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CURITIBA, Brazil, Oct. 25 - Everyone's favorite toxin appears to offer significant relief from severe facial pain.

When Botox (botulinum-A toxin) was injected into the faces of 13 patients with severe, painful symptoms from trigeminal neuralgia, all had significant reductions in pain, according to researchers here and at Thomas Jefferson Hospital in Philadelphia.

Four of the 13 were able to stop taking pain medications altogether, and the rest were able to reduce their use of pain medications by more than half, reported Elcio Juliato Piovesan, M.D., and colleagues in the Oct. 25 issue of Neurology.

"Drugs are not always effective in treating trigeminal neuralgia," said Dr. Piovesan, a neurologist at the Clinical Hospital of the Federal University of Parana. "Some patients avoid them because of side effects, and then their pain is more intense and longer-lasting."

To determine the minimal dose for effective treatment of trigeminal neuralgia and to assess the duration of relief, the authors conducted an open-label study in 13 patients, all of whom met International Headache Society criteria for trigeminal neuralgia. Four of the patients had symptoms in just one nerve branch of the trigeminal nerve and nine had symptoms in two or more branches.

Patients reported their medication use at baseline and at 60 days post injections. Patients were evaluated at 10, 20, 30 and 60 days following Botox injection.

All patients at baseline reported severe, painful symptoms that correlated on a visual analog scale with the size of the painful area.

The dose of Botox used depended on the reported pain surface, and ranged from 6.83 to 9.11 units.

"Pain intensity was significantly reduced at the first evaluation after treatment with [Botox] and [the treatment] reached its peak effect at the 20-day evaluation," the authors wrote.

At the 60-day follow-up visit, four patients reported that they were medication free, and the remainder said they had reduced their pain-meds use by more than 50%.

Three patients who took multiple drugs without benefit before Botox injection were taking only one drug at a smaller dosage at last follow-up, the authors noted.

"Most of our patients reduced their preventive medication by more than 50%, others stopped them completely, and some taking multiple medications converted to monotherapy," the investigators wrote. "No adverse interactions between analgesic, prophylactic medication, and [Botox] injection have been reported; we did not observe any in our study. The therapeutic effects of [Botox] were not due to increased potency of preventive medication, because many of our patients discontinued their preventive medication and improved."

They acknowledged that follow-up was not long enough to determine the precise duration of effect of botulinum-A toxin injection for this indication.

Botox, best known these days for masking the effects of aging, was originally approved to correct eyelid and ocular muscle problems. In the U.S., Botox is approved for the treatment of blepharospasm, strabismus, cervical dystonia (e.g., torticollis), and severe hyperhidrosis.

Botox Cosmetic is approved for "temporary improvement in the appearance of moderate to severe glabellar lines associated with corrugator and/or procerus muscle activity in adults."

The toxin works by binding to acceptor sites on motor nerve terminals to inhibit the release of acetylcholine, and blocks the release of other neurotransmitters from presynaptic nerve endings.

Botox has been used in clinical trials with apparent good effect for treatment of pain related to migraines, temporomandibular joint syndrome, post-surgical pain syndromes, and idiopathic trigeminal neuralgia, Dr. Piovesan and colleagues wrote.

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