Efficacy of donepezil in patients with chronic tinnitus

• Grant number: 20/14585-4
• Support Opportunities: Regular Research Grants
• Start date: April 01, 2021
• End date: June 30, 2023
• Field of knowledge: Health Sciences - Medicine
• Principal Investigator: Jeanne da Rosa Oiticica Ramalho
• Grantee: Jeanne da Rosa Oiticica Ramalho
• Host Institution: Hospital das Clínicas da Faculdade de Medicina da USP (HCFMUSP). Secretaria da Saúde (São Paulo - Estado). São Paulo , SP, Brazil
• Associated researchers: Elaine Miwa Watanabe

Abstract

Tinnitus is any perception of sound that occurs in the absence of an external acoustic stimulus. It affects 15% of the world population (Cederroth RC et al. 2019) and 22% of the population of São Paulo city (Oiticica & Bittar 2015). One of the pathophysiological mechanisms is related to the increased glutamate activity, the main excitatory neurotransmitter within the cochlea, it is excitotoxic and capable of generating tinnitus (Pujol & Puel 1999, Onishi et al. 2017). It is known that in high extracellular concentrations, glutamate acts as a potent neurotoxin, capable of inducing serious damage to target neurons. Similar to what occurs in several acute neurodegenerative diseases: epilepsy, hypoxia, anoxia, head trauma; and chronic: Alzheimer's, Amyotrophic Lateral Sclerosis, Parkinson's, Huntington's Disease, neurological processes related to HIV infection and hepatic encephalopathy (Valli & Andrade Sobrinho 2014). Donepezil has not been studied in patients with tinnitus. It is an acetylcholinesterase inhibitor medication, increasing the availability of acetylcholine. This is widely distributed in the central nervous system and plays an important role in cortical development and activity, learning and memory (Li SM et al. 2015). Donepezil also has a neuroprotective effect against glutamate-induced excitotoxicity and is commonly used in degenerative diseases such as Alzheimer's, a disease in which acetylcholine is also decreased (Almeida OP 1998). Our hypothesis is that donepezil is effective in improving the discomfort of tinnitus. Each patient will do two treatment steps: in one step, the patient will take the donepezil medication for 90 days (5mg from the 1st to the 30th day, and 10 mg from the 31st to the 90th day). Then, will be take a wash-out for 30 days, and after that will start the next step: take a placebo for 90 days. Neither the patient nor the doctor will know which step will be the first. It is a prospective, double-blind, cross-over type versus placebo study. The study variables will include: (1) THI questionnaire (Tinnitus Handicap Inventory) validated for portuguese language, (2) tinnitus discomfort measured by EVA (Visual Analog Scale), (3) IPRF (speech recognition percentage index), (4) MEEM questionnaire - Mini Mental State Exam validated for portuguese language, (5) CDR (Clinical Dementia Rating) scale validated for portuguese, (6) Psychoacoustic measures of tinnitus (pitch, loudness and minimum masking level). (AU)