Lithium carbonate

How it works

Its mood-stabilising action is incompletely understood but involves modulation of second-messenger systems, including effects on inositol monophosphatase and glycogen synthase kinase-3 signalling.

Prescribing in practice

• Lithium has a narrow therapeutic index and serum levels must be monitored, with toxicity precipitated by dehydration, renal impairment, sodium depletion, NSAIDs, diuretics and ACE inhibitors; brands are not interchangeable.
• Long-term use can impair renal and thyroid function and cause hypercalcaemia, so check renal, thyroid and calcium status before and periodically during treatment.
• Recognise toxicity (tremor, vomiting, diarrhoea, ataxia, confusion, seizures) as a medical emergency and counsel on maintaining fluid and salt intake and avoiding interacting medicines.

Monitoring

Monitor serum lithium levels regularly, with periodic renal function, thyroid function and calcium, more often after dose changes or intercurrent illness.

Counselling the patient

• Maintain steady fluid and salt intake and seek advice during vomiting, diarrhoea or fever.
• Carry a lithium record, take blood tests as scheduled, and avoid over-the-counter anti-inflammatory painkillers unless approved.
• Report tremor, drowsiness, slurred speech or vomiting urgently as signs of toxicity.

Evidence & guidelines

NICE bipolar disorder guidance recommends lithium as a first-line long-term treatment with defined serum-level and organ-function monitoring.