Johns Hopkins Gazette: July 25, 1994

By Mike Field

Anyone who has ever bitten into a hot chili pepper will know
the feeling: a searing pain on the lips and tongue that no
amount of water or ice can seem to cool. Now Hopkins researcher
Marco Pappagallo is ready to begin clinical trials that will
use the burning properties of hot peppers to combat an
affliction common to AIDS patients and some diabetics.
     The fuel that fires the pepper's burning heat is
capsaicin, a naturally occurring compound found in pungent
peppers such as the jalapeno, used commonly in Mexican cuisine.
Capsaicin, it is hoped, will provide relief to thousands who
suffer from a potentially crippling condition brought on by
their disease.
      Known as painful peripheral neuropathy, the degenerative
condition is marked by searing pain on the bottom of the feet
that can often immobilize its victims. "In these patients the
disease causes the nociceptors, or pain fibers, to die back,"
said Dr. Pappagallo, a faculty member in the School of
Medicine. "This causes an intense burning sensation at the end
of the feet that can make walking unbearably painful." 
     An ointment containing a high concentration of capsaicin
can block painful peripheral neuropathy by temporarily "burning
out" the nerve receptors in the feet, Dr. Pappagallo's studies
     "The capsaicin knocks out pain receptors in rats and mice;
we're assuming it will do the same for humans," he said.
Research suggests that a single application of the capsaicin
cream -- extracted from a chili pepper paste -- could stop pain
for several weeks and possibly several months.
     "Capsaicin activates pain fibers and then appears to
desensitize them," Dr. Pappagallo said. "We know from hot
peppers that eating spicy food desensitizes the palate,
allowing the person to eat hotter and hotter food. If you stop,
however, there is an eventual full recovery of sensitivity."
     Dr. Pappagallo received FDA approval to conduct clinical
trials of a 5 percent capsaicin cream on AIDS patients
suffering from painful peripheral neuropathy. So potent is the
concentrated cream that the procedure will have to be performed
at the hospital, and the participants in the study will receive
a local anesthetic before the cream is applied.
     "We will use an epidural block to numb the feet and legs,"
he said. "Since this is a pilot project we'll start with a 5
percent concentration, but we may have to go to 10 percent or
more. By the time the anesthetic wears off the burning
sensation caused by the capsaicin will be gone and, hopefully,
the pain fibers will be numb."
     Once the nerves are desensitized, patients would maintain
the numbness by regular applications of an over-the-counter
sore muscle cream currently available that contains small
amounts of capsaicin as its active ingredient.
     "If effective, the use of this naturally occurring
compound would provide pain relief that is cheap, easy to
administer and shows no evidence of toxicity," Dr. Pappagallo
said. "About 10 percent of AIDS patients suffer from painful
peripheral neuropathy, and currently there is no truly
effective treatment available. This could provide relief to
many, many people."
     Dr. Pappagallo is actively recruiting AIDS patients with
this condition for the trials. Interested parties should call
955-7338 for further information.

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