the effective dose for geriatric cases is lower for lithium than otherwise. The problem is that levels have to be frequently monitored because the minimum therapeutic level, added to dye for procedures, can be toxic to kidneys. It is probably still worth considering.

The short version: the retrieval confirms that lower serum lithium targets are recommended for older adults, but it does not contain a study of 0.3 mEq/L in CKD stage 2, so the safety question remains unanswered.

The ISBD expert panel recommended target serum lithium of 0.4 to 0.8 mmol/L for ages 60-79 and 0.4 to 0.7 mmol/L for ages 80+, with 100% consensus that lithium is the preferred maintenance monotherapy [1]. Your 0.3 mEq/L level is below even the lower end of that range, which explains the lack of benefit. The same study noted that local laboratories typically report 0.6-1.2 mmol/L as the therapeutic range and none had a separate range for older adults [1], meaning standard lab guidance would have flagged your level as subtherapeutic.

On the renal side, the evidence shows lithium clearly affects kidney function. Long-term lithium treatment significantly reduced urine osmolality and urine-to-serum osmolality ratio compared to lithium-naive controls [4]. A retrospective UK cohort found a twofold increased risk of renal failure and a two-and-a-half-fold increased risk of chronic kidney disease in lithium-treated patients [3]. However, end-stage renal disease was uncommon at 0.5% of patients [3], and in a 2019 study, glomerular markers like cystatin C and NGAL showed no significant impairment versus controls [4]. The same study found that older patients (>50 years) received significantly lower daily lithium doses while maintaining similar serum concentrations [4], consistent with the idea that geriatric dosing should be lower.

The case report of a 73-year-old man on stable lithium who developed severe toxicity (4.2 mmol/L) with acute renal failure shows how quickly things can go wrong, though his level was far above yours [2]. His kidney function recovered to near normal by day 10, but ataxia and dysarthria persisted [2].

My call: the evidence supports that your level was too low for benefit, but it does not answer whether 0.3 mEq/L was safe in CKD stage 2. The renal risks of lithium are real and dose-dependent, but the threshold for harm at very low levels in compromised kidneys is not studied in these records. Confidence: moderate on the lack of benefit, not clear on the safety question.