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The effect of chemical modification on the solution structure of derivatives of Substance P: nuclear magnetic resonance study of substituted and retro-inverso analogues
No full textIs generic rifaximin still a poorly absorbed antibiotic? A comparison of branded and generic formulations in healthy volunteers
No full textRifaximin is an antibiotic, locally acting in the gastrointestinal tract, which may exist in different crystal as well as amorphous forms. The branded rifaximin formulation contains the polymorph rifaximin-α, whose systemic bioavailability is very limited. This study was performed to compare the pharmacokinetics of this formulation with that of a generic product, whose composition in terms of solid state forms of the active pharmaceutical ingredient was found to be different. Two tablets (2×200mg) of branded and generic formulations were given to 24 healthy volunteers of either sex, according to a single-blind, randomized, two-treatment, single-dose, two-period, cross-over design. Plasma and urinary samples were collected at preset times (for 24h or 48h, respectively) after dosing, and assayed for rifaximin concentrations by high-performance liquid chromatography-mass spectrometry. Rifaximin plasma and urine concentration-time profiles showed relevant differences when generic and branded rifaximin were compared. Most pharmacokinetic parameters were significantly higher after administration of generic rifaximin than after rifaximin-α. In particular, the differences for Cmax, AUC and cumulative urinary excretion between the generic formulation and the branded product ranged from 165% to 345%. The few adverse events recorded were not serious and not related to study medications. The results of the present investigation demonstrate different systemic bioavailability of generic and branded formulations of rifaximin. As a consequence, the therapeutic results obtained with rifaximin-α should not be translated sic et simpliciter to the generic formulations of rifaximin, which do not claim containing only rifaximin-α and will display significantly higher systemic absorption in both health and disease
Impact of crystal polymorphism on the systemic bioavailability of rifaximin, an antibiotic acting locally in the gastrointestinal tract, in healthy volunteers.
Full text linkBACKGROUND: Rifaximin is an antibiotic, acting locally in the gastrointestinal
tract, which may exist in different crystal as well as amorphous forms. The current marketed rifaximin formulation contains polymorph alpha, the systemic bioavailability of which is very limited. This study compared the pharmacokinetics of this formulation with those of the amorphous form.
METHODS: Amorphous rifaximin was specifically prepared for the study and formulated as the marketed product. Two doses (200 mg and 400 mg) of both formulations were given to two groups of 12 healthy volunteers of either sex according to a single-blind, randomized, two-treatment, single-dose, two-period, cross-over design. Plasma and urine samples were collected at preset times (for 24 hours or 48 hours, respectively) after dosing, and assayed for rifaximin concentrations by high-performance liquid chromatography-mass spectrometry.
RESULTS: For both dose levels, peak plasma concentration, area under the concentration-time curve, and cumulative urinary excretion were significantly higher after administration of amorphous rifaximin than rifaximin-α. Ninety percent confidence intervals for peak plasma concentration, area under the concentration-time curve, and urinary excretion ratios were largely outside the upper limit of the accepted (0.80-1.25) range, indicating higher systemic bioavailability of the amorphous rifaximin. The few adverse events recorded were not serious and not related to the study medications.
CONCLUSION: Rifaximin-α, a crystal polymorph, does differ from the amorphous form, the latter being systemically more bioavailable. In this regard, care must be taken when using - as a medicinal product - a formulation containing even small amounts of amorphous form, which may alter the peculiar pharmacologic properties of this poorly absorbed antibiotic
RIFAMYCIN DERIVATIVES
No full textDisclosed are compounds including rifamycin derivatives having antibacterial activities, wherein the compounds have the following general formula (I) wherein: R is hydrogen or acetyl R1 and R2 are independently selected from the group consisting of hydrogen, ( C1-4) alkyl, benzyloxy, mono- and di-(C1-3) alkylamino-(C1-4)alkyl, (C1-3)alkoxy, (C1-4) alkyl, hydroxy-methyl, hydroxy-(C2-4)-alkyl, and nitro or R1 and R2 taken together with two consecutive carbon atoms of the pyridine nucleus form a benzene ring optionally substituted by one or two methyl or ethyl groups and R3 is hydroxyalkyl (C1-4). In addition, processes to obtain these compounds are described. The compounds have antibacterial activity
Analysis of leukocyte interferon alpha by two-dimensional electrophoresis and immunoblotting
No full textPHARMACEUTICAL COMPOSITIONS COMPRISING POLYMORPHIC FORMS ALPHA, BETA, AND GAMMA OF RIFAXIMIN
No full textPROCESSES FOR THE PRODUCTION OF POLYMORPHIC FORMS OF RIFAXIMIN
No full textCrystalline polymorphous forms of rifaximin (INN) antibiotic named rifaximin alpha and rifaximin beta, and a poorly crystalline form named rifaximin gamma, useful in the production of medicinal preparations containing rifaximin for oral and topical use and obtained by means of a crystallization carried out by hot-dissolving the raw rifaximin in ethyl alcohol and by causing the crystallization of the product by addition of water at a determinate temperature and for a determinate period of time, followed by a drying carried out under controlled conditions until reaching a settled water content in the end product, are the object of the invention
RIFAXIMIN COMPOSITIONS AND METHOD OF USE
No full textForms of rifaximin (INN) antibiotic, such as the poorly crystalline form named rifaximin gamma are described, along with the production of medicinal preparations containing rifaximin for oral and topical use
N,O bis(alkylsilyl)carbamates: new silylating agents in the preparation of chemically bonded stationary phases
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