Strict monitoring of lithium levels urged

By Eleanor McDermid, Senior medwireNews Reporter

Plasma levels of lithium above the advised range are associated with a transient reduction in kidney function, research shows.

But Emma Kirkham (University of East Anglia, Norwich, UK) and co-researchers note that the cumulative effects of multiple exposures are not clear.

“[A]s such we suggest that lithium level monitoring should be undertaken at least every 3 months, in line with current UK guidelines, and not be reduced further until the impact of more than one exposure to these lithium levels has been fully established”, they write in BMJ Open.

However, they note that patients are often not monitored as per the guidelines.

Their study included 699 patients identified in a countywide database. The patients were aged between 18 and 96 years, with around half being older than 60 years, and about 60% were women. The cohort reflects real-life practice and is representative of other lithium-taking populations, says the team.

Kirkham et al found a dose-response effect, with plasma lithium levels of 1.01–1.20 mmol/L associated with a 3.88 percentage point reduction in estimated glomerular filtration rate (eGFR) measured within 3 months of the lithium value, while levels of 1.21–2.00 mmol/L were associated with a 5.40 percentage point reduction. These reductions were significant after accounting for age and gender.

The suggested therapeutic range for lithium in the UK is between 0.4 and 1.0 mmol/L, say the researchers. “Levels above 0.8 mmol/L have not only been associated with a limited increase in efficacy, but have also been linked to higher risks of renal toxicity, unwanted side effects and fluctuations of lithium level.”

However, patients’ eGFR appeared to recover, with levels at 6 and 12 months ranging from 0.20 percentage points below baseline to 8.24 percentage points above, irrespective of baseline lithium level.

“A small change in GFR of 5 mL/min in an individual patient may well be due to variability in measurement of plasma creatinine, and is unlikely to lead to any action, unless it was sustained or there was further deterioration, which is another reason for regular monitoring”, note Kirkham and team.

They say that further work is ongoing to establish whether the kidneys recover from multiple exposures to elevated lithium levels.

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