Introdction To Dissoution And Solubility

Question 1

Question: In what state do drugs have to be when being absorbed?

Answer 1

Answer: They have to be in solution.

Question 2

Question: What is a solution?

Answer 2

A mixture of two or more components that form a single, molecularly homogeneous phase.

Question 3

Question: What is dissolution?

Answer 3

Answer: Dissolution is the process by which a solid dissolves in a solvent to produce a solution.

Question 4

Question: How do drugs generally cross the intestinal wall for absorption into the systemic circulation?

Answer 4

Answer: Generally only drugs in solution can cross the intestinal wall and absorbed into the systemic circulation.

Question 5

Question: How is the solubility of a substance defined?

Answer 5

Answer: The solubility of a substance is defined as the amount that goes into a solution when equilibrium is established between the solute in solution and the excess (undissolved) substance.

Question 6

Question: How is the rate of dissolution of a drug calculated?

Answer 6

Answer: It is calculated using the Noyes - Whitney Equation:

Question 7

Question: What are the factors that affect dissolution rate of solids in liquids?

Answer 7

Question 8

Question: What effect does reducing particle size have on dissolution rate?

Answer 8

Answer: Reducing particle size increases dissolution rate.

Question 9

Question: How does a decrease in porosity impact dissolution rate?

Answer 9

Answer: Decreasing porosity decreases dissolution rate because there is less available surface area for the solvent to interact with the solid.

Question 10

Question: Explain the relationship between increased solubility of a drug and dissolution rate.

Answer 10

Answer: Increased solubility of a drug leads to an increased dissolution rate.

Question 11

Question: What happens to the dissolution rate when the total volume available for dissolution is increased?

Answer 11

Answer: Increased total volume available for dissolution results in an increased dissolution rate.

Question 12

Question: How does a decreased diffusion coefficient affect dissolution rate?

Answer 12

Answer: Decreased diffusion coefficient leads to a decreased dissolution rate.

Question 13

Question: What is the impact of decreased mixing on dissolution rate?

Answer 13

Answer: Decreased mixing decreases dissolution rate.

Question 14

Question: What are the physiological factors affecting drug dissolution?

Answer 14

Question 15

Question: According to the Noyes-Whitney equation, what limits the rate of dissolution from the gastrointestinal tract and other sites?

Answer 15

Answer: The rate of dissolution is limited by the rate of dissolution, as per the Noyes-Whitney equation.

Question 16

Question: Name two key factors highlighted by the Noyes-Whitney equation that influence the rate of dissolution.

Answer 16

Answer: The two key factors are particle size and drug solubility.