The Food and Drug Administration (FDA) has approved Myobloc (rimabotulinumtoxinB injection; US WorldMeds) for the treatment of chronic sialorrhea in adults.

The approval was based on multiple studies, including a double-blind, placebo-controlled trial, followed by an open-label treatment period, in 187 patients with chronic, troublesome sialorrhea for at least 3 months. Patients were randomized to receive Myobloc injections (divided among the parotid and submandibular glands) or placebo. The co-primary efficacy end points included change from baseline in Unstimulated Salivary Flow Rate (USFR; change weight of expectorated saliva) and the Clinical Global Impression of Change (CGI-C) assessed 4 weeks after treatment; CGI-C was assessed on a 7-point scale ranging from “very much improved” (1) to “very much worse” (7).

Results showed that at Week 4, change from baseline in USFR was significantly greater for patients treated with Myobloc than in patients on placebo. In addition, CGI-C scores were significantly lower in patients treated with Myobloc than in patients on placebo. Data from the open-label portion of the study showed that the treatment was safe and effective following subsequent administrations over a 1-year period. 

According to the product labeling, the frequency of Myobloc repeat treatments should be determined by clinical response, but should generally be no more frequent than every 12 weeks. The typical duration of effect following a single treatment was observed to be up to 3 months, however the effect may vary in individual patients.  

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Myobloc, an acetylcholine release inhibitor, is supplied in single-dose vials containing 2500 Units/0.5mL, 5000 Units/mL, and 10,000 Units/2mL. It is also approved for reducing the severity of abnormal head position and neck pain associated with cervical dystonia in adults.

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