Pathology Handbook

Lithium

Synonyms

Priadel, Camcolit, Liskonum

Clinical Indications

Lithium is use in the prophylaxis of mood disorders, specifically depressive illness.  Concentration monitoring is essential when therapy is initiated; once therapy is established, routine monitoring is advocated at 3 to 6 monthly intervals.  For individual patients, serum concentration and dose are linearly related which makes dose adjustment easier.  Thyroid function and creatinine should also be measured at least annually.

Drug Kinetics

Peak absorption occurs within 2-4 hours after oral dose, with complete absorption after 8 hours. Lithium is virtually unbound to plasma proteins and is freely filtered by the glomerulus where it is reabsorbed by the same mechanism as sodium in the proximal tubule.
Half-life varies with age from 8-20 hours in younger patients with normal renal function, increasing to 30-40 hours in the elderly or in patients with impaired renal function.

Request Form 

Request on ICE
Please state time after last dose on request form.

Availability

On request during routine hours. Laboratory must be contacted regarding urgent requests.

Specific Criteria

None

Patient Preparation

Samples should be taken 12 hours after last dose.

Steady state levels are achieved 2-5 days following a change in dose.

Turnaround Time

Daily

Specimen

Serum

Volume

2 ml

Container

Vacutainer gold top

Do not use lithium heparin tubes

Lab Handling

Samples should be analysed same day if left on gel

Causes for Rejection

Unlabelled or incorrectly labelled sample

Collected too soon after last dose

Target Range

0.4 to 1.0 mmol/L. Effective prophylaxis can be achieved in most patients with levels of 0.5 to 0.8 mmol/L at 12 hours post dose. 

Toxicity

Concentrations above 1.4 mmol/L may exertnephrotoxic effects, which leads to decreased elimination and serum levels rise still further. 

Lithium concentrations above 2.5 mmol/L are associated with significant mortality, especially if they arise as a result of gradual build-up on regular therapy rather than acute overdose.

Overdose

In acute cases measure the lithium level at 6 hours and repeat 6-12 hourly. For acute on chronic or chronic accumulation measure the serum lithium concentration immediately and at 6 hours, then repeat 6-12 hourly. Do not use lithium-heparin tubes for the sample.