Psychiatry/Mood stabiliser

Lithium

also: mood stabiliser · bipolar · lithium toxicity

Overview

First-line mood stabiliser for bipolar — narrow therapeutic index, so levels and organ monitoring are mandatory, and the interaction/toxicity list is heavily examined.

Mechanism

Mechanism not fully understood — modulates second-messenger systems (inositol monophosphatase, GSK-3) to stabilise mood. Renally excreted, so anything reducing renal clearance (or sodium/volume) raises levels.

Indications

Bipolar disorder (prophylaxis + acute mania)
Augmentation in resistant depression

Adverse effects

Lithium toxicityserious

Coarse tremor, ataxia, dysarthria, confusion, seizures, renal failure — levels >1.5; precipitated by dehydration/NSAIDs/diuretics/AKI.

Hypothyroidism + hyperparathyroidism (↑Ca)serious

Nephrogenic diabetes insipidus / chronic kidney injuryserious

Fine tremor, weight gain, GI upsetcommon

Teratogenic — Ebstein's anomalyserious

Cardiac malformation if used in pregnancy.

Cautions & contraindications

NSAIDs, thiazides, ACE inhibitors/ARBsall

Reduce lithium excretion → toxicity.

Dehydration / AKI / sodium depletionall

Raises levels.

Pregnancy (esp. 1st trimester)pregnancy

Ebstein's anomaly.

Interactions

NSAIDs / thiazides / ACEi-ARB / metronidazole raise levels
Sodium balance — keep hydration/salt intake stable

Monitoring & kinetics

Levels (0.4–1.0): 12 h post-dose; weekly after a change until stable, then every 3 months,TFTs + U&E + calcium every 6 months

Oral; narrow index. Counsel re hydration, signs of toxicity, and consistent salt intake.

Choosing it

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Source: NICE CG185 — Bipolar disorder · BNF — Lithium