Design and development of a novel supportive care product for the treatment of sialorrhea in Parkinson's disease

Abstract

Sialorrhea or excessive drooling is a significant medical issue in Parkinson’s disease (PD) and neurodegenerative disorders, although it is often underreported by patients. Sialorrhea affects a large proportion of PD patients, ranging up to 78% in advanced stages, with many PD patients considering drooling as their worst non-motor symptom. Sialorrhea affects up to a million patients with diverse neurological impairments, including cerebral palsy, amyotrophic lateral sclerosis (ALS), Huntington’s, survivors of stroke and severe traumatic brain injury. Numerous approaches have been attempted to treat sialorrhea in PD patients, including surgical procedures, prosthetic devices, botulinum injections, systemic anticholinergic drugs, and speech and behavioral therapy. A novel drug treatment (NH004) to control the symptoms of sialorrhea is under development. The active ingredient is the anticholinergic drug tropicamide. Anticholinergic drugs work by blocking acetylcholine muscarinic receptors and ultimately decreasing saliva secretion via the reduction of parasympathetic autonomic nervous system activity. The tropicamide is delivered in a thin film designed to adhere to the buccal mucosa and to slowly dissolve within the oral cavity, allowing the drug to reach the underlying salivary gland. A pilot study testing NH004 in PD patients has suggested a potentially useful sialorrhea-reducing effect with NH004 compared to placebo. The advantages of NH004 include local bioavailability with low systemic exposure, rapid onset of action and, importantly, convenience of use for patients. This review summarizes the current knowledge and impact of sialorrhea as a common non-motor symptom in PD, treatment options, the anticholinergic drug tropicamide, the design and development of the thin film drug delivery system, and NH004 for the treatment of sialorrhea.