Drug-excipient compatibility testing using a high-throughput approach and statistical design.

The aim of our research was to develop a miniaturized high throughput drug-excipient compatibility test. Experiments were planned and evaluated using statistical experimental design. Binary mixtures of a drug, acetylsalicylic acid, or fluoxetine hydrochloride, and of excipients commonly used in solid dosage forms were prepared at a ratio of approximately 1:100 in 96-well microtiter plates. Samples were exposed to different temperature (40 degrees C/ 50 degrees C) and humidity (10%/75%) for different time (1 week/4 weeks), and chemical drug degradation was analyzed using a fast gradient high pressure liquid chromatography (HPLC). Categorical statistical design was applied to identify the effects and interactions of time, temperature, humidity, and excipient on drug degradation. Acetylsalicylic acid was least stable in the presence of magnesium stearate, dibasic calcium phosphate, or sodium starch glycolate. Fluoxetine hydrochloride exhibited a marked degradation only with lactose. Factor-interaction plots revealed that the relative humidity had the strongest effect on the drug excipient blends tested. In conclusion, the developed technique enables fast drug-excipient compatibility testing and identification of interactions. Since only 0.1 mg of drug is needed per data point, fast rational preselection of the pharmaceutical additives can be performed early in solid dosage form development.

Selective liquid chromatographic method for determination of fluoxetine in plasma.

A selective and sensitive liquid chromatographic method was developed for the determination of fluoxetine (FLU) in plasma. FLU was isolated from plasma by liquid-liquid extraction. The chromatographic separation was performed on an analytical 250 x 3.9 mm id Novapak C18 column (4 microm particle size) with an isocratic mobile phase consisting of phosphate buffer-acetonitrile-methanol -triethylamine (58 + 30 + 10 + 2, v/v) adjusted to pH 7. Using UV detection at 226 nm, the detection limit for FLU in plasma was 3 ng/mL. No interferences were found with tricyclic antidepressant drugs, which allows this method to be used in clinical studies. The calibration curve was linear over the concentration range of 10-200 ng/mL. The average recovery was about 80% for plasma. The inter- and intraday assay coefficients of variation were <8%.

Analytical methods for the quality control of Prozac capsules.

Some analytical methods (two spectrophotometric and two chromatographic procedures) for the determination of fluoxetine in Prozac capsules are described. All of them are applied to the samples after extracting the drug with a methanol water mixture. The direct and derivative spectrophotometric methods are simple and reliable; the derivative method gives better recovery and lessens interference. Both methods show linearity in the 5-30 microg ml(-1) range of the fluoxetine concentration range. Both HPLC methods (spectrophotometric and spectrofluorimetric detection) use a tetramethylammonium perchlorate buffer-acetonitrile mixture as the mobile phase and a C8 reversed phase column. The UV detection is performed at 226 nm, while the fluorimetric detection is performed by exciting at 230 nm and revealing the emission at 290 nm. The HPLC method with UV detection is more precise, but the procedure with fluorimetric detection is more sensitive.

Efficacies of dexfenfluramine and fluoxetine in preventing weight gain after smoking cessation.

We tested whether 14 wk of dexfenfluramine (30 mg) or fluoxetine (40 mg) treatment would prevent weight gain after subjects quit smoking. Normal-weight women (n = 144) were randomly assigned to drug or placebo on a double-blind basis for 2 wk before quitting smoking and 12 wk thereafter. The fluoxetine group had more dropouts (28/49, 57.1%) than the dexfenfluramine group (17/47, 36.2%), with an intermediate number of dropouts from the placebo group (21/48, 43.8%). All groups gained weight during treatment, but their amount and pattern of weight gain differed. In the first month after quitting smoking, the placebo group gained more weight than either the dexfenfluramine or fluoxetine group (P < 0.05). By 2 mo postcessation, dexfenfluramine still suppressed weight gain in comparison with placebo (P < 0.05); weight gain with fluoxetine was not differentiable from either dexfenfluramine or placebo. By 3 mo postcessation, the dexfenfluramine group had gained 1.0 +/- 0.7 kg, significantly less than either the placebo (3.5 +/- 0.7 kg) or fluoxetine (2.7 +/- 0.5 kg) groups. Three months after drug discontinuation, formerly medicated, but not placebo patients, showed additional weight gain, eliminating differences between groups. Results indicate that weight gain, an adverse accompaniment of smoking cessation, can be minimized to some degree by serotoninergic drugs, although only for the duration of drug treatment.

Development of new treatments for depression.

The mixed actions of the older tricyclic antidepressants make them generally unsuitable as pharmacologic tools in investigating mechanisms of antidepressant effect. Tricyclics are also relatively dangerous in overdose, and their patient acceptability is limited by marked side effects and cardiotoxicity. The current trend in the development of new antidepressants is to identify pharmacologically active molecules that have selective action. Compounds with a selective effect in blocking serotonin reuptake have recently been developed. Among these, fluoxetine is of substantial theoretical interest because, unlike other serotonin uptake inhibitors, it is rather specific and does not appear to down-regulate beta-receptors. Assessment of the relative efficacy of such compounds should provide insight into the mechanisms of antidepressant effect. Prerequisites of clinical trials for new antidepressants are briefly reviewed.