Use of saliva lithium determinations for monitoring lithium therapy

During acute and chronic administrations of lithium, 25 patients were studied to determine the effect of other psychotropic drugs on the plasma-saliva lithium concentration correlations. Changes, even discontinuation, in either tricyclic antidepressants or neuroleptics did not affect the plasma-saliva ratio which had an overall correlation coefficient of r = 0.79 (p less than 0.01). The relationship using linear regression analysis was described by the equation, y = 2.27x--0.45. Individual patients' plasma-salivary relations were described by this equation in 87% of cases. The study extends the usefulness of these determinations to include patients on lithium and neuroleptics or tricyclic antidepressants.