Byambasuren 2026: low-dose naltrexone for long covid, a review

What they tested

The reviewers searched PubMed, Embase, the Cochrane Library and trial registries through 5 May 2026 for randomized trials and pre-post studies in people with long covid. Pre-post studies measure symptoms before and after treatment, with no comparison group.

They pooled results with random-effects models and assessed risk of bias with the Newcastle-Ottawa Scale.

What they found

Of 397 titles and abstracts screened, no randomized controlled trials were found. Four observational pre-post studies from the USA and Ireland, with 155 people, met the criteria. Doses ranged from 1 mg to 6 mg a day.

Pooled before-and-after results showed moderate effects for less fatigue (Hedges' g = -0.74), less brain fog (g = -0.53) and better sleep quality (g = -0.60), and large effects for pain and daily functioning (both g = -0.93), in favour of low-dose naltrexone.

Heterogeneity, how much results differed between studies, ranged from 0% to 62%. Only two studies assessed safety, and neither reported serious adverse events.

Limits

• None of the included studies had a comparison group, so improvements could reflect natural recovery or the placebo effect rather than the drug.
• The studies were small, and the authors rated the certainty of the evidence as low.
• Only two studies looked at safety.

What it means if you're considering naltrexone

Low-dose naltrexone for long covid is unproven. People in these small studies reported feeling better, but without a placebo group that can't be credited to the drug. The authors say well-powered trials are needed to confirm whether it works, at what dose and for whom.