Botulinum toxin: New developments, injection techniques

Boston - The past year has been full of new developments for botulinum toxin (BT), says Neil Sadick, M.D., F.A.C.P., F.A.A.C.S.

Botulinum toxin has become a new treatment option for hyperhidrosis. Elan Pharmaceuticals says that it is working on a reformulation of Myobloc, its Type B toxin. Also, Ipsen, Ltd. of Great Britain has moved into phase 3 trials with a new form of Type A called "Dysport."

"It can stay refrigerated for six weeks without losing much of its potency," says Dr. Sadick, clinical professor ofdermatology at the Weill Medical College at Cornell.

A versus B Dr. Sadick describes Type A as the "gold standard" for treatment of hyperkinetic facial wrinkles. Full resistance is rare. Results last from 12 to 16 weeks.

Studies of Myobloc indicate that it has a very rapid onset, reaching efficacy in less than three days. The mean duration of action for doses of 2,400 units is 9.6 weeks, and preliminary results from a study, evaluating doses of 3,000 units, suggest a mean duration of 11.2 weeks.

"More Myobloc studies are needed to evaluate the optimal dose in terms of efficacy, duration and side effects," Dr. Sadick says.

Potentially, Myobloc could be used in patients who are resistant to Type A botulinum toxin or for those who want rapid onset or seek a more diffuse, uniform freeze of the frontalis area. Because Myobloc doesn't have to be reconstituted, it can also be useful to have on hand for touch-up procedures.

Botox comes as a vacuum-dried preparation in vials of 100 units, requiring reconstitution. Myobloc, on the other hand, is premixed in three (overfilled) vial sizes. A 2,500-unit vial actually contains 4,100 units, the 5,000-unit vial has 6,800 units, while the 10,000-unit vial has 12,650 units.

Because Myobloc is less concen-trated and tends to diffuse more, he makes fewer injections. When used in combination with Type A, the effect isadditive, not synergistic.

Types A and B have similar side effects. Technique-related complications include ptosis of the brow or lid, diplopia, bruising, a decrease in tearing, infection and contour irregularities. Other adverse events include idiosyncratic reactions, such as transient numbness and headaches; muscle spasms; myasthenia; and immunologic reactions.

To avoid complications, Dr. Sadick suggests:

Disclosure: Dr. Sadick consults with many pharmaceutical and laser companies, including Allergan.