Shows How Cocaine
Boosts Blood Pressure
NEW YORK (Reuters Health) - Researchers in Texas report that
they have determined the mechanism by which cocaine can cause
a person's blood pressure to skyrocket, leading to a potentially
fatal condition known as hypertensive crisis.
The findings, they say, could lead to more effective treatment of
hypertensive crisis and other health emergencies brought on by cocaine
Although many users may not be aware of the illicit drug's harmful
effects, cocaine abuse is a major cause of cardiovascular emergencies
including irregular heartbeat, heart attack and extreme high blood
pressure. Experts estimate that over 30 million Americans have
tried cocaine, and that 5 million are regular users.
Previous studies using tissue from rodents have suggested that
cocaine prevents the body from reabsorbing the nerve chemical
norepinephrine, which causes the blood vessels to narrow and thus
boosts blood pressure. But some scientists believe this explanation
is incomplete, as there is little evidence to support it from
studies in live animals or humans.
To investigate, lead author Dr. Meryem Tuncel of the University
of Texas Southwestern Research Medical Center in Dallas and her
team studied medically approved doses of cocaine in 15 otherwise
healthy people who had never used the drug.
The participants were given two different dosages of cocaine,
0.15 milligrams or 15 milligrams, either via infusion into a forearm
vein or in nose drops, according to the report in the March 5th
issue of Circulation: Journal of the American Heart Association.
After each dosing, the researchers measured blood pressure,
blood flow in the forearm and blood concentrations of norepinephrine.
The investigators found that when cocaine is given directly
into an artery, it does indeed cause blood vessels to constrict,
as was seen in the rodent tissue studies.
"However, when cocaine is given through the nose, it causes
dilation, rather than constriction of the blood vessels," senior
study author Dr. Wanpen Vongpatanasin said in a prepared statement.
In this instance, "cocaine increases blood pressure by stimulation
of the heart to cause rapid heartbeat and increased cardiac output.
This elevation in blood pressure, if severe or persistent, can
lead to damage of multiple vital organs such as heart, brain and
kidney," the researcher noted.
"Now that we know the mechanisms involved in how cocaine elevates
blood pressure, I think we should refocus our strategy to use
medications that will affect sympathetic stimulation of the heart
rather than medications that have effects only on blood vessels,"
SOURCE: Circulation 2002;105:1054-1059.
Reference Source 89