Wednesday 11 May 2016

A single dose of oral dexamethasone is probably just as good as 5 days of oral prednisolone for acute asthma

Oh... this would make life simpler, so I hope it works.

Dexamethasone has a duration of action up to 72 hours. Therefore several researchers have considered it as a potential agent to streamline the treatment of asthma.

This was a triple blind “non-inferiority” trial looked at single dose of dexamethasone 12mg vs. the usual five days of prednisone (prednisolone can be considered the same). Included patients were adults with mild to moderate asthma discharged home from the ED.

The primary outcome measure was relapse as defined by an unscheduled return to a health care provider within 14 days.  (Ok... this outcome measure is not perfect but probably represented a pragmatic compromise in the design of the study.)

It was powered to an 8% difference between groups.

Why 8%?

Yes, it’s fairly arbitrary. And they provided some nebulous justification. 


They kind-of, sort-of, almost met inferiority. There was a 2.3% (95% CI -4.1% to 8.6%) absolute difference in the primary outcome of relapse at 14 days, but the confidence interval just barely crossed their pre-specified arbitrary margin of non-inferiority.

So this officially is a negative study. But I don’t really think so. Nor do the study investigators.

I’ll bet the authors are kicking themselves for not ensuring the proper statistical power in order to narrow down their confidence interval. Statistically speaking, the probability of the truth is always closer to the point estimate.  

I also bet the authors are disappointed they didn’t pick a non-inferiority margin higher than 8%!

Either way, I think this is more evidence to suggest that a single dose of dexamethasone is probably just as good as the usual course of prednisone. As we get more evidence, we will surely get a better idea of the true efficacy.

For now, stock up on the dex!


Rehrer MW, Liu B, Rodriguez M, et al. A Randomized Controlled Noninferiority Trial of Single Dose of Oral Dexamethasone Versus 5 Days of Oral Prednisone in Acute Adult Asthma. Ann Emerg Med. 2016;67:593-601.

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