| Study | Reason for exclusion |
|---|---|
| Ahrens 2000 | Trial registration only, no results or report available |
| DeCastro 2009 | Retrospective cohort study, no randomized controlled trial |
| Romagnoli 1999 | Two separate placebo controlled studies |
| Shipalana 1994 | Placebo controlled study |
| Singh 2022 | Ineligible study design, web‐based survey |
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