Podcast
Questions and Answers
What is dissolution?
What is dissolution?
- The process of a solid dissolving into a gas
- The process of solid particles becoming smaller
- The process of a solid changing its shape
- The process by which molecules of a solid substance form a one-phase, homogeneous, molecular mixture with a solvent (correct)
Who modified Wagner's scheme for the dissolution of solid dosage forms?
Who modified Wagner's scheme for the dissolution of solid dosage forms?
- Whitney
- Carstensen (correct)
- Noyes
- Saaka
What is the name of the equation that describes the factors affecting dissolution rate?
What is the name of the equation that describes the factors affecting dissolution rate?
- Carstensen's equation
- Saaka's equation
- Wagner's equation
- Noyes-Whitney equation (correct)
What is the purpose of dissolution testing?
What is the purpose of dissolution testing?
What is the name of the department where Yussif Saaka teaches?
What is the name of the department where Yussif Saaka teaches?
What is the result of the dissolution process?
What is the result of the dissolution process?
What is the name of the university where Yussif Saaka teaches?
What is the name of the university where Yussif Saaka teaches?
What is the name of the course where dissolution is taught?
What is the name of the course where dissolution is taught?
What is the first step in Carstensen's scheme of drug dissolution?
What is the first step in Carstensen's scheme of drug dissolution?
According to Carstensen, what controls the liquid access to the solid surface?
According to Carstensen, what controls the liquid access to the solid surface?
What is the rate-limiting step for absorption through the GI membrane for freely water-soluble drugs?
What is the rate-limiting step for absorption through the GI membrane for freely water-soluble drugs?
What is the primary rate-limiting step for the absorption of poorly water-soluble drugs?
What is the primary rate-limiting step for the absorption of poorly water-soluble drugs?
What is the definition of drug release?
What is the definition of drug release?
What type of kinetics is characterized by a constant drug release from a drug delivery device?
What type of kinetics is characterized by a constant drug release from a drug delivery device?
What is the result of wetting of the solid dosage form surface?
What is the result of wetting of the solid dosage form surface?
What is the primary reason for the importance of wetting in the dissolution process?
What is the primary reason for the importance of wetting in the dissolution process?
What is the primary rate-limiting step for drug absorption in Class 2 drugs?
What is the primary rate-limiting step for drug absorption in Class 2 drugs?
Which class of drugs is most likely to have significant problems with oral drug delivery?
Which class of drugs is most likely to have significant problems with oral drug delivery?
What is the primary condition for granting biowaiver for BCS Class 1 drug products?
What is the primary condition for granting biowaiver for BCS Class 1 drug products?
In which of the following media is dissolution testing for biowaiver performed?
In which of the following media is dissolution testing for biowaiver performed?
What is the definition of a rapidly dissolving drug product for biowaiver?
What is the definition of a rapidly dissolving drug product for biowaiver?
For which class of drugs is the correlation of in-vivo results with dissolution tests most accurate?
For which class of drugs is the correlation of in-vivo results with dissolution tests most accurate?
Under what conditions is permeability the rate-controlling step for drug absorption?
Under what conditions is permeability the rate-controlling step for drug absorption?
What is the primary advantage of IVIVC for Class 1 drugs formulated as extended-release products?
What is the primary advantage of IVIVC for Class 1 drugs formulated as extended-release products?
What type of apparatus is suggested by the USP for chewable tablets, except for ampicillin chewable tablets?
What type of apparatus is suggested by the USP for chewable tablets, except for ampicillin chewable tablets?
What type of dissolution testing method is commonly used for buccal tablets?
What type of dissolution testing method is commonly used for buccal tablets?
What type of apparatus is frequently used for suspensions?
What type of apparatus is frequently used for suspensions?
What is the typical way of testing suppositories?
What is the typical way of testing suppositories?
What type of dissolution testing method is used for extended-release dosage forms?
What type of dissolution testing method is used for extended-release dosage forms?
What is the suggested duration for the acid stage of dissolution testing for delayed-release dosage forms?
What is the suggested duration for the acid stage of dissolution testing for delayed-release dosage forms?
What is the pH range of the buffer media used for the buffer stage of dissolution testing for delayed-release dosage forms?
What is the pH range of the buffer media used for the buffer stage of dissolution testing for delayed-release dosage forms?
What is the purpose of using a dialyzing bag made of special membrane or cellophane material for suppositories?
What is the purpose of using a dialyzing bag made of special membrane or cellophane material for suppositories?
What is the main advantage of using a basket with slots in dissolution testing?
What is the main advantage of using a basket with slots in dissolution testing?
What is the purpose of the synthetic membrane in the Franz cell system?
What is the purpose of the synthetic membrane in the Franz cell system?
What is placed in the open donor chamber of the diffusion cell?
What is placed in the open donor chamber of the diffusion cell?
What is monitored in the diffusion cell system?
What is monitored in the diffusion cell system?
What is the purpose of the receptor fluid in the diffusion cell system?
What is the purpose of the receptor fluid in the diffusion cell system?
What type of dosage forms are typically tested using the Franz cell system?
What type of dosage forms are typically tested using the Franz cell system?
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Study Notes
Objectives
- Understand the principles of dissolution
- Understand drug-release kinetics
- Understand the Noyes-Whitney equation
- Understand factors affecting dissolution rate
- Understand dissolution testing
- Understand USP apparatuses and dosage form-specific testing
Introduction to Dissolution
- Dissolution is the process by which molecules of a solid substance form a one-phase, homogeneous, molecular mixture with a solvent
- Wagner's scheme proposes the following processes involved in the dissolution of solid dosage forms:
- Disintegration
- Deaggregation
- Dissolution
- Carstensen's modified scheme includes:
- Initial mechanical lag
- Wetting of the dosage form
- Penetration of the dissolution medium into the dosage form
- Disintegration
- Deaggregation of the dosage form and dislodgement of the granules
- Dissolution and occlusion of some particles of the drug
Dissolution Rate-Limiting Steps
- The rate of drug dissolution can become the only rate-limiting step before it appears in the blood
- When the dosage form is placed into the GIT in solid form, there are two possible rate-limiting steps:
- The solid must first dissolve, and the drug in solution must then pass through the gastrointestinal (GI) membrane
- The rate of absorption of poorly water-soluble drugs will be limited by the rate of dissolution of the undissolved drug or disintegration of dosage form
Drug Release Kinetics
- Zero-order kinetics: constant drug release from a drug delivery device (i.e., amount of drug released per unit of time is constant)
IVIVC (In Vivo/In Vitro Correlation)
- Correlation of in-vivo results with dissolution tests is most accurate for Class 2 drugs
- For Class 1 drugs, good IVIVCs are obtained when the drug is formulated as an extended-release product
- IVIVC is not possible for Class 4 drugs due to significant problems for oral drug delivery
Dissolution of Dosage Forms
- Immediate release, solid oral: biowaiver may be granted for BCS Class 1 drug products for bioequivalence studies, if the drug product is rapidly dissolving
- Powders: dissolution testing can be performed using paddle method or flow-through cell method
- Dosage forms for the oral cavity: sublingual tablets, buccal tablets, and chewable tablets have specific dissolution testing methods
- Suspensions: USP Apparatus 2 is frequently used
- Modified-release: extended-release and delayed-release dosage forms have specific dissolution testing requirements
- Suppositories: typically, the suppository is placed in a dialyzing bag made of special membrane or cellophane material
- Topical dosage forms (creams, ointments, gels): an open chamber diffusion cell system, such as a Franz cell system, is used
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