Quercetin–bromelain supplementation and clinical outcomes of COVID-19: a randomized, double-blind, placebo-controlled trial in hospitalized patients in Tunisia
RCT 244 hospitalized, severely hypoxemic COVID-19 patients in Tunisia reporting lower respiratory deterioration with quercetin + bromelain. The trial was registered retrospectively in June 2024, two years after completion, and shows signs of outcome switching: the sample size was calculated for a reduction in mortality, and the introduction frames mortality and complications as the aim. The definition of respiratory deterioration (SpO₂ falling below 94%) cannot apply to most participants, whose mean baseline SpO₂ was ~79%, and the definition of escalation is unspecified. Event counts are difficult to reconcile: 93 deaths and 68 patients on NIV, but only 37 respiratory-deterioration events and 4 intubations. A co-author is affiliated with the product’s manufacturer and authors declare no competing interests.
This study is excluded in meta-analysis:
multiple significant issues pending author response, see discussion.
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risk of death, 14.0% lower, RR 0.86, p = 0.43, treatment 43 of 122 (35.2%), control 50 of 122 (41.0%), NNT 17.
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risk of mechanical ventilation, no change, RR 1.00, p = 1.00, treatment 2 of 122 (1.6%), control 2 of 122 (1.6%).
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risk of progression, 58.0% lower, RR 0.42, p = 0.007, treatment 11 of 122 (9.0%), control 26 of 122 (21.3%), NNT 8.1, respiratory deterioration.
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hospitalization time, 7.7% higher, relative time 1.08, p = 0.37, treatment mean 11.22 (±8.24) n=122, control mean 10.42 (±5.76) n=122.
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Effect extraction follows pre-specified rules prioritizing more serious outcomes. Submit updates
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Gargouri et al., 13 Oct 2026, Double Blind Randomized Controlled Trial, Tunisia, peer-reviewed, 9 authors, this trial uses multiple treatments in the treatment arm (combined with quercetin) - results of individual treatments may vary.
