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Question answered:18/03/08
The BNF No. 55, issued this month, gives the following information on lithium serum concentrations:
“Lithium salts have a narrow therapeutic/toxic ratio and should therefore not be prescribed unless facilities for monitoring serum-lithium concentrations are available. There seem few if any reasons for preferring one or other of the salts of lithium available. Doses are adjusted to achieve serum-lithium concentration of 0.4–1 mmol/litre (lower end of the range for maintenance therapy and elderly patients) on samples taken 12 hours after the preceding dose. It is important to determine the optimum range for each individual patient.” [1]
The SPC for Camcolit gives the following monitoring information for patients on maintenance therapy:
“Adults: (Including unipolar mania & unipolar depressions and bipolar manic-depressive illness): A low dose of 300-400 mg of lithium carbonate can be administered daily for the first seven days. A blood sample for plasma lithium estimation is then taken 12 hours after the last dose, and the dosage of Camcolit is adjusted to keep the plasma lithium level within the range of 0.4-0.8 mmol/l. Toxic symptoms are usually associated with concentrations exceeding 1.5 mmol/l.” [2]
Concerning the management of patients with increased levels of creatinine, we could find only general information on the monitoring of patients on lithium. The 2006 NICE guideline recommends:
“1.6.2.10 For patients with bipolar disorder on lithium treatment, prescribers should do the following.
• Monitor serum lithium levels normally every 3 months.
• Monitor older adults carefully for symptoms of lithium toxicity, because they may develop high serum levels of lithium at doses in the normal range, and lithium toxicity is possible at moderate serum lithium levels.
• Monitor weight, especially in patients with rapid weight gain.
• Undertake more frequent tests if there is evidence of clinical deterioration, abnormal results, a change in sodium intake, or symptoms suggesting abnormal renal or thyroid function such as unexplained fatigue, or other risk factors, for example, if the patient is starting medication such as ACE inhibitors, non-steroidal anti-inflammatory drugs, or diuretics.
• Arrange thyroid and renal function tests every 6 months, and more often if there is evidence of impaired renal function.
“Initiate closer monitoring of lithium dose and blood serum levels if urea and creatinine levels become elevated, and assess the rate of deterioration of renal function. The decision whether to continue lithium depends on clinical efficacy, and degree of renal impairment; prescribers should consider seeking advice from a renal specialist and a clinician with expertise in the management of bipolar disorder on this.” [3]
Given the relative lack of specific recommendations on the management of raised creatinine levels resulting in a decreased eGFR in patients on lithium treatment, the NLH Primary Care Q & A Service can only advice seeking advice from a local specialist on this issue.
References
1. BNF No. 55. March 2008. (http://www.bnf.org.uk/bnf/bnf/55/3281.htm?q=%22lithium%22)
2. SPC. CamColit. October 2006. (http://emc.medicines.org.uk/emc/industry/default.asp?page=displaydoc.asp&documentid=1239)
3. NICE. Bipolar disorder. July 2006. (http://www.nice.org.uk/nicemedia/pdf/CG38niceguideline.pdf)
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