Dosage & Administration
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Myobloc Prescribing Information
Postmarketing reports indicate that the effects of MYOBLOC and all botulinum toxin products may spread from the area of injection to produce symptoms consistent with botulinum toxin effects. These may include asthenia, generalized muscle weakness, diplopia, blurred vision, ptosis, dysphagia, dysphonia, dysarthria, urinary incontinence, and breathing difficulties. These symptoms have been reported hours to weeks after injection. Swallowing and breathing difficulties can be life threatening and there have been reports of death. The risk of symptoms is probably greatest in children treated for spasticity but symptoms can also occur in adults treated for spasticity and other conditions, particularly in those patients who have underlying conditions that would predispose them to these symptoms. In unapproved uses, including spasticity in children and adults, and in approved indications, cases of spread of effect have occurred at doses comparable to those used to treat cervical dystonia and at lower doses [see Warnings and Precautions (5.1)].
Cervical Dystonia
MYOBLOC is indicated for the treatment of cervical dystonia to reduce the severity of abnormal head position and neck pain associated with cervical dystonia in adults.
Chronic Sialorrhea
MYOBLOC is indicated for the treatment of chronic sialorrhea in adults.
Instructions for Safe Use
The potency units of MYOBLOC are specific to the preparation and assay method utilized. They are not interchangeable with other preparations of botulinum toxin products and cannot be compared to or converted into units of any other botulinum toxin products [see Warnings and Precautions (5.2), Description (11)] .
Each single-dose vial should only be used during one session and only for one patient. Discard any remaining solution in the vial.
MYOBLOC is ready to use; no reconstitution required.
MYOBLOC may be diluted with 0.9% Sodium Chloride Injection. Once diluted, the product must be used within 4 hours as the formulation does not contain a preservative.
Dosing for Cervical Dystonia
The recommended initial dosage of MYOBLOC for cervical dystonia patients with a prior history of tolerating botulinum toxin injections is 2,500 Units to 5,000 Units divided among affected muscles [see Clinical Studies (14.1)] . Patients without a prior history of tolerating botulinum toxin injections should receive a lower initial dosage [see Adverse Reactions (6.1)] . Subsequent dosing should be determined by the patient's individual response. MYOBLOC should be administered by physicians familiar with and experienced in the assessment and management of patients with cervical dystonia.
The duration of effect in patients responding to MYOBLOC treatment for cervical dystonia has been observed in studies to be between 12 and 16 weeks at doses of 5,000 Units or 10,000 Units [see Clinical Studies (14.1)] .
Dosing for Chronic Sialorrhea
Dosing Information
The recommended dosage of MYOBLOC for chronic sialorrhea is 1,500 Units to 3,500 Units, divided among the parotid and submandibular glands (Table 1). Patient response to treatment should be considered when determining subsequent MYOBLOC dosage [see Clinical Studies (14.2)] . The typical duration of effect of each treatment is up to 3 months; however, the effect may vary in individual patients. The frequency of MYOBLOC repeat treatments should be determined by clinical response but should generally be no more frequent than every 12 weeks.
| Gland | Recommended Dosage |
|---|---|
| Parotid | 500 Units to 1,500 Units per gland |
| Submandibular | 250 Units per gland |
Administration Information
A suitable sterile needle (e.g., 30-gauge, 0.5 inch) should be used for intra-salivary gland administration.
Figure 1: Glands for Injection in Chronic Sialorrhea
Guidelines for locating salivary glands using anatomical landmarks (Figure 1):
- 1. To inject the parotid gland, bisect the distance between the tip of the tragus (Site A) and the angle of the mandible (Site B). Inject one finger breadth anterior to this site (Injection Site 1).
- 2. To inject the submandibular gland, bisect the distance between the angle of the mandible (Site B) and the tip of the chin (Site C). Inject one finger breadth medial to the inferior surface of the point of bisection (Injection Site 2).
In clinical studies, MYOBLOC was injected using anatomical landmarks to localize the salivary glands, or using ultrasound guidance for gland location. Both methods produced similar reduction in the unstimulated salivary flow rate.
MYOBLOC is a clear and colorless to light-yellow solution available as:
- Injection: 2,500 Units/0.5 mL in a single-dose vial
- Injection: 5,000 Units/mL in a single-dose vial
- Injection: 10,000 Units/2 mL (5,000 Units/mL) in a single-dose vial
Pregnancy
Risk Summary
There are no adequate data on the developmental risks associated with the use of MYOBLOC in pregnant women. No developmental toxicity was observed in pregnant rats administered MYOBLOC by intramuscular injection during gestation and lactation, at doses producing maternal toxicity.
In the U.S. general population, the background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2% to 4% and 15% to 20%, respectively. The background risk of major birth defects and miscarriage for the indicated population is unknown.
Data
Animal Data
When MYOBLOC was administered by intramuscular injection to pregnant rats (0, 300, 1000, or 3000 Units/kg/day) or rabbits (0, 0.03, 0.1, 0.3, or 1.0 Units/kg/day) throughout gestation, no adverse effects on embryofetal development were observed. The highest dose tested in rat, which was associated with maternal toxicity, was 36 times the maximum recommended human dose (MRHD) for cervical dystonia (5000 Units) on a body weight (Units/kg) basis. The highest dose tested in rabbit was substantially less than the MRHD for cervical dystonia on a Units/kg basis; maternal toxicity was observed at all but the lowest dose tested.
Lactation
Risk Summary
There are no data on the presence of MYOBLOC in human milk, the effects on the breastfed infant, or the effects on milk production. The developmental and health benefits of breastfeeding should be considered along with the mother's clinical need for MYOBLOC and any potential adverse effects on the breastfed infant from MYOBLOC or from the underlying maternal condition.
Pediatric Use
Safety and effectiveness in pediatric patients have not been established.
Geriatric Use
Cervical Dystonia
In the controlled studies for MYOBLOC in patients with cervical dystonia, 152 (75%) were under the age of 65, and 52 (26%) were 65 years of age or older [see Clinical Studies (14.1)] . For these age groups, the most frequently reported adverse reactions occurred at similar rates in both age groups. Efficacy results did not suggest any large differences between these age groups.
Very few patients age 75 or older were enrolled; therefore, no conclusions regarding the safety and efficacy of MYOBLOC within this age group can be determined.
Chronic Sialorrhea
Of the 166 MYOBLOC-treated patients in the placebo-controlled studies for treatment of chronic sialorrhea [see Clinical Studies (14.2)] , 105 (63%) were 65 years of age or older, and 43 (26%) were 75 years of age or older. No overall differences in safety or effectiveness were observed between patients over 65 years of age and younger patients, but greater sensitivity of some older patients cannot be ruled out.
MYOBLOC is contraindicated in patients with:
- A known hypersensitivity to any botulinum toxin product or to any of the components in the formulation [see Warnings and Precautions (5.3), Description (11)]
- Infection at the proposed injection site(s)