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Using this page · Individualise medicines monitoring

This medicines monitoring page has been written using publications and expert opinion. It is designed to save clinician time, but not replace professional responsibility. When using this page you should: ensure an individualised monitoring plan is developed in partnership with the patient and take account of any locally agreed advice and guidance.

Before starting

Required

  • Baseline
    • Body weight or Body mass index
    • Cardiac functionespecially in patients with cardiovascular disease or at risk who may require ECG.
    • Estimated glomerular filtration rate
    • Serum calcium
    • Thyroid function testspatients should be euthyroid before initiation
    • Urea and electrolytes

After started or dose changed

Required

  • At one week; then weekly until levels stable; then every 3 months for first year
    • Lithium levelstake sample just prior to time of next dose (i.e. trough level 12 hours following last dose)

Ongoing once stable

Required

  • Every 3 - 6 months
    • Lithium levelstake sample just prior to time of next dose (i.e. trough level 12 hours following last dose)
  • 6 monthly
    • Body weight or Body mass index
    • Estimated glomerular filtration rate
    • Serum calcium
    • Thyroid function tests
    • Urea and electrolytes

Monitor lithium levels more frequently in high risk patients

More frequent monitoring (at least 3 monthly) may be required in the following patients:

  • Age 65 years and older
  • Taking drugs that interact with lithium
  • Risk of impaired renal function: e.g. eGFR declines over two or more tests; or urea and creatinine elevated
  • At risk of impaired thyroid function
  • Raised calcium levels or other complications
  • Significant change in a patient’s sodium or fluid intake
  • Have poor symptom control or poor adherence
  • The last serum-lithium concentration was 0.8 mmol/litre or higher

Abnormal results

Risk of toxicity

Lithium toxicity occurs at serum lithium concentrations of approximately 1.5 mmol/L and above, but may occur despite an apparently normal plasma level. The risk of toxicity is greater in people with hypertension, diabetes, congestive heart failure, chronic renal disease, schizophrenia, Addison’s disease, and COVID-19.

Signs and symptoms

Signs of lithium toxicity include increasing diarrhoea, vomiting, anorexia, muscle weakness, lethargy, dizziness, ataxia, lack of coordination, tinnitus, blurred vision, coarse tremor of the extremities and lower jaw, muscle hyper-irritability, choreoathetoid movements, dysarthria, and drowsiness.

Action required

If lithium toxicity is suspected, do an urgent lithium level immediately and seek specialist advice.

For patients with symptoms of lithium toxicity (e.g. diarrhoea, vomiting, tremor, mental state changes, or falls):

  • withold lithium
  • take urgent serum lithium level and U&Es
  • seek specialist advice

Referral to secondary care may be required depending on the severity of symptoms and the certainty of toxicity. Use clinical judgement to determine the urgency of referral.

Renal function

Monitor dose and blood levels more closely and assess the rate of renal function deterioration in the following circumstances:

  • Elevated urea levels
  • Elevated creatinine levels
  • Decline in eGFR

Notes

Advice to patients

Advise patients to maintain adequate fluid intake and avoid dietary changes which reduce or increase sodium intake. Advise patients to avoid taking NSAIDs over the counter.
Advise patients to report signs and symptoms of:

  • lithium toxicity
  • hypothyroidism
  • renal dysfunction (including polyuria and polydipsia)
  • benign intracranial hypertension (persistent headache and visual disturbance)

Prescribing by brand

Preparations vary widely in bioavailability and therefore should be prescribed by brand. Switching from one brand or preparation to another preparation requires the same precautions as initiation of treatment.

Bibliography

Enquiries about this page

Contact us if you have any enquiries about the drug monitoring information on this page.