MYOBLOC® Injections

Muscle-relaxing MYOBLOC® injections contain neurotoxins derived from the toxin Clostridium botulinum, the same bacterium that causes food poisoning, to treat pain and a variety of conditions. MYOBLOC injections, which are similar to BOTOX® injections, can also be used for cosmetic purposes. Serious conditions in which MYOBLOC injections are used as treatment include the following:

  • Migraine or other headaches
  • Pain due to arthritis, injury or other causes
  • Muscle spasms
  • Spasticity
  • Cervical dystonia (painful stiffness of the neck)
  • Urinary incontinence or overactive bladder
  • Blepharospasm
  • Strabismus
  • Hyperhidrosis (excessive sweating)

Although large numbers of children with cerebral palsy are treated with MYOBLOC injections, such usage is considered "off label," which means that MYOBLOC injections have not yet been approved by the United States Food and Drug Administration as treatment for that particular condition.

Candidates for MYOBLOC Injections

Although MYOBLOC injections can be beneficial for patients suffering from a variety of conditions, they are not recommended for everyone. Pregnant or nursing women, and patients with certain medical conditions or who are taking particular medications, should not get the injections. Children with muscle spasms are at greatest risk of complications from MYOBLOC injections.

MYOBLOC Injection Procedure

MYOBLOC injections work by blocking the release of acetylcholine, which causes muscles to contract. As a result, muscle spasms are interrupted, eliminating pain or alleviating the condition the patient is experiencing. MYOBLOC injections start working within a few days of the patient's receiving them, with maximum relief reached after about 2 weeks. The positive effects of the injections can last for up to 6 months.

For accuracy in pinpointing the muscle fibers that need to be treated, MYOBLOC injections may be administered in conjunction with electromyography (EMG).

Risks of MYOBLOC Injections

Although MYOBLOC injections offer relief from pain for many patients, there is some risk involved in getting them. Lesser reactions, such as tenderness at the injection site and minor flu-like symptoms that usually resolve in 24 hours, are not uncommon. The more serious threat is that the medication can spread to other parts of the body after the injection, possibly resulting in serious, or even fatal, side effects. Such complications can occur hours, or even weeks, after injection.

The risk of serious complications is minimal when patients are given MYOBLOC injections for cosmetic reasons, eye spasms or excessive sweating. Patients treated for muscle spasms, or who have preexisting conditions, including breathing or swallowing difficulties, are more susceptible to complications which, though rare, may include:

  • Muscle weakness
  • Blurred or double vision
  • Irregular heartbeat
  • Chest pain
  • Difficulty breathing, talking or swallowing
  • Urinary incontinence

The positive effects of MYOBLOC injections may last for several months, but they are not permanent. Repeating them every 3 or 4 months is recommended for continual relief of symptoms. In conjunction with the injections, physical therapy is often recommended in order to restore flexibility and muscle function. In rare cases, a patient may form antibodies that prevent MYOBLOC injections from being effective. To minimize that risk, maintaining intervals between injections is required.

Additional Resources