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Review Article
Year : 2018   |  Volume : 6  |  Issue : 2  |  Page : 17-20

Permeability assessment of drug substances using in vitro and ex vivo screening techniques

Solubility and permeability are two important parameters used for the evaluation of drug substance to assess its bioavailability. Although dissolution can be studied using official dissolution apparatus, there are no official techniques to check permeability of drug substances. Apparent permeability index (Papp) is the index used to assess the degree of permeability of drug substances. Papp of any drug substance can be calculated using in vitro, ex vivo, in situ, and in vivo techniques. Parallel artificial membrane permeability assessment and human epithelial colorectal adenocarcinoma cells (Caco-2) are two in vitro models used for high throughput screening and ranking drugs permeability. Ex vivo studies include isolated tissue models and averted intestinal sacs where in situ model includes a segment of the intestine, cannulated, and filled with a probe solution. Ussing chamber study is ex vivo study used to investigate permeability and metabolism where alternative methods such as Caco-2 or intestinal microsomes are useful to study either permeability or metabolism, but not both. In vivo models range from animal gavage in rats to oral dosing to humans in clinical trials. Selection of proper choice depends on degree of screening we are interested in.
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