Abstract
Lithium is viewed as the first-line long-term treatment for prevention of relapse in people with bipolar disorder. This study examined factors associated with the likelihood of maintaining serum lithium levels within the recommended range and explored whether the monitoring interval could be extended in some cases. We included 46 555 lithium rest requests in 3371 individuals over 7 years from three UK centres. Using lithium results in four categories (<0.4 mmol/L; 0.40-0.79 mmol/L; 0.80-0.99 mmol/L; ≥1.0 mmol/L), we determined the proportion of instances where lithium results remained stable or switched category on subsequent testing, considering the effects of age, duration of lithium therapy and testing history. For tests within the recommended range (0.40-0.99 mmol/L categories), 84.5% of subsequent tests remained within this range. Overall, 3 monthly testing was associated with 90% of lithium results remaining within range, compared with 85% at 6 monthly intervals. In cases where the lithium level in the previous 12 months was on target (0.40-0.79 mmol/L; British National Formulary/National Institute for Health and Care Excellence criteria), 90% remained within the target range at 6 months. Neither age nor duration of lithium therapy had any significant effect on lithium level stability. Levels within the 0.80-0.99 mmol/L category were linked to a higher probability of moving to the ≥1.0 mmol/L category (10%) compared with those in the 0.4-0.79 mmol/L group (2%), irrespective of testing frequency. We propose that for those who achieve 12 months of lithium tests within the 0.40-0.79 mmol/L range, the interval between tests could increase to 6 months, irrespective of age. Where lithium levels are 0.80-0.99 mmol/L, the test interval should remain at 3 months. This could reduce lithium test numbers by 15% and costs by ~$0.4 m p.a.
Highlights
Lithium is viewed as the first-line long-term treatment for prevention of relapse in people with bipolar disorder
The efficacy of lithium treatment in reducing relapses in bipolar disorder was confirmed in the largest randomised controlled trial of lithium for maintenance treatment of bipolar disorder to date.[4]. This showed that in patients stabilised on quetiapine during an acute phase of bipolar disorder, switching to lithium significantly increased time to recurrence of any mood, manic or depressive event compared with switching to placebo
Results in the recommended therapeutic range (0.40–0.99 mmol/L) were defined as ‘within accepted range’. For those patients whose current results were within accepted range, we examined the associations of (a) patient age, (b) duration of lithium treatment and (c) result history within the previous 12 months with the proportion of tests that remained within accepted range at subsequent testing
Summary
Lithium was first found to have an acute antimanic effect in 1948,1 with further corroboration in the early 1950s.2 It took some time for lithium to become the standard treatment for relapse prevention in bipolar affective disorder, following the publication of early trials of lithium treatment in the 1960s.3 It was licensed for use in bipolar disorder by the US Food and Drug Administration in 1970. It took some time for lithium to become the standard treatment for relapse prevention in bipolar affective disorder, following the publication of early trials of lithium treatment in the 1960s.3. It was licensed for use in bipolar disorder by the US Food and Drug Administration in 1970. Lithium is viewed as the first-line long-term treatment for prevention of relapse and hospital admission in people with bipolar disorder and is recommended by the UK National Institute for Health and Care Excellence (NICE)[5] as well as in clinical practice guidelines in the USA, Canada, Japan, The Netherlands, Australia and New Zealand, and by the International Society for Bipolar Disorders.[6,7,8] Lithium has other roles in psychiatry, including as an augmenting agent to antidepressants in unipolar depression.[9]. We used request data for clinical laboratory serum lithium tests collected from three large UK centres with varying approaches to managing patients with bipolar disorder and ordering lithium testing
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