The Anxious Physicist

Personal blog of Dr Alex Mendelsohn

Tag: pharmacokinetics

How I found Amdisen’s original research papers

July 3, 2023 /

Alex describes his experience of taking lithium and his search for information on its pharmacokinetic properties. He wanted to calculate his peak serum concentration and find out his approximate lithium half-life using the exponential decay formula. However, he found that there was no semi-log plot in the literature and no mention of the dual half-life of lithium. He searched for papers on simulations of the pharmacokinetic curve and found references to multi-compartmental models. Eventually, he found a chapter on lithium pharmacokinetics in a book and learned that the two half-lives he observed corresponded to the alpha and beta phases of lithium removal from blood vessels after peak concentration, which could be described using multicompartment models.

When I first started to take lithium, I wanted to calculate my peak serum concentration using my 12-hour sample value. I knew it was going to be a very rough estimation, but for me, doing the calculation made me feel less anxious about toxicity.

My plan was to use the exponential decay formula 1 to find the peak concentration (assuming the peak occurred around five hours). I wanted to find out, given I knew my serum creatinine levels, what my approximate lithium half-life was. I went looking for data in the lithium pharmacokinetic literature to figure this out.

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How imprecise language can lead to the loss of scientific knowledge: part 2

May 19, 2023 /

This blog post is in reference to my article in the May 2023 edition of the Lancet Psychiatry – Lithium Story: Eight Guidelines, Eight Recommendations. It is adapted from notes I sent to one of the editors when constructing the article

The blog post discusses the issue of imprecise language in scientific literature, specifically in the context of lithium pharmacokinetics. Alex provides two examples of unclear messaging from the literature and suggests solutions to improve clarity. Example 3 involves the lack of specificity about the timing of serum concentration values mentioned in a paper by Grandjean and Aubry, while Example 4 highlights a graph by R Hunter that is misleading due to the use of two scales on the x-axis and unclear labelling of subjects. Alex suggests that authors should provide clear and concise statements to remove ambiguity in their writing and improve the accuracy of their research.

In a previous blog post, I looked at two examples of imprecise language in a Grandjean and Aubry paper about lithium pharmacokinetics (which I used in my May 2023 Lancet Psychiatry article). In this post, to show that the problem is not limited to a single paragraph in a single review paper, I have included a couple more examples of unclear messaging.

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