Stuart Isaacson, MDStuart Isaacson, MD
The effects of treatment with rimabotulinumtoxinB (Myobloc; US WorldMeds) for sialorrhea are both rapid and long-lasting, according to 2 new analyses presented at the 2019 International Congress of Parkinson Disease and Movement Disorders, September 22-26, 2019 in Nice, France.

The injection was recently approved by the FDA for the treatment of chronic sialorrhea in adults, adding to its previous indication for cervical dystonia. Sialorrhea is common in a number of neurological disorders, including amyotrophic lateral sclerosis, Parkinson disease, stroke, and cerebral palsy, among others. 

At the time of approval, Stuart Isaacson, MD, director, Parkinson's Disease and Movement Disorder Center of Boca Raton, said that "sialorrhea can be highly distressing for patients and their caregivers and can have a significant, negative impact on quality of life. If left untreated, pooling of saliva can lead to irritation of the skin around the mouth, oral hygiene complications, speech difficulties, and sleep interruption. In some cases, pooling of saliva can lead to choking and aspiration pneumonia.”

At MDS 2019, investigators led by Rajesh Pahwa, MD, of the University of Kansas Medical Center, reported on the long-term safety and efficacy of rimabotulinumtoxinB in adults with troublesome sialorrhea over a 1-year period.1 Participants (N=187) enrolled in the phase 3, multicenter, open-label trial (NCT02610868) received 3500 U of the drug on day 1, with subsequent injections given once they returned to clinical baseline status (treatment interval, 11-15 weeks). If there were tolerability concerns, patients were permitted to drop down to a dose of 2500 U.

During the first treatment cycle, patients experienced a significant reduction in mean unstimulated salivary flow rate from baseline to week 4 (-0.34±0.37, P <.0001), with efficacy maintained through week 13 (P <.0001). Significant improvements from baseline to week 4 were noted on the Clinical Global Impression of Change through all treatment cycles, with efficacy similar through cycled 2-4.

Notably, 5 participants withdrew from treatment early due to an adverse event (AE), though less than 10% required a dose reduction due to tolerability. The most common AEs, most of which were mild, were dry mouth and dental caries.

In another analysis, investigators reported results of a double-blind, placebo-controlled study evaluating onset of rimabotulinumtoxinB in patients who received either 2500 U, 3500 U, or placebo over 13 weeks.2

At week 1, reductions in unstimulated salivary flow rate were noted, with a significantly greater proportion of participants in the 2500 U group with “improved” or “very much improved” ratings on the clinician- and patient-rated Global Impressions of Change at week 2 compared with placebo. Similar patient-reported improvements were noted as early as week 1 in the 3500 U group versus placebo. In addition, ratings on the Drooling Impact Score and Drooling Frequency and Severity Scale aligned with the other primary outcomes measures.  

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REFERENCES
1. Dashtipour K, Isaacson S, Lew M, Chary D, Clinch T, Pahwa R. Long-term safety and efficacy of rimabotulinumtoxinB in the treatment of adult sialorrhea. Presented at: MDS 2019. September 22-26, 2019; Nice, France. Abstract 84. mdsabstracts.org/abstract/long-term-safety-and-efficacy-of-rimabotulinumtoxinb-in-the-treatment-of-adult-sialorrhea/.
2. Bahroo L, Isaacson S, Pahwa R, Chary D, Clinch T, Lew M. Onset of action for rimabotulinumtoxinB in the treatment of adult sialorrhea. Presented at: MDS 2019. September 22-26, 2019; Nice, France. Abstract 63. mdsabstracts.org/abstract/onset-of-action-for-rimabotulinumtoxinb-in-the-treatment-of-adult-sialorrhea/.