Article

Overview of factors affecting oral drug absorption

09/2004; 4:167-176.

ABSTRACT This article provides an overview of variables that can affect drug absorption following oral administration in recent years, including both physicochemical properties of the drug and physiological factors of the body. The oral absorption of a drug is a complex process depending upon these factors and their interactions with each other. Solubility and permeability are considered as the major physicochemical factor that affect the rate and extent of oral drug absorption, moreover other physicochemical properties always show their effects to drug absorption via affecting solubility and permeability. In this regard, the Biopharmaceutics Classification System is proved to be a successful predictive tool for drug development. Oral drug bioavailability can also be markedly influenced by physiological factors, such as gastrointestinal pH, gastric emptying, small intestinal transit time, bile salt, absorption mechanism and so on. Thus by understanding the physicochemical properties of a compound and by recognizing the physiological processe affecting drug absorption, also with the awareness of a drug's BCS characteristics, pharmaceutical scientists can better predict drug absorption and develop formulations that can maximize drug bioavailability.

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    ABSTRACT: PURPOSE: Design of biorelevant test setups mimicking the physiological conditions experienced by drugs after oral administration along the passage through the mouth and the GI tract for the in vitro evaluation of diclofenac exhibiting multiple-peak phenomenon during absorption. METHODS: The biorelevant models simulated successively saliva (SSF, pH 6.2-6.75-7.4, 5 mL, 3 min), gastric (SGF-FaSSGF, pH 1.2-1.6, 50-250 mL, 30 min) and intestinal (FaSSIF, pH 6.8, 250 mL, 60 min) fluids. Applying these models, diclofenac free acid and its sodium/potassium salt were comparatively evaluated for dissolution and further characterized by HPLC, optical morphogranulometry, DSC and PXRD to elucidate peculiar behaviors. RESULTS: Diclofenac salts almost completely dissolved in SSF and showed a transitional dissolution pattern before complete precipitation in SGF/FaSSGF. This peculiar pattern correlated with simultaneous chemical modification and formation of agglomerates. With low dissolution in SSF and almost immediately complete precipitation, these behaviors were not observed with diclofenac free acid. Distinct diclofenac features were strongly determined by pH-modifications after oral administration. CONCLUSIONS: The multiple-peak phenomenon observed after administrating a solution, suspension or dispersible formulation of diclofenac salts are likely caused by drug precipitation and agglomeration in the stomach leading to irregular gastric-emptying. Diclofenac free acid may provide more reliable in vivo features.
    Pharmaceutical Research 03/2013; · 4.74 Impact Factor

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