To the Editor:
We appreciate the work of M. Bretaudeau Deguigne et al. in further exploring the role that gastric decontamination may play in lithium overdose.Citation1 Given the delay in peak serum levels following the ingestion of sustained release preparations, the existence of a digestive store of lithium has been demonstrated in pharmokinetic studies.Citation2 Theoretically, if mobilization and clearance of this digestive store could be facilitated early in overdose, peak serum levels and thus toxicity associated with overdose could be mitigated. M. Bretaudeau Deguigne et al. state that their study demonstrates a beneficial role for sodium polystyrene sulphonate and whole bowel irrigation (WBI) in improving pharmokinetics and clinical outcomes in lithium-poisoned patients, however we have some concerns about their path to these conclusions.
First, the comparison groups are strikingly dissimilar, particularly the average time to presentation for the delayed or no digestive track decontamination group is significantly longer than the early decontamination group. This delay in presentation and treatment could account for the higher peak serum lithium levels and more negative clinical outcomes such as decreased GCS and increased poison severity score seen in the delayed or no digestive tract decontamination group.
The lack of standardization and detail regarding treatment modalities in this study makes it hard to apply to clinical practice. Many patients received sodium polystyrene sulphonate and WBI, and the regimens were not consistent across treated patients. Additionally, the authors only report peak serum lithium levels, and do not clarify at what point during the treatment course that these levels were drawn. An alternative approach would be to analyze the pre- and posttreatment lithium levels in the patients receiving bowel decontamination.
Lastly, the ability of sodium polystyrene sulphonate to mobilize a digestive store of sustained release lithium is questionable. Sodium polystyrene sulphonate has been shown to decrease serum levels of lithium by binding of lithium cations in the digestive tract, but this effect is modest at best. Two volunteer studies have shown average decreases in highest serum lithium level of 0.07 mEq/L with a 30 g dose and 0.20 mEq/L with a 60 g dose.Citation3,Citation4 A retrospective cohort study of 12 patients treated with sodium polystyrene sulphonate found that the median percentage of Li removal was 15.8% (95% CI 7.2–20.1%).Citation5 At the serum levels often seen in acute on chronic overdose patients, decreases in lithium levels of this magnitude are likely to have little or no clinical effect.
M. Bretaudeau Deguigne et al. highlight the need for further investigation into the role of early gastric decontamination, particularly the use of WBI in acute potentially toxic lithium ingestions. Early decontamination could decrease the amount of lithium absorbed obviating the need for forced diuresis, admission, and hemodialysis in treating lithium toxicity.
Declaration of interest
The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.
References
- Bretaudeau DM, Hamel JF, Boels D, Harry P. Lithium poisoning: the value of early digestive tract decontamination. Clin Toxicol 2013; 51:243–248.
- Friedberg RC, Spyker DA, Herold DA. Massive overdose with sustained-release lithium carbonate preparations: pharmacokinetic model based on two case studies. Clin Chem 1991; 37:1205–1209.
- Tomaszewski C, Musso C, Pearson JR, Kulig K, Marx JA. Lithium absorption prevented by sodium polystyrene sulfonate in volunteers. Ann Emerg Med 1992; 21:1308–1311.
- Belanger DR, Tierney MG, Dickinson G. Effect of sodium polystyrene sulfonate on lithium bioavailability. Ann Emerg Med 1992; 21: 1312–1315.
- Ghannoum M, Lavergne V, Seng Yue C, Ayoub P. Successful treatment of lithium toxicity with sodium polystyrene sulfonate: a retrospective cohort study. Clin Toxicol 2010; 48:34–41.