Botulinum Toxin Therapy
Botulinum toxin therapy: To B or not to B
Recently, a 52-year-old female patient with cervical dystonia [CD] was referred to my movement disorder clinic for botulinum toxin injections. She had tried oral medications, physical therapy and chiropractic care without significant relief. The severe pain bothered her the most, but her head pulling concerned her, too. After some discussion, I decided to treat her with botulinum toxin type B [Myobloc] injections.
Within one week the patient reported significant relief in her symptoms. She noted 90 percent improvement in her pain and 60 percent improvement in her neck movement. We continue to treat her with Myobloc today and achieve strong results.
For many years I have been injecting both [botulinum drugs]drugs for disorders ranging from CD to bladder spasticity. Many physicians use Myobloc only as an alternative for patients who become resistant to botulinum toxin type A [Botox]. I use both toxins as first line treatments for my CD patients. Patients ask me how I decide which botulinum toxin is right for them. Ultimately you and your doctor need to make the decision together, but there are different situations for which I will use Myobloc and Botox.
Although both drugs are FDA approved as safe and effective in the treatment of CD, they differ in the way they work. While both relax muscles and decrease pain, they do so by blocking different proteins responsible for the release of acetylcholine [a substance that causes muscle to contract]. Based on my experience, I prefer to use Myobloc for conditions with significant pain such as headache, CD and myofascial pain. On the other hand, I prefer to use Botox for patients with conditions that are characterized by pulling or spasticity rather than pain.
Primate studies suggest that Myobloc does not spread to other muscles as much as Botox. Based on this information, I like to use Myobloc where I don’t want much “spread,” like in the smaller muscles of the hand. I suggest all physicians become familiar with the use of both toxins in their practices so they can better serve their patients needs.
For instance, by becoming familiar with both toxins, I have found administering 100 to 400 units of Botox for CD and 5,000 to 17,500 units of Myobloc for CD to be the most effective doses. It is important to note that there is not a dose conversion between Myobloc and Botox. Physicians generally follow published dosing guidelines for each muscle group. To limit any potential side effects, both products should be administered conservatively and then the dose can be slowly increased depending on the patient’s response. They are also packaged differently and have different shelf lives. Myobloc comes in three dose sizes and can be stored in the refrigerator for up to 21 months and is expecting the FDA to soon approve a label change for storage beyond 21 months; Botox comes in one dose size and is stored in the refrigerator for up to 24 months. Myobloc is “ready to use” and Botox must be prepared or “reconstituted” [usually with preservative free normal saline].
Typical side effects for both drugs may include mild difficulties with swallowing, flu-like symptoms and injection site pain. Some patients report that Myobloc may also cause dry mouth and an acid stomach or cause a mild burning sensation that quickly subsides when Myobloc is injected. This may be because Myobloc is slightly acidic when injected. However, there are simple ways for physicians to alleviate this burning sensation by using diluting agents such as sodium bicarbonate, normal saline with preservative or a local anesthetic.
Some information suggests that Myobloc may work more quickly [within a few days] than Botox. Patients can expect the duration of both drugs to last 12-16 weeks in most muscle groups. I have not observed patients becoming resistant to one toxin more than the other. Although, if you fail to respond to one toxin, chances are very good that you will respond to the other toxin.
If you have decided to try botulinum toxin therapy and need to decide which toxin is best suited to treat your CD or other medical condition, make sure you take the time to discuss your primary treatment objectives with your physician. It is important to make sure your physician understands dosing and possible side effects for Myobloc and Botox to optimize your results. If your physician is unfamiliar with dosing, We Move has published initial dosing guidelines for both toxins.
Dennis Dykstra, MD, PhD
Associate Professor & Chairman
Department of Physical Medicine and Rehabilitation
University of Minnesota
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