Myobloc (rimabotulinumtoxinB), marketed by US WorldMeds, is a medication to treat abnormal head position and neck pain that occurs in adults with cervical dystonia. The U.S. Food and Drug Administration (FDA) recently approved the supplemental biologics license application (sBLA) for Myobloc injection for the treatment of chronic drooling in adults. This includes Parkinson’s disease patients who frequently experience problematic drooling.
How Myobloc works
The active ingredient in Myobloc, botulinum toxin type B, works by blocking the transmission of nerve signals to muscles and salivary glands. It performs its function by inhibiting the neurotransmitter acetylcholine, a signaling molecule that stimulates the release of saliva. Myobloc is injected into saliva-producing glands — the parotid and submandibular glands — to reduce excessive drooling.
Myobloc in clinical trials
A double-blind, placebo-controlled randomized Phase 2 clinical trial (NCT00515437) assessed different doses of Myobloc to determine the safety, tolerability, and effectiveness for the treatment of drooling in Parkinson’s disease patients. A total of 54 participants were randomized to receive a single dose of 1,500, 2,500, or 3,500 units of Myobloc, or a placebo. Patients were followed for 20 weeks after injection. Saliva production was measured by the unstimulated salivary flow rate (USFR), and any changes in symptoms were assessed using the clinical global expression of change (CGI-C). The USFR is measured in milliliters (mL) per minute, and the CGI-C score ranges from 1 (very much improved) to 7 (very much worse). Four weeks after treatment, the CGI scores ranged from 1.6 to 2.1 and were significantly lower with all three doses compared to placebo. There also was a significant reduction in the USFR for all three dosage groups.
Another randomized, double-blind placebo-controlled Phase 3 clinical trial (NCT01994109) included 187 participants with troublesome drooling, of whom 122 had Parkinson’s disease. The participants received a single dose of 2,500 or 3,500 units of Myobloc, or a placebo. Four weeks after treatment, the decrease in USFR was significantly greater for patients treated with Myobloc compared to placebo. Also, the CGI-C score was significantly lower in the treated groups.
Following the completion of the randomized part of the trial, 114 patients received four consecutive treatments with 3,500 units of Myobloc every 11 to 15 weeks in an open-label manner. The study demonstrated that Myobloc is safe and effective over time at subsequent dosing sessions for more than one year.
Common side effects of using Myobloc use are dry mouth, dental decay, and dysphagia (swallowing problems).
Last updated: Sept. 5, 2019
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