Renal clearance of lithium rises in pregnancy and falls back after delivery, so a dose that was right in the third trimester can produce a high level postpartum. Fluid shifts, blood loss and reduced intake around delivery add to the risk.
Take trough levels about 12 hours after the last dose, and recheck them in the days after birth and after any dose change. Watch for tremor, vomiting, diarrhoea or confusion as signs of toxicity.
- Take lithium levels as troughs, about 12 hours after the last dose.
- Recheck levels soon after delivery and after any dose change.
- Plan the postpartum dose with the obstetric team before labour.
- Watch for tremor, vomiting, diarrhoea or confusion as early signs of toxicity.
Why it matters
The postpartum fall in clearance turns a stable pregnancy dose into a toxic one without any change in prescription.
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