Relative bioavailability study of two oral formulations of mycophenolate mofetil in healthy volunteers Background: The bioequivalence of different formulations of a same pharmaceutical product must be tested empirically. Aim: To evaluate the relative bioavailability for an oral formulation of mycophenolate mofetil (MMF) (Linfonex TM) compared to the reference formulation (Cellcept TM) to determine the bioequivalence between both formulations. Material and Methods: A randomized, crossover, double-blind trial in 22 healthy male volunteers, who received a single oral dose of 1000 mg of Linfonex and Cellcept with a washout period of 10 days. Plasma levels of the drug were determined by high performance liquid chromatography. Plasma concentrations were plotted and maximum concentration, area under the plasma concentration versus time between 0 and 12 hours after administration and area under plasma concentration curve versus time after administration between 0 and infi nity, were calculated for both products. Results: The active compound, mycophenolic acid, was similarly absorbed in both formulations. No statistically signifi cant differences were found in calculated pharmacokinetic parameters between both formulations. Conclusions: Linfonex TM 500 mg is bioequivalent to Cellcept TM 500 mg.
Tamoxifen (Tmf), is a standard of care for women with estrogen receptor positive (ER+) breast cancer. Endoxifen is a Tmf metabolite generated by cytochrome P450 2D6 (CYP2D6). Antidepressive agents (AD) are often prescribed to women with breast cancer not only for depression, but also for anxiety and hot flashes. Some AD are substrates or inhibitors of the Tmf metabolic pathway. Therefore there may be interactions when Tmf and AD are prescribed simultaneously. Oncologic protection afforded by Tmf may become less effective or null when AD are indicated, especially in poor metabolizing patients. We performed an update of the literature about the criteria for choosing AD in women receiving Tmf. Tricyclic AD, paroxetine and fluoxetine should be avoided in patients receiving Tmf, because they are strong inhibitors of CYP2D6. Bupropion, duloxetine and sertraline are only moderate inhibitors of the cytochrome and are not contraindicated. Citalopram, desvenlafaxine, escitalopram, milnacipran and venlafaxine are recommended, because they do not influence the metabolism and clinical efficacy of Tmf and have fewer drug interactions. However, other additional pharmacological and clinical issues should be considered when choosing an antidepressant in women with breast cancer.
Bioequivalence of two brands of clarithromycin in modified-release tablets available in the Chilean pharmacopeia A comparative bioavailability study was conducted in order to test the bioequivalence between two formulations of clarithromycin 500 mg in tablets of modified release, a local formulation (Pre-Clar UD®), and the original product (Klaricid UD®). A microbiological assay was used to determine the antibiotic plasmatic concentrations. The assay is based on the correlation between the inhibition of bacterial growth in agar plates and the plasmatic concentration of clarithromycin. A total of sixteen non-smokers, healthy young volunteers participated and completed the study protocol which was approved by the local ethic committee. According to the guidelines recommended by the FDA and by means of our findings, we can assure that Pre-Clar UD® and Klaricid UD® are bioequivalents. Therefore, we may assume that both products are interchangeable without compromising clinical efficacy.Key words: Clarithromycin; Pharmacokinetics; Bioequivalence. IntroducciónLa biodisponibilidad de un fármaco es una medida de la cantidad y de la velocidad con que éste llega a la circulación sistémica 1 . Por su parte, la biodisponibilidad relativa o bioequivalencia es una medida comparativa de la calidad de una formulación farmacéutica, en donde se compara un producto nuevo (en términos de la velocidad y de la cantidad de principio activo que entrega) con el producto original (innovador del mercado). Conociendo la calidad de la formulación de un producto farmacéutico, el médico puede disponer de alternativas farmacéuticas, a distintos precios y sin comprometer la eficacia clínica 2 . Por otra parte, la intercambiabilidad es el acto realizado por un médico de utilizar indistintamente una formulación u otra, disponiendo de elementos de juicio suficientes para asegurar que la calidad de uno de los productos farmacéuticos es comparable o similar a la del otro (alternativas farmacéuticas) 3 . El tipo de formulación con mayor variedad y la más utilizada es el comprimido, dada la facilidad de administración de principios activos, así como por la estabilidad de éstos. En este estudio se utilizaron comprimidos de liberación controlada, que proveen la dosis requerida en forma inmediata, seguida de una liberación gradual del fármaco en cantidad suficiente para mantener una respuesta terapéutica por un período de tiempo extendido 1 , siendo este último dependiente de uno o más factores del tracto gastrointestinal.La claritromicina es un antimicrobiano macró-lido, derivado semisintético de la eritromicina. Difiere de ésta solamente en la metilación del
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