Prediction of steady-state imipramine and desmethylimipramine plasma concentrations from single-dose data

Tricyclic antidepressant plasma levels were measured in patients and healthy subjects after a single dose of desmethylimipramine (DMI) or imipramine (IMI) and after chronic dosing to steady states. Tricyclic plasma levels measured 24 hr after the single oral dose correlated with steady-state plasma levels. In patients receiving DMI there was a correlation (r = 0.97, n = 10) between 24-hr and steady-state DMI levels, while in normal subjects receiving IMI the correlation was r = 0.92 (n = 20) between 24-hr and steady-state total tricyclic levels (IMI plus its metabolite, DMI). These results suggest the possibility that after a test dose of tricyclic antidepressant, a patient may be put on a "therapeutic" dosage regimen without delay.