Bioequivalence study of fluoxetine hydrochloride in healthy volunteers.

Fluoxetine hydrochloride (CAS 59333-67-4) is a selective serotonin reuptake inhibitor (SSRI) widely used as antidepressant drug. The aim of the present trial was to assess the bioequivalence of a new formulation of the drug (test formulation) as compared to a reference product from the Swiss market. Both drugs were available as 20 mg dispersible tablets. The trial was performed according to a two-period, two-sequence, balanced, randomised, single-dose design with a wash-out phase of at least 56 days. The two formulations were tested in 30 male healthy volunteers. A specific highly sensitive bioassay in tandem mass spectrometry allowed to set the limit of quantification to 100 pg/ml for fluoxetine and norfluoxetine. Average t(max) was 5.4 h for fluoxetine and 71-80 h for norfluoxetine. The peak concentration was on average 14 ng/ml for fluoxetine and 10.5 ng/ml for norfluoxetine. Half-life was on average 48-50 h for fluoxetine and 130-138 h for norfluoxetine. AUC infinity for fluoxetine and norfluoxetine were on average 790 and 2800 ng x ml(-1) x h, respectively. All these figures demonstrate that plasma concentration-time profiles of fluoxetine and norfluoxetine are quite different. Applied statistical tests, suggested by operating guidelines, demonstrated bioequivalence of the test formulation and the reference formulation. The conclusion on bioequivalence was based on both fluoxetine and norfluoxetine results. 90 % confidence Intervals for Cmax, AUCt and AUC infinity (fluoxetine and norfluoxetine) were within the acceptance range (0.80-1.25) and t(max), processed with a non-parametric test, did not show any statistically significant difference between test and reference formulation. Safety and tolerability proved to be similarly good with both test and reference formulation. In conclusion, the present trial has demonstrated bioequivalence of the test and the reference formulation, both consisting of fluoxetine hydrochloride dispersible tablets.