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Renal replacement therapy associated with lithium nephrotoxicity in Australia

To the Editor: Adam1 contends that Roxanas and colleagues2 have overemphasised the risk of renal replacement therapy (RRT) associated with lithium treatment. I disagree.

Lithium nephrotoxicity appears to require about a decade of treatment to develop3 and a further 10–20 years before RRT is necessary.3,4 Adam inappropriately divides the number of incident cases of RRT attributed to lithium use by the number of patients currently taking lithium. Rather, cumulative incidence estimates for RRT derived from cohort studies are required.5

Adam calculates that the risk of RRT due to lithium use is lower in Australia than in Sweden, but he uses prevalent cases from Sweden and incident cases from Australia. I calculate that, over a 5-year period, the average annual incident rate of RRT attributed to lithium use per million population is 0.82 in Sweden (95% CI, 0.41–1.47)3 compared with 0.78 in Australia (95% CI, 0.67–0.90).2 The current prevalence of lithium prescribing is also similar — 1150 per million in Australia2 and 1255 in Sweden3