Calling it very effective for cough is probably a bit of stretch. Some studies have shown that DXM is marginally better than placebo [1].
[1] https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD...
in my experience it can be effective for some people but mostly at much higher dosage than usually recommended.
in my experience it can be effective for some people but mostly at much higher dosage than usually recommended.