Single-Arm Pilot Study of Compounded DMSO-Based Dual-Route Therapy for Refractory Subjective Tinnitus in PASC and Post-COVID-19 Vaccine Injury

Inclusion Criteria

Inclusion Criteria: * Inclusion Criteria: Adults 18 to 70 years of age. Chronic subjective non-pulsatile tinnitus for at least 6 months. Bothersome tinnitus defined by a Tinnitus Handicap Inventory (THI) score ≥ 20 at screening. Documented history of post-acute sequelae of SARS-CoV-2 (PASC, long COVID) or post-COVID-19 vaccine injury, with tinnitus onset or clear worsening temporally associated with that event. Failure of at least two prior tinnitus therapies (for example, sound therapy, counseling or cognitive-behavioral approaches, pharmacologic treatments, or steroid therapy). Willing and able to provide informed consent. Able to complete telemedicine visits and electronic questionnaires in English and to attend a baseline in-person otolaryngology (ENT) evaluation. Exclusion Criteria: Objective or pulsatile tinnitus, or tinnitus primarily synchronous with the heartbeat. Active middle-ear infection, acute otitis media, tympanic membrane perforation, or current otorrhea. Recent exposure (within the past 3 months) to known ototoxic medications associated with new or rapidly worsening tinnitus. Known hypersensitivity or allergy to dimethyl sulfoxide (DMSO) or any component of the study formulations (betahistine, dexamethasone, lidocaine, levocarnitine, N-acetylcysteine, or excipients). Pregnancy or breastfeeding. Uncontrolled or severe psychiatric illness (for example, active psychosis, acute suicidality) that, in the opinion of the investigator, would interfere with participation or completion of questionnaires. Inability to comply with study procedures, including telemedicine visits, electronic data capture, or topical/otic dosing instructions. Any other otologic or neurologic condition judged by the investigator to confound tinnitus assessment or pose unacceptable risk with DMSO-based therapy.