Relationship between patient variables and lithium dosage requirements.

The relationships between several patient variables and lithium dosage requirements were determined in 71 inpatients receiving a slow-release lithium product. Age, weight, ideal body weight, sex, body surface area, creatinine clearance, presence of depression, concurrent use of tricyclic antidepressants, and acuteness of symptoms were significantly related to dosage requirements. The contribution of each factor to dosage requirements was further defined using multiple regression analysis and used to assess a published patient variable-based lithium dosing technique. Addition to that model of information concerning presence of depression, acuteness of symptoms, and creatinine clearance minimally improved predictability. The published model is recommended as an alternative to empiric methods.