Drug Dissolution and Factors Affecting Absorption Quiz

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Questions and Answers

What does Fick’s First Law of Diffusion state?

The rate of diffusion is proportionate to concentration gradient, cross-sectional area, and diffusion coefficient (correct)

The rate of diffusion is directly proportionate to concentration gradient and chemical potential

The rate of diffusion is inversely proportionate to concentration gradient and cross-sectional area

The rate of diffusion is proportionate to concentration gradient and temperature

What does the diffusion coefficient (D) measure?

The amount of solute diffusing across 1 cm$^2$ in 1 second (correct)

The amount of solvent diffusing across 1 cm$^2$ in 1 second

The rate of change of solvent concentration with respect to time

The rate of change of solute concentration with respect to distance

What does the term 'J' represent in the context of diffusion?

Chemical potential of the solute

Diffusion coefficient of the solute

Concentration gradient of the solute

Flux, measuring the amount of substance that will flow through a unit area during a unit time interval (correct)

When does diffusion stop according to the provided text?

Diffusion stops when the concentration gradient (dc/dx)* equals 0 Signup and view all the answers

What is the main buffer system in the intestine?

Bicarbonate system Signup and view all the answers

What is the approximate fasting pH range in the duodenum of the small intestine?

6.2-7.0 Signup and view all the answers

What is the fasting concentration of bile salts in the intestinal fluid?

3 mM Signup and view all the answers

What is the fasting surfactant concentration of bile salts compared to the fed state?

Fasting is higher Signup and view all the answers

What is the approximate ratio of bile salt to phospholipids in the intestinal fluid?

4:1 Signup and view all the answers

What is the approximate thickness of the unstirred water layer adjacent to the intestinal membrane?

30-50 µm Signup and view all the answers

How much intestinal surface area is needed for sufficient oral absorption?

800 cm² Signup and view all the answers

What is the in vivo effective permeability (Peff) of the intestine?

$10^{-4}$ cm/s Signup and view all the answers

According to the Biopharmaceutical Classification System (BCS), which class represents substances with high solubility and high permeability?

Class I Signup and view all the answers

What is the transit time of the stomach in the fasting state for drug absorption?

12 minutes Signup and view all the answers

According to FDA guidance, what is the pH range for securing a waiver of in vivo bioavailability and bioequivalence studies for solid oral dosage forms?

1.2-6.8 Signup and view all the answers

What is the deciding factor for drug dissolution in orally administered products?

Solubility Signup and view all the answers

What is the driving force for diffusion?

Frictional force exerted by viscosity of the solution Signup and view all the answers

What is the function of the diffusion coefficient?

It is a function of temperature/viscosity and related to solute radius Signup and view all the answers

What does Fick's 2nd Law of Diffusion explain?

The diffusion process and changes in concentration along the direction of diffusion Signup and view all the answers

What happens when the concentration gradient decreases according to Fick's 2nd Law of Diffusion?

Diffusion slows down Signup and view all the answers

What does Einstein's random walk theory determine?

The diffusion coefficient Signup and view all the answers

How is the diffusion coefficient often experimentally measured?

In a two-chamber vessel separated by a porous membrane Signup and view all the answers

What is the function of a diffusion cell?

To monitor the diffusion of a drug between donor and receptor chambers Signup and view all the answers

What does passive diffusion involve?

Mass transfer of molecules based on a concentration gradient Signup and view all the answers

What does sink conditions imply in diffusion?

Constant removal of drug in the receptor chamber and replacement of solvent Signup and view all the answers

What is the goal of sink conditions in diffusion?

To drive concentration gradient to a constant Signup and view all the answers

What does Fick's 1st Law of Diffusion explain?

Diffusion occurs according to a concentration gradient Signup and view all the answers

What does Fick's 2nd Law of Diffusion predict?

How diffusion will cause a concentration change with respect to time Signup and view all the answers

What is the primary objective of dissolution rate studies?

Assessment of oral drug absorption under physiological conditions Signup and view all the answers

Which factor can influence the dissolution rate of drugs?

Agitation Signup and view all the answers

What is the role of bile salts in drug dissolution?

Enhancing the solubility of lipophilic drugs Signup and view all the answers

Which step is involved in drug dissolution from a solid dosage form?

Swelling Signup and view all the answers

What does the Biopharmaceutical Classification System (BCS) utilize for dissolution studies?

250mL of dissolution fluid Signup and view all the answers

How are dissolution tests carried out?

Under simulated in vivo sink conditions with constant replacement of the dissolution medium Signup and view all the answers

What is the influence of excipients on drug dissolution?

They can increase or decrease the aqueous solubility of drugs Signup and view all the answers

How does particle size affect drug dissolution rate?

Micronization of particles increases the dissolution rate and oral absorption Signup and view all the answers

What is the role of diffusion layer thickness in drug dissolution?

The thickness decreases over time, leading to an increase in the intrinsic dissolution rate Signup and view all the answers

What is the purpose of dissolution testing in drug quality control?

To determine the bioavailability of a drug Signup and view all the answers

What is the significance of in vitro dissolution testing?

It is the most important quality control test for many pharmaceutical preparations Signup and view all the answers

Study Notes

Drug Dissolution and Factors Affecting Dissolution Rate

The process of drug dissolution is a kinetic process of solid particles going into solution, which is vital for determining the bioavailability of a drug in vivo.
In vitro tests are used for drug quality control, with dissolution testing being the most important quality control test for many pharmaceutical preparations.
Drug dissolution from a solid dosage form involves steps such as wetting, penetration of the solvent, swelling, disintegration, and dissolution of individual drug particles.
Dissolution tests are carried out under simulated in vivo sink conditions with constant replacement of the dissolution medium and specific apparatuses and protocols as described by the USP.
The primary objective of dissolution rate studies is the assessment of oral drug absorption under physiological conditions, and the Biopharmaceutical Classification System (BCS) utilizes 250mL of dissolution fluid.
Physiological conditions in the gastrointestinal (GI) tract after ingesting 250mL of water are reported, including stomach and intestinal pH levels.
Factors influencing drug dissolution rate include the diffusion layer thickness, agitation, pH, solubility, and the influence of excipients, surfactants, bile salts, particle size, and solid state properties.
The thickness of the diffusion layer decreases over time, leading to an increase in the intrinsic dissolution rate, and the dissolution rate depends on the way solid particles are scattered over the bottom of the vessels.
The pH of the dissolution medium, the solubility and dissolution of weak electrolytes and salts, and the influence of excipients can affect the dissolution rate of drugs.
Excipients in drug formulations can increase or decrease the aqueous solubility of drugs, with different effects from substances such as lactose, starch, lubricants, and surfactants.
Bile salts can form micelles, enhancing the solubility of lipophilic drugs and potentially increasing the dissolution rate of poorly water-soluble drugs.
Particle size and surface area have a direct relationship with the dissolution rate, with micronization of particles increasing the dissolution rate and oral absorption.

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Description

Test your knowledge of drug dissolution and factors affecting dissolution rate with this quiz. Explore the key steps involved in drug dissolution from solid dosage forms, the importance of in vitro dissolution testing, and the impact of factors such as pH, solubility, particle size, and excipients on drug dissolution rate. Gain insights into the role of bile salts, surfactants, and the Biopharmaceutical Classification System in assessing oral drug absorption.