[Plasmatic concentrations of fluoxetine, pharmacokinetics, therapeutic response and side effects]

The kinetics of fluoxetine and possible relations between the drug's plasmatic concentration and therapeutic response and side effects were evaluated in a sample of 66 depressive patients, 26 men and 40 women, average age 46.6 years (SD = 14.1), diagnosed according to DSM-III criteria and evaluated using the Hamilton scale for depression (17-item HRSD). We found no difference between plasmatic concentration of fluoxetine in weeks 3 and 6 of treatment, nor in the sum of drug plus active principle in weeks 3 and 6. There was no significant linear correlation between plasmatic concentrations of fluoxetine, norfluoxetine, or the sum of both in weeks 3 and 6 and score on the Hamilton scale in week 6. By means of serial Chi-score calculation we found a "minimum plasmatic concentration" of about 30 ng/ml below which there was less therapeutic response.