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9 Cards in this Set
- Front
- Back
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1. Define & understand partition law & coefficient and application of partition coefficient in pharmaceutical sciences.
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a. Partition Law states that the partition coefficient is constant for given liquids.
i. “If a compound (solid/liquid) is added to a mixture of 2 immiscible liquids, it will distribute itself between 2 layers in a definite concentration ratio.” b. Partition coefficient – ratio of the solubility of the drug in oil to its solubility in water at equilibrium. K = Cu/CL |
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2. Define and understand diffusion, its application & importance of diffusion in the drug absorption.
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a. Diffusion – process of mass transfer of individual drug molecules brought about by random motion associated with a concentration gradient.
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b. Fick’s First Law of Diffusion (Flux eqn)
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J = - D (dc/dx)
D=diff coeff of penetrant Affected by: temp, press, solv props, diffusant |
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3. Understand the importance of the dissolution in the absorption of drugs.
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drug needs to be dissolved a.
Dissolution Process – performed in vitro to determine i. Drug’s properties in the body system ii. Absorption process iii. Amount of drug available for therapeutic action before it can be absorbed via membrane diff. |
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4. What are various types of dissolution apparatus recognized by the USP?
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a. Apparatus 1 & 2:
i. Differ in stirring mechanism basket (app 1) and paddle (app 2) |
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5. Define and describe biopharmaceutics.
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a. Biopharmaceutics – the interrelationship of physicochemical properties of the drug, dosage forms in which the drug is administered, and the route of administration on the rate and extent of systemic drug absorption.
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ii. Physical factors affecting oral absorption:
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1. Membrane physiology:
a. Structure of biological membranes b. Various transport processes 2. Gastro-Intestinal-Tract physiology: a. Characteristics of GIT b. Gastric motility and emptying c. Effect of food d. Other factors: intestinal motility & residence time |
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iii. Physical-Chemical factors affecting oral absorption:
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1. pH partition theory
a. pKa of drug and pH of GIT b. ionized (hydrophilic) to unionized (lipophilic) 2. Dissolution Theory a. Fick’s first law b. Factors affecting Fick’s law |
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What is dissolution theory?
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Drug Absorption from a solid oral dosage depends on the release of the drug substance from the drug product (dissolution), the solubility, and the permeability across the gastrointestinal tract.
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