Rationale for using Fluvoxamine (=SSRI) in the treatment of Covid-19 patients:

Fluvoxamine binds to the sigma-1 receptor and stimulates this receptor which is found in immune cells (NIH, 2021). This leads to decreased synthesis of pro-inflammatory cytokines (interferon gamma, tumor necrosis factor alpha, interleukin-1, -2, -6, -12 ). Covid-19 is referred to as the cytokine storm with widely distributed inflammation all over the body.  Fluvoxamine can thus be useful as it is anti-inflammatory through reducing cytokine synthesis. 

Reference list:

1.  NIH (National Institutes of Health). 2021. Fluvoxamine COVID-19 treatment guidelines. https://www.covid19treatmentguidelines.nih.gov/therapies/immunomodulators/fluvoxamine/ Date of access: 27 Oct. 2021