Background Recent meta-analyses of randomized controlled trials (RCTs) claimed efficacy of higher-dose fluvoxamine (2 × 100 mg/day, as opposed to 2 × 50 mg/day) in prevention of disease deterioration in adults with mild - moderate COVID-19 disease.

Objectives Investigate whether such claims are supported by the data.

Methods Systematic review and meta-analysis of RCTs evaluating higher-dose fluvoxamine in this indication.

Results Seven studies declared as RCTs were identified, one of which was severely biased (open-label, non-standardized and unreported standard of care as a control), and eventually ended as non-randomized (huge attrition). Composite endpoints of deterioration in the 6 included placebo-controlled trials contained elements susceptible to error and bias. Three trials were small (<100 patients/arm), three were larger (270 - 750 patients/arm). Deaths and need for mechanical ventilation were sporadic and observed in only one trial. Hospitalizations were also sporadic in 5/6 trials. Frequentist methods generally appropriate for random-effects analysis of low number of trials with rare outcomes (generalized linear mixed models, beta-binomial or binomial-normal) greatly underestimated heterogeneity, but still did not document benefits regarding the composite endpoints or hospitalizations. Bayesian hierarchical models revealed huge heterogeneity and indicated no benefit regarding: (i) composites of deterioration, large trials OR = 0.78 (95% CrI 0.55 - 1.21); multiplicity corrected OR = 0.87 (0.64 - 1.21); (ii) hospitalizations, small trials OR = 0.88 (0.45 - 1.72); large trials OR = 0.94 (0.52 - 1.75); all trials OR = 0.81 (0.47 - 1.43). Heterogeneity was unlikely due to clinical particulars (vaccination status, treatment duration, time horizon), and more likely due to unidentified bias.

Conclusions RCTs do not support efficacy of higher-dose fluvoxamine in prevention of disease deterioration in adults with mild - moderate COVID-19 disease.

The authors have declared no competing interest.

This study did not receive any funding

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