Morbidity and severity of COVID-19 in patients with Parkinson's disease treated with amantadine - A multicenter, retrospective, observational study

BACKGROUND: After more than 2 years of the pandemic, effective treatment for COVID-19 is still under research. In recent months, publications hypothesized amantadine's potential beneficial effect on SARS-CoV-2 infection. OBJECTIVE: To compare the groups of Parkinson's Disease (PD) patients who were administered amantadine chronically and those who did not take this medication in the context of the incidence and severity of COVID-19 infection. METHODS: An observational, retrospective, multicenter cohort study was conducted among consecutive patients with idiopathic PD. The structured questionnaires were completed during the patient's follow-up visits at the Outpatient Clinic or during hospitalization. The questionnaire included the following informations: patient's age, duration of PD, Hoehn-Yahr (H–Y) stage, comorbidities, medications, COVID-19 confirmed by reverse transcription polymerase chain reaction (RT-PCR) swab test for SARS-CoV-2 with specified symptoms and their severity (home or hospital treatment). The vaccination status was verified as well. RESULTS: Five hundred fifty-two (n = 552) patients participated in the study - 329 men (60%). The mean H–Y stage was 2.44 (range: 1–4) and the mean duration of PD was 9.6 years (range: 1–34). One hundred four subjects (19%) had confirmed COVID-19 infection. Subjects over 50 years of age had a significantly lower incidence of COVID-19 (17% vs 38%, p = 0.0001) with difference also in mean H–Y stage (2.27 vs 2.49; p = 0.011) and disease duration (8.4 vs 9.9 years, p = 0.007). There were no differences between patients with and without co-morbidities. In the whole analyzed group 219 (40%) subjects were treated with amantadine. Comparing COVID-19 positive and negative patients, amantadine was used by 48/104 (46%) and 171/448 (38%) respectively. 22% of patients on amantadine vs. 17% of patients without amantadine developed COVID-19. These differences were not significant. There were no differences in morbidity and severity of COVID-19 between amantadine users and non-users as well. CONCLUSIONS: COVID-19 was less common in older (>50) with longer duration and more advanced patients. Amantadine did not affect the risk of developing COVID-19 or the severity of infection.