggested by this research are vastly overshadowed
by the severity and scale of the proven death and damage caused by tobacco.”
Back to Top
|
