To the Editor: I am writing in regard to the review article about botulinum toxin (BTX) therapy by Eric S. Felber, DO,¹ that appeared in the October 2006 issue of JAOA—The Journal of the American Osteopathic Association. I am a neurologist in Columbus, Ohio, and I specialize in the use of BTX to treat patients with neurologic disease. I would like to clarify and correct some comments made in Dr Felber's article.¹ 

In a discussion about the preparation of botulinum toxin type A (BTX-A, or Botox), Dr Felber¹ states that vials of the toxin must be stored in the freezer until ready for use, and that once in solution, the toxin can be used for as long as 2 weeks if stored in a refrigerator. In fact, the manufacturer of Botox (Allergan Inc, Irvine, Calif) recommends that vials of unused toxin kept in the refrigerator be used within 4 hours.^2-4 However, it is true that industry data suggests the toxin may remain viable for as long as 4 weeks.⁴ This is, of course, off-label information. 

I also believe it is important to clarify both the on- and off-label uses of this medication, which were not presented clearly in the article. The US Food and Drug Administration (FDA) approved BTX-A in 1989 for the treatment of patients with blepharospasm, strabismus, and torticollis.^2,3 In 2002, the toxin was approved by the FDA for the cosmetic treatment of patients with glabellar lines only.^2,3 In 2004, BTX-A was approved for use in patients with axillary hyperhidrosis.⁵ It is important to understand that, in the United States, any other uses of BTX-A besides these conditions are considered off-label uses, even if such uses are considered the standard of care for certain conditions, including spasticity.^6,7 

In regard to the physiologic mechanism of BTX-A in cases of migraine, Dr Felber¹ states, “Another mechanism by which BTX-A may relieve migraines is in its action on pericranial muscle spasms that pull on the skull bones and their respective sutures, causing a change in intracranial pressure and pressure on the cerebral vasculature.” I do not believe that there is any literature suggesting this particular mechanism. Rather, Dr Felber's explanation would be only theoretical in nature, at best. 

Lastly, I am concerned about the five pictures in Figure 1 that depict the sites of injection—particularly the third in this sequence.¹ I believe that the use of botulinum toxin is complicated and, if not performed properly by skilled hands, it could lead to serious adverse effects. The most common adverse effects are ptosis and other problems with muscle weakness.^3,4 The pictures in the article for frontal lines and cosmetic injections show an injection site that is clearly over the superior portion of the levator palpebrae muscle (Figure 1 [C]).¹ This injection site is too low and too close to this muscle in my opinion, presenting a significant risk for ptosis in the patient. I would strongly suggest not injecting BTX-A in this region.