Best Tests March 2007
|Full colour PDF of ‘best tests’ March 2007.
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Biochemical Monitoring of Lithium Therapy
Recently in ‘Best Practice Journal’ we provided an overview and guidance on the management of patients taking lithium. Reproduced below is an edited version of laboratory tests usually recommended for the routine monitoring of a patients on lithium. For the full text visit www.bpac.org.nz/magazine/2007/february/lithium.asp
|Lithium levels||3-monthly||Monitor more frequently in high risk patients, e.g. those on potentially interacting drugs, poor compliance, elderly, unstable renal function, physical illness|
|Thyroid Function||TSH 3 months after initiation and then 6-monthly||T4 not routinely required. Monitor for symptoms of hypothyroidism|
|Electrolytes||Check with lithium serum levels every 3 months||Particularly important to monitor sodium as it competes for reabsorption in proximal renal tubule|
|Renal function||Check at same time as lithium levels, at least every 3 months||Estimate renal function using the Cockcroft and Gault Equation* based on ideal body weight|
|Serum calcium and magnesium||Check every 2 years||Lithium may rarely cause hypercalcaemia and hypermagnesium|
|Parathyroid Hormone (PTH)||Measure only if serum calcium is elevated. PTH must be interpreted relative to serum calcium measurement on the same specimen|
|*The bpac creatine clearance calculator is based on the Cockroft-Gault equation|
Reference: bpacnz. Lithium in General Practice. BPJ 2007;3:16–27.