Lithium clinical response time

An initial determination of serum lithium concentration should be obtained about 5 days after the start of treatment, at which time steady-state conditions should have been attained. If the clinical response suggests a change in dosage, simple arithmetic (new dose equals present dose times desired blood level divided by present blood level) should produce the desired level. The serum concentration attained with the adjusted dosage can be checked after another 5 days. Once the desired concentration has been achieved, levels can be measured at increasing intervals unless the schedule is influenced by intercurrent illness or the introduction of a new drug into the treatment program. 

The advantages for the psychiatrist are that time is saved because only one interview is required. Doubtful or disputed results can be repeated immediately and patients who have defaulted on treatment can face this with confidence. Changes in medication may be more rapidly monitored and, in the initial stages of lithium treatment, the time taken to attain optimum plasma lithium can be reduced because the new dose can be instigated as soon as possible. The response from our collaborating clinicians has been very positive and we are developing the procedure for wider acceptance [86,87]. This analytical advance may prove to be one of the most important improvements to be made in the clinical use of lithium in the immediate future [60]. 

Development of lithium selective electrodes (LiSE) and their application in clinical chemistry have been amply reviewed Several models of lithium ion specific electrodes are commercially available. The central problems in developing such sensing devices are their dynamic range, the accuracy and precision by which the signals are correlated to the concentration of the analyte and the selectivity towards that species, especially in relation to other alkali metal cations. Additional problems of practical importance are the times of response and recovery and the durability of the electrode in the intended service. 

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