38 Questions
What is dissolution?
The process by which molecules of a solid substance form a one-phase, homogeneous, molecular mixture with a solvent
Who modified Wagner's scheme for the dissolution of solid dosage forms?
Carstensen
What is the name of the equation that describes the factors affecting dissolution rate?
Noyes-Whitney equation
What is the purpose of dissolution testing?
To measure the rate of drug release
What is the name of the department where Yussif Saaka teaches?
Department of Pharmaceutics
What is the result of the dissolution process?
Drug in solution
What is the name of the university where Yussif Saaka teaches?
University of Health and Allied Sciences
What is the name of the course where dissolution is taught?
SOPH 331 Pharmaceutical Technology II
What is the first step in Carstensen's scheme of drug dissolution?
Initial mechanical lag
According to Carstensen, what controls the liquid access to the solid surface?
Wetting of the solid dosage form surface
What is the rate-limiting step for absorption through the GI membrane for freely water-soluble drugs?
Passive diffusion of the drug
What is the primary rate-limiting step for the absorption of poorly water-soluble drugs?
Dissolution of the undissolved drug
What is the definition of drug release?
The process by which a drug leaves a drug product and is subjected to absorption, distribution, metabolism and excretion
What type of kinetics is characterized by a constant drug release from a drug delivery device?
Zero-order kinetics
What is the result of wetting of the solid dosage form surface?
Decreased contact angles
What is the primary reason for the importance of wetting in the dissolution process?
It controls the liquid access to the solid surface
What is the primary rate-limiting step for drug absorption in Class 2 drugs?
Dissolution
Which class of drugs is most likely to have significant problems with oral drug delivery?
Class 4
What is the primary condition for granting biowaiver for BCS Class 1 drug products?
The drug product is rapidly dissolving
In which of the following media is dissolution testing for biowaiver performed?
0.1 N HCl or Simulated Gastric Fluid USP without enzymes
What is the definition of a rapidly dissolving drug product for biowaiver?
Not less than 85% of the labeled amount of the drug substance dissolves within 30 minutes
For which class of drugs is the correlation of in-vivo results with dissolution tests most accurate?
Class 2
Under what conditions is permeability the rate-controlling step for drug absorption?
For Class 3 drugs with high solubility and low permeability
What is the primary advantage of IVIVC for Class 1 drugs formulated as extended-release products?
Absorption is controlled by the availability of the drug in the GIT
What type of apparatus is suggested by the USP for chewable tablets, except for ampicillin chewable tablets?
Paddle method
What type of dissolution testing method is commonly used for buccal tablets?
USP apparatus 2
What type of apparatus is frequently used for suspensions?
USP apparatus 2
What is the typical way of testing suppositories?
Placing the suppository in a dialyzing bag made of special membrane or cellophane material
What type of dissolution testing method is used for extended-release dosage forms?
Multipoint dissolution profiles in three other media
What is the suggested duration for the acid stage of dissolution testing for delayed-release dosage forms?
2 hours
What is the pH range of the buffer media used for the buffer stage of dissolution testing for delayed-release dosage forms?
pH 4.5 - 7.5
What is the purpose of using a dialyzing bag made of special membrane or cellophane material for suppositories?
To contain the suppository during dissolution testing
What is the main advantage of using a basket with slots in dissolution testing?
It prevents blockade of the mesh and allows for testing of suppositories with low specific gravity
What is the purpose of the synthetic membrane in the Franz cell system?
To separate the dosage form from the sampling fluid
What is placed in the open donor chamber of the diffusion cell?
Dosage form
What is monitored in the diffusion cell system?
The diffusion of the drug from the topical product
What is the purpose of the receptor fluid in the diffusion cell system?
To collect samples for assaying the drug concentration
What type of dosage forms are typically tested using the Franz cell system?
Topical dosage forms
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
This quiz covers the principles of dissolution, drug-release kinetics, and the Noyes-Whitney equation in pharmaceutical technology. Understand the key concepts and factors affecting dissolution in pharmaceutics.
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