The Poison Review

Tricyclic antidepressant poisoning treated by magnesium sulfate: a randomized, clinical trial. Emamhadi M et al. Drug Chem Toxicol 2012 Feb 7 [Epub ahead of print]

Abstract

The authors claim that they “evaluated the effect of magnesium sulfate in the treatment of TCA [tricyclic antidepressant] intoxication” by performing a randomized clinical trial. They had 72 subjects, a control group [N = 36] who received standard care (including sodium bicarbonate), and a study group [N = 36] who received standard care plus intravenous magnesium sulfate 1g/q 6 hours. They found a statistically “marginal” improvement in the mortality rate between the control and study groups (12 v 5 deaths, respectively, p = 0.052) and a statistically significant benefit in length of ICU stay between the two groups (83 v 26 hours respectively, p < 0.001). They conclude that magnesium sulfate is effective in the treatment of TCA cardiovascular toxicity, but that more study with large sample sizes are needed.

Well, maybe not. Unfortunately, there are so many problems with this paper that it’s impossible to accept any of its findings. For one thing, there is no description of study’s randomization methods — we’re left to take it on faith that they were valid. In addition, such little clinical information is reported that we really can’t evaluate the results. What TCA’s were involved? How did the fatalities die? How long after presentation? How sick were the patients in each group? (We’re given some baseline data such as time from ingestion, pH, QRS duration, and presence or absence of seizures, but only the mean for each group, not the range.)

In my opinion, this study has absolutely no face validity. When patients who overdose on TCAs go bad, it happens usually in the first several hours. I find no reason to believe that a piddling infusion of magnesium sulfate would be responsible for a mean reduction in ICU stay of 2+ days.

Finally, the authors state that their results are “consistent with previous studies reporting on the efficacy of magnesium sulfate in the treatment with TCA intoxication”. One of the papers they reference to support this statement is by Woolf et al (Clin Toxicol 2007;45:203-233). That paper was about out-of-hospital management of TCA overdose, and has absolutely nothing in it about IV magnesium sulfate.