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.
Abou-Auda
Hisham S
HS
Department of Clinical Pharmacy, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia. hisham@ksu.edu.sa
Al-Yamani
Mohammad J
MJ
Abou-Shaaban
Rafiq R
RR
Khoshhal
Sahal I
SI
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018692:Antimanic Agents / Q000008:administration & dosage* / Q000097:blood / Q000493:pharmacokinetics; D003627:Data Interpretation, Statistical; D004305:Dose-Response Relationship, Drug; D016903:Drug Monitoring / Q000379:methods*; D005260:Female; D006801:Humans; D016014:Linear Models; D016651:Lithium Carbonate / Q000008:administration & dosage* / Q000097:blood / Q000493:pharmacokinetics; D008297:Male; D001523:Mental Disorders / Q000188:drug therapy*; D008875:Middle Aged; D011237:Predictive Value of Tests
D018692:Antimanic Agents; D016651:Lithium Carbonate