Myobloc article posted on Yahoo..
Botulinum toxin B may be made to last longer. (Dosing Investigation). Timothy F. Kirn.
Full Text: COPYRIGHT 2002 International Medical News Group
VAIL, COLO. -- The faster a patient responds to Myobloc, the longer it will last, Dr. Neil Sadick said at a symposium sponsored by the American Academy of Facial Plastic and Reconstructive Surgery.
In an investigation that looked at three different doses of Myobloc (botulinum toxin type B, Elan Pharmaceuticals) to treat glabellar wrinkles, Dr. Sadick, professor of dermatology at Cornell University, New York, found that patients who respond to Myobloc the soonest have the longest-lasting paralysis, though the effect is still shorter than with Botox (botulinum toxin type A, Allergan Inc.).
Increasing the amount used made both the onset of action faster and the duration of action longer, Dr. Sadick said at the symposium, also sponsored by the American Society of Dermatologic Surgery.
In Dr. Sadick's study, 30 patients were treated with Myobloc, which was diluted to a concentration where 75 U was equivalent to 1 U of Botox; patients were given six injections, two in the procerus muscle and two medial and two lateral injections in the corrugator muscles, for a total dosage of 1,800 U. Sixteen patients were treated in exactly the same way at a dilution equivalent to 100:1, with a total of 2,400 U. Twelve patients were treated with a dilution equivalent to 125:1, for a total of 3,000 U.
In the 1,800-U patients, all had complete paralysis by 72 hours. In the 2,400-U patients, mean onset was 48 hours. In the 3,000-U patients, mean onset was 42 hours, and many patients had onset within 24 hours so that 94% had some diminution of wrinkling by 48 hours.
The rapidity of onset correlated with duration of action so that in the low-dose group, patients who had onset within 24 hours had a mean duration of effect of 9.5 weeks, while those whose onset took 72 hours had a mean duration of only 6 weeks. In the medium-dose patients, those with onset within 24 hours had a mean duration of effect of 10 weeks, compared with a mean of 9 weeks for those whose onset took 72 hours.
Overall mean duration of action was 8.35 weeks for the low-dose group, 9.6 weeks for the medium-dose group, and 11.2 weeks for the high-dose group. In the high-dose group, duration ranged from 8 to 13 weeks. The duration of action generally reported for Botox is 16 weeks in the glabellar region.
Although Myobloc appeared to diffuse throughout the area treated more readily than Botox, adverse effects were minimal in all the groups and comparable with Botox, Dr. Sadick said. There was none of the dry mouth that was a possible concern with Myobloc based on early studies.
Even in the high-dose group, the only side effects noted were headache in one patient, "some drooping" in another, and complaints from two patients of discomfort from the injections.
Elan Pharmaceuticals is following studies such as his to perhaps alter the formulation of Myobloc for best effect, Dr. Sadick said. "I still don't believe we have the optimal dosing."
The more pronounced diffusion of Myobloc noted consistently throughout the dose groups was striking, Dr. Sadick said. In some of the patients, the effect spread well up into the frontalis muscle. Because of this, in a continuation of this study in which patients will be treated with 3,600 U, the patients will be treated with three injections instead of six, he said.
Some physicians have predicted that Myobloc is going to be more expensive than Botox because it does not last as long. Others say they welcome the Myobloc alternative because they believe Elan will have to price their product competitively, and the end result is likely to be a lower price for both products.
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