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Lithium

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Anna Lee & Charles Gomersall

Updated June 2006

Mode of poisoning

  • most cases due to unintentional overdose during chronic therapy
    • often precipitated by volume depletion and renal inufficiency
  • acute intentional overdose also common

Pharmacokinetics

  • rapidly absorbed from GI tract
  • virtually no protein binding and low volume of distribution (0.7-1 l/kg)
  • small molecule (molecular weight 74 daltons)
  • eliminated by glomerular filtration but 80% reabsorbed in tubules, even more if patient dehydrated
  • elimination half-life ~18 h
    • prolonged in elderly and patients on chronic therapy

Clinical features

  • clinical features varied and many. Severe poisoning may result in permanent neurological damage in 10% of patients. Serum levels following acute ingestion correlate poorly with intracellular concentrations and clinical symptoms. Closer correlation in chronic and acute on chronic toxicity. Severe toxicity may occur at a lower serum concentration in chronic ingestion than in acute overdose
    • mild intoxication (serum lithium 1.5-2.5 mmol/l)
      • tremor, ataxia
      • nystagmus
      • choreoathetosis
      • photophobia
      • lethargy
    • moderate intoxication (serum lithium 2.5-3.5 mmol/l)
      • agitation
      • fascicular twitching
      • confusion
      • nausea, vomiting, diarrhoea
      • cerebellar signs
    • severe toxicity (>3.5 mmol/l)
      • seizures, coma
      • cardiovascular instability
        • sinus bradycardia
        • hypotension
        • decreased anion gap (<6 mEq/l)
  • chronic toxicity includes nephrogenic DI, renal failure, hypothyroidism and leukocytosis

Treatment

  • gastric lavage
  • poorly adsorbed by activated charcoal which is not indicated in absence of co-ingestion of other drugs
  • majority of patients respond to general supportive measures
  • haemodialysis or haemofiltration for:
    • serum levels >3.5 mmol/l  in acute ingestion
    • serum level >2.5 mmol/l in chronic ingestion, symptomatic patients or patients with renal insufficiency
    • serum level <2.5 but following large ingestion so that rising levels expected
    • serum level 1.5-2.5 mmol/l  in any patients with renal insufficiency, severe neurological symptoms or unstable hemodyanmics

    • serum level < 1.5 mmol/l in patients with end-stage renal failure, or following large ingestion so that rising levels expected

    Hemodialysis is more effective than hemofiltration. Problems of rebound toxicity after discontinuation of HD due to tissue redistribution, which can be prevented by either extending the dialysis therapy to 8-12 hours, or initiating CVVH

 ©Anna Lee & Charles Gomersall, June 2006

©Charles Gomersall, April, 2014 unless otherwise stated. The author, editor and The Chinese University of Hong Kong take no responsibility for any adverse event resulting from the use of this webpage.
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