Rapid desipramine dose adjustment using 24-hour levels.

Prior work indicates that plasma tricyclic levels obtained 24 hours after a single dose correlate well with steady state levels achieved. Although this suggests that 24-hour levels could be used to predict the dose needed to reach a desired plasma level, this method has seldom been tested prospectively. In the current study we test this strategy and determine patients' tolerance of rapid dose adjustment. First, the relationship of 24-hour levels and steady state levels in a sample of 16 inpatients was determined using a fixed dose paradigm. In a second sample of 26 depressed inpatients, plasma desipramine levels obtained 24 hours after a single test dose were applied to the regression equation derived from the first sample in order to estimate the dose needed to achieve a steady state level of 140 ng/ml. Once determined, the full dose was then rapidly administered. Sixteen of the 18 (89%) patients who completed the dose adjustment study had steady state drug concentrations within a target range of 125 to 300 ng/ml. This distribution of levels differed significantly from that previously reported for a fixed dose sample in which only 19 of 83 (23%) patients had levels within this range. Dose adjustment using 24-hour levels was well tolerated and should help to attain a more rapid response to antidepressant treatment. This has important implications for reducing lengths of hospitalization for depressed inpatients. The technique should also prove useful in research where a uniform plasma level paradigm is desirable.