Lithium

• Patients should maintain adequate water intake and not reduce Na in their diet

Indications

• prophylaxis in recurrent affective disorder
• acute treatment of mania
• augmentation of antidepressants in refractory depression
  • ~50% patients show useful response at 1-3 weeks
• schizoaffective disorder
• control of aggression

Use

• thyroid function tests
• renal function / U&Es
• contraception for women / pregnancy test
  • teratogen in 1st trimester
• serum lithium levels need monitoring (0.4-1mmol/L) - initially weekly until stable

Monitoring

• Level every 6 months, 8-12 hours after last dose
• aim 0.4 -1.0 mmol/l
• TFT, U&E and Ca once a year

Mechanism of action

• Acts as a 5HT1A agonist so increasing 5HT action in the CNS
• Also acts as 5HT2 antagonist
• PI pathway blockage??
• affects sodium, potassium, calcium and magnesium
• 5HT, noradrenaline, dopamine, acetylcholine systems
• cAMP linked receptors may explain effects on thyroid and kidney

Side effects

• nausea
• fine tremor
• weight gain
• oedema
• polydipsia, polyuria
• exacerbation of psoriasis and acne
• loose bowels
• long term
  • hypothyroidism
  • impaired renal function
  • hypercalcaemia
  • tardive dyskinesia

Overdose

>1.5 mmol/l,  indicated by

• vomiting
• diarrhoea
• coarse tremor
• slurred speech / dysarthria
• ataxia
• drowsiness
• confusion
• convulsions
• coma
• death (>2mmol/L)

Treatment

• cessation of lithium
• forced diuresis (IV mannitol)
• haemodialysis / peritoneal dialysis

Contra-indications

• renal, cardiac, thyroid, 
• Na losing states
  • Addison's disease
  • dehydration / diuretics
• pregnancy, breastfeeding
• Myasthenia gravis
• Operations

Interactions

• Levels increased by diuretics and NSAIDS
• Toxicity (5-HT) increased by 
  • haloperidol
  • SSRIs / venlafaxine 
  • anticonvulsants
• Calcium channel blockers
• antibiotics