A comparison of pharmacokinetic versus empirical lithium dosing techniques

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.

A new accurate method for predicting lithium clearance and daily dosage requirements in adult psychiatric patients

OBJECTIVE

The present study aimed to derive new equations for estimating lithium clearance and daily dosage requirements needed to achieve an intended lithium serum level for adult psychiatric inpatients and outpatients.

METHODS

Data were retrospectively collected from 60 adult psychiatric patients (34 males and 26 females, aged between 18-80 years) in both inpatient and outpatient settings. All variables that might affect lithium clearance and/or lithium serum concentration were included and analyzed by stepwise multiple linear regression to produce equations describing lithium clearance and daily dosage requirements for these patients. The validation of the developed equations was performed by application to another 60 psychiatric subjects in both the inpatient and outpatient settings. The bias and accuracy of the new methods were also compared to those set forth by the empirical method and the a priori methods developed by Zetin, Pepin, Jermain and Terao and colleagues.

RESULTS

The following prediction equations for lithium clearance (CL(Li)) were obtained: CL(Li) (inpatients) = 0.932 + 0.185CL(Cr) and CL(Li) (outpatients) = 1.021 + 0.141CL(Cr). The equations derived for daily dosage requirements were: daily dose (inpatients, mg) = 350.15 + 289.92 (desired lithium level, mmol/L) + 0.84 (weight, kg) - 1.76 (age, years) + 34.43 [tricyclic antidepressant (TCA), yes = 1, no = 0] + 62.1(CL(Cr), L/h) + 13.1 [blood urea nitrogen (BUN), mmol/L] + 40.9 (sex, male = 1, female = 0) and daily dose (outpatients, mg) = 784.92 + 530.22 (desired lithium level, mmol/L) + 8.61 (weight, kg) - 12.09 (age, years) - 11.14 (TCA, yes = 1, no = 0) - 7.63 (CL(Cr), L/h) - 42.62 (BUN, mmol/L) - 23.43 (sex, male = 1, female = 0). In the present method, the prediction error for clearance was 10.31% and 6.62% for inpatients and outpatients, respectively, and the prediction error for daily dosage requirements was 3.96% and 2.95% for inpatients and outpatients, respectively.

CONCLUSIONS

Compared to previously reported methods, the present method proved to be accurate and can be safely used for the prediction of lithium clearance and daily dosage requirements in psychiatric inpatients and outpatients.

Comparison of lithium dosage methods for preschool- and early school-age children

OBJECTIVE

Lithium may be useful in the treatment of prepubertal children with bipolar disorder or aggressive conduct disorder. However, there are few dosage guidelines. This study compares two dosage methods reported for prescribing lithium to prepubertal children: (1) a weight-based dosing schedule and (2) a single-dose, kinetics-based method.

METHOD

Lithium doses were calculated using each method and then compared with doses actually used in the clinical care of hospitalized children.

RESULTS

No statistically significant differences were found between mean lithium dose estimates calculated by the two methods. Average lithium dose estimates for both kinetic and weight-based methods were less than the observed discharge doses. Differences were seen between the two methods for children weighing between 25 and 30 kg.

CONCLUSIONS

The weight-based dosing schedule and the single-dose, kinetics-based methods for calculating lithium dose result in similar dosage estimates when applied to young children.

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.