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Correspondence

Optimal timing for lithium levels

[version 1; peer review: 1 approved, 1 approved with reservations]
PUBLISHED 12 Jul 2022
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Abstract

Reddy and Reddy (2014) discuss the optimal timing for lithium levels in patients taking once-daily extended-release lithium formulations. They argue for blood sampling 24 h after the previous dose rather than the standard 12 h. I interpret the data quite differently. The authors start with the assumption that the clinician wants a trough level. I disagree. What one wants is to be able to compare a patient’s lithium level to the large body of published knowledge about lithium dosing. Almost all of that data comes from standard 12-h blood draws with plain (immediate-release) lithium carbonate or lithium citrate. So, the real question of interest is, with extended-release lithium formulations, at what time point does one draw the lithium level to compare most accurately with a standard 12-h blood draw with plain lithium carbonate?

The answer is not obvious because extended-release formulations affect only the absorption and not the excretion of lithium. Their primary benefit is reducing the transient peak lithium serum concentration, not delaying the (already relatively slow) elimination of lithium.

Emami and colleagues (2004) provide the needed data. First they show that 90% of the administered dose of a commercial extended-release formulation (Eskalith CR®) is absorbed by 4 h after a dose, and ~100% is absorbed by 8 h (their Figure 2A). Second, they show that at 12 h after a dose, the blood levels for immediate and extended release formulations are essentially identical (their Figure 3).  Thus 12 h after the previous dose is the ideal time for drawing blood levels for extended-release lithium tablets.

Keywords

lithium, pharmacology, administration & dosage, pharmacokinetics, blood level, concentration

Reddy and Reddy (2014) discuss the optimal timing for lithium levels in patients taking once-daily extended-release lithium formulations. They argue for blood sampling 24 h after the previous dose rather than the standard 12 h. I interpret the data quite differently. The authors start with the assumption that the clinician wants a trough level. I disagree. What one wants is to be able to compare a patient’s lithium level to the large body of published knowledge about lithium dosing. Almost all of that data comes from standard 12-h blood draws with plain (immediate-release) lithium carbonate or lithium citrate. So, the real question of interest is, with extended-release lithium formulations, at what time point does one draw the lithium level to compare most accurately with a standard 12-h blood draw with plain lithium carbonate?

The answer is not obvious because extended-release formulations affect only the absorption and not the excretion of lithium. Their primary benefit is reducing the transient peak lithium serum concentration, not delaying the (already relatively slow) elimination of lithium.

Emami et al. (2004) provide the needed data. First they show that 90% of the administered dose of a commercial extended-release formulation (Eskalith CR®) is absorbed by 4 h after a dose, and ~100% is absorbed by 8 h (their Figure 2A). Second, they show that at 12 h after a dose, the blood levels for immediate and extended release formulations are essentially identical (their Figure 3). Thus 12 h after the previous dose is the ideal time for drawing blood levels for extended-release lithium tablets.

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Version 2
VERSION 2 PUBLISHED 12 Jul 2022
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Black KJ. Optimal timing for lithium levels [version 1; peer review: 1 approved, 1 approved with reservations]. F1000Research 2022, 11:779 (https://doi.org/10.12688/f1000research.122507.1)
NOTE: If applicable, it is important to ensure the information in square brackets after the title is included in all citations of this article.
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Open Peer Review

Current Reviewer Status: ?
Key to Reviewer Statuses VIEW
ApprovedThe paper is scientifically sound in its current form and only minor, if any, improvements are suggested
Approved with reservations A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit.
Not approvedFundamental flaws in the paper seriously undermine the findings and conclusions
Version 1
VERSION 1
PUBLISHED 12 Jul 2022
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Reviewer Report 28 Jun 2024
Dean MacKinnon, Johns Hopkins University School of Medicine, Baltimore, MD, USA 
Approved
VIEWS 17
This is a brief correspondence to address somewhat dated reports that suggest altering practice with regard to the timing of therapeutic lithium levels. The author addresses a pharmacologic conjecture that a 24 hour level rather than the standard 12 hour ... Continue reading
CITE
CITE
HOW TO CITE THIS REPORT
MacKinnon D. Reviewer Report For: Optimal timing for lithium levels [version 1; peer review: 1 approved, 1 approved with reservations]. F1000Research 2022, 11:779 (https://doi.org/10.5256/f1000research.134501.r286092)
NOTE: it is important to ensure the information in square brackets after the title is included in all citations of this article.
  • Author Response (F1000Research Advisory Board Member) 28 Jun 2024
    Kevin J Black, Departments of Psychiatry, Neurology, Radiology, and Neuroscience, Washington University in St. Louis School of Medicine, St. Louis, 63110, USA
    28 Jun 2024
    Author Response F1000Research Advisory Board Member
    Thank you for your thoughtful review and clear feedback.
    Competing Interests: No competing interests were disclosed.
COMMENTS ON THIS REPORT
  • Author Response (F1000Research Advisory Board Member) 28 Jun 2024
    Kevin J Black, Departments of Psychiatry, Neurology, Radiology, and Neuroscience, Washington University in St. Louis School of Medicine, St. Louis, 63110, USA
    28 Jun 2024
    Author Response F1000Research Advisory Board Member
    Thank you for your thoughtful review and clear feedback.
    Competing Interests: No competing interests were disclosed.
Views
43
Cite
Reviewer Report 23 Nov 2022
Mehak Pahwa, Department of Psychiatry and Behavioral Sciences, University of Louisville, Louisville, KY, USA 
Approved with Reservations
VIEWS 43
I agree with the argument of measuring the level at 12 hrs after the last dose of both immediate release and extended-release. However, I don't understand why the correspondence is on a paper published in 2014 and there is only ... Continue reading
CITE
CITE
HOW TO CITE THIS REPORT
Pahwa M. Reviewer Report For: Optimal timing for lithium levels [version 1; peer review: 1 approved, 1 approved with reservations]. F1000Research 2022, 11:779 (https://doi.org/10.5256/f1000research.134501.r154972)
NOTE: it is important to ensure the information in square brackets after the title is included in all citations of this article.
  • Author Response (F1000Research Advisory Board Member) 30 Nov 2022
    Kevin J Black, Departments of Psychiatry, Neurology, Radiology, and Neuroscience, Washington University in St. Louis School of Medicine, St. Louis, 63110, USA
    30 Nov 2022
    Author Response F1000Research Advisory Board Member
    I thank Dr. Pawha for agreeing with my main point and for her thoughtful question about why this article exists. Please let me explain. The raison d'être for this article ... Continue reading
COMMENTS ON THIS REPORT
  • Author Response (F1000Research Advisory Board Member) 30 Nov 2022
    Kevin J Black, Departments of Psychiatry, Neurology, Radiology, and Neuroscience, Washington University in St. Louis School of Medicine, St. Louis, 63110, USA
    30 Nov 2022
    Author Response F1000Research Advisory Board Member
    I thank Dr. Pawha for agreeing with my main point and for her thoughtful question about why this article exists. Please let me explain. The raison d'être for this article ... Continue reading

Comments on this article Comments (0)

Version 2
VERSION 2 PUBLISHED 12 Jul 2022
Comment
Alongside their report, reviewers assign a status to the article:
Approved - the paper is scientifically sound in its current form and only minor, if any, improvements are suggested
Approved with reservations - A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit.
Not approved - fundamental flaws in the paper seriously undermine the findings and conclusions
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