The lithium loading dose method in a clinical setting

How to initiate lithium therapy: a systematic review of dose estimation and level prediction methods

BACKGROUND

Throughout the past decades, several methods have been developed to achieve therapeutic lithium blood levels as quick and safe as possible. The present study will systematically review the methods developed and studied for lithium dose estimation or level prediction at the initiation of therapy.

METHODS

A systematic computerized Medline search was performed for papers published in English, French or Dutch between 1966 and April 2012 describing or studying methods for dosing lithium or predicting the lithium level on a certain dosage. References of relevant articles were screened for additional papers.

RESULTS

Of 273 unique references retrieved, 65 met the inclusion criteria. Apart from the empirical titration method, 38 predictive methods for initiating lithium were identified. These methods can be classified into two categories: the a priori predictive methods, and the test-dose predictive methods requiring the administration of a test dose of lithium prior to starting treatment.

LIMITATIONS

The methodological strength was not taken into account for a study to be included in the review.

CONCLUSIONS

The most important distinction between the empirical titration method and the predictive methods appears to be the shorter time the latter need to achieve the targeted lithium level. The vast majority of predictive methods, however, show inconsistent or poor results or have not been replicated since their initial description. The empirical titration method, although not extensively studied, appears to be a time-honored method that can be recommended for use in daily clinical practice.

Preliminary comparison of predictive and empiric lithium dosing: impact on patient outcome

OBJECTIVE

To evaluate whether initiating lithium with predictive dosing compared with empiric dosing improves outcome in patients with manic symptoms.

DESIGN

The study was a randomized, single-blind design and used the Modified Slattery predictive method.

SETTING AND PARTICIPANTS

Eighteen inpatients at an urban psychiatric hospital with a Mania Rating Scale (MRS) score greater than or equal to 24 were enrolled.

OUTCOME MEASURES

The study endpoint was defined as an MRS rating less than or equal to 14 or discharge from the hospital. Assessments (MRS, Brief Psychiatric Rating Scale, Clinical Global Impression, Systematic Assessment for Treatment of Emergent Events Scale, quality of life measures) were completed at baseline, on days 3 or 4 and 7 or 8, and weekly thereafter.

RESULTS

The predictive group achieved a therapeutic concentration significantly sooner than did the empiric group (p = 0.004); however, the mean serum lithium concentration at discharge did not differ between the groups. The predictive group was taking significantly higher dosages of antipsychotics in chlorpromazine equivalents on day 3 or 4 (p = 0.05). Significantly fewer gastrointestinal/genitourinary adverse effects on day 3 or 4 were reported by patients in the predictive group (p = 0.04). No difference was found between groups with any rating scale or other pharmacokinetic or medication item. Even though the difference did not meet statistical significance, the predictive group's length of stay in the acute unit was three days shorter than that of the empiric group, which may represent significant cost savings.

CONCLUSIONS

The preliminary data do not suggest that patient outcome is improved by using Modified Slattery predictive dosing; however, the suggestion of a shorter length of stay in a restrictive unit merits further evaluation.

Drug dose prediction with flexible test doses

This article presents the first known practical method to apply one-compartment pharmacokinetic modeling to prediction of doses for drugs from one or more blood-drug concentrations, without requiring approximations or a computer. It should be useful for regulating doses of orally administered CNS drugs whose effects develop over a day or more, e.g., lithium, antidepressants, and anticonvulsants. Pharmacokinetic calculations for sequences of one, two, and three test doses are condensed into graphs that can be rapidly applied for clinical purposes. These graphs account for dose division, blood sampling time, and drug elimination rate; they show that the ratio of the steady-state day-mean drug level to the test-drug blood level is independent of the half-life if the test level is about a day after the last test dose. The calculations show the same value as experimental measurements for the ratio between steady-state serum lithium level and serum lithium level measured after a test dose. A rational strategy for drug-loading doses is discussed.

The effects of lithium carbonate on healthy volunteers: mood stabilization?

A 2-month lithium-placebo double-blind cross-over study was carried out with 17 healthy volunteers. Their mood was self-rated: twice daily (AM, PM) with the Visual Analogue Mood Scale (VAMS); weekly with the analogue scales for subjective states and body symptoms; and three times (basal and at the end of each treatment period) with the Profile of Mood States (POMS). Memory and reaction time were also assessed, but did not show any change. The mean VAMS score decreased during lithium treatment, but the mean mood variability, a measure of the mean successive differences between consecutive mood ratings (delta squared), did not change significantly. There was a tendency toward decreased mood variability on lithium, both during the full 1-month treatment period and in the last week of treatment, when all volunteers had a lithium serum level ranging from 0.6 to 1.0 mEq/liter. The lower mean VAMS scores on lithium could be attributed to lithium-induced dysphoric mood as recorded on the analogue scales and POMS. However, very large inter- and intraindividual differences in response to lithium were observed. Actually, lithium even had an opposite effect on some volunteers' mood. The data and problems involved with assessment of mood and its changes are discussed.

A review of lithium dosing methods

Lithium's narrow therapeutic range, concentration-effect relationship, and large differences in interindividual disposition make it an attractive candidate for predictive dosing methods. Lithium disposition is influenced by a number of factors, including patient characteristics, renal function, and concomitant drug therapies. These factors are accounted for, in varied degrees, in the different dosing methods available. One a priori method takes many of these factors into account and appears to have better reliability than others that ignore nonrenal influences on lithium disposition. The lack of data on pharmacokinetic values in different populations limits the usefulness of many of the single-point methods. Better data on the disposition of lithium in differing populations would greatly enhance the utility of both the a priori and single-point methods. Several multipoint methods, which estimate an individual's pharmacokinetic values, have also been described. These appear to be the most reliable, although they are time consuming and may delay the initiation of therapy. A well-designed Bayesian approach to the dosing of lithium, although not currently available, would be the most useful.

Method for prediction of serum lithium levels

A new computer-assisted method for predicting lithium levels and consulting dosage of lithium is demonstrated. The method is based on a mathematical model describing elimination of lithium after lithium treatment of any duration and regularity. From two values of serum concentration of lithium obtained during a single day, parameters of the model are computed and used for prediction. In an evaluation study involving 20 inpatients, the results demonstrated a high correlation between predicted and observed levels (r = 0.80) and revealed no systematic error of prediction. The elimination rate of lithium in these patients was unrelated to age or to duration of previous lithium therapy.