Saliva and Serum Lithium Monitoring in Hospitalized Patients and Possibility to Replace Serum to Saliva

The lithium ions concentration in human serum and saliva was determined using dry-slide technology Vitros 250 Analyser (Ortho Clinical Diagnostic) and atomic absorption spectrometry Perkin Elmer 403 (AAS). We analyzed lithium ions in 100 serum and saliva specimens of patients after oral administration of lithium carbonate (3 x 300 mg) Jadran, Galen Laboratory Rijeka. Saliva and blood were taken 2 and 12 hours after the last dose. At the same time lithium ions at samples of blood and saliva were determined with both methods which showed high level of correlation. The mean difference of lithium ions between saliva and serum was statistically significant for p<0.05 using t student test. At saliva we got constant of elimination Kel = 0.02(-1)h and elimination half life (t(1/2)) was t(1/2)=34.6 h. For serum was t(1/2)= 24 h what means that lithium ions elimination is slower from saliva then from serum. That is the reason why probably concentration at saliva is higher then at serum. Lithium elimination is two compartment pharmacokinetic model where important part of compartment are saliva and salivary glands. At a certain point in medical treatment it could be expected to use controlled determination of lithium ions in saliva with serum as control.