Pharmaceutical Science Concepts

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Questions and Answers

What happens when a solution reaches saturation in solubility equilibrium?

The solute begins to precipitate.

The temperature must be increased.

It continues to dissolve more solute.

No more solid can dissolve. (correct)

In the solubility equation, what does 'γ' represent?

The gas constant.

The radius of the small particles.

The molar volume of the solid.

The surface tension of the liquid. (correct)

Using the Henderson–Hasselbalch equation, which of these variables affects the saturation solubility (ST) of the salt form?

Surface tension of the solution.

The concentration of free acid only.

Both the salt's saturation solubility and the hydrogen ion concentration. (correct)

Only the acid dissociation constant (Ka).

If the surface tension of a powder is 125 dynes/cm and the desired increase in solubility is 5%, what will the size of the particles be?

0.092 µm Signup and view all the answers

What does 'ST' represent in the equation ST = Sa[1 + (Ka/H+)]?

The saturation solubility of the salt form. Signup and view all the answers

How is the solubility of small particles (S) related to large particles (S0) and their respective sizes?

The solubility of small particles is influenced by their radius, surface tension, and molar volume. Signup and view all the answers

Given the molar weight of the salt form is 285 and the free acid is 263, which plays a role in calculating saturation solubility?

Both the salt and free acid's molecular weights are relevant. Signup and view all the answers

What unit is commonly used to express the solubility of an acid form in solution?

milligrams per milliliter (mg/mL) Signup and view all the answers

What is the primary reason that fine materials are more susceptible to environmental factors than coarse materials?

Fine materials have a larger surface area. Signup and view all the answers

How does polymorphism affect the properties of a solid chemical compound?

It changes the stability and solubility of the compound. Signup and view all the answers

Which of the following methods is NOT used to detect polymorphism in compounds?

Ultraviolet-Visible Spectroscopy Signup and view all the answers

Which polymorphic form of cocoa butter has the lowest melting range?

γ form Signup and view all the answers

For a drug to be therapeutically effective, which statement is true regarding its solubility?

It must possess some degree of aqueous solubility. Signup and view all the answers

What occurs when a drug's solubility is inadequate for effective absorption?

It can result in erratic or incomplete absorption. Signup and view all the answers

Which of the following techniques is typically used to determine the degree of solubility of a drug?

Equilibrium solubility method Signup and view all the answers

What chemical modification is commonly used to enhance the solubility of a drug?

Formation of a salt or ester Signup and view all the answers

What is the significance of the eutectic point in a phase diagram?

It represents a minimum melting point in a two-component mixture. Signup and view all the answers

Which of the following properties can be affected by the particle size of drug substances?

Bioavailability and dissolution rate. Signup and view all the answers

What effect does reducing the particle size of poorly soluble drugs have on their bioavailability?

It can enhance their bioavailability when finely subdivided. Signup and view all the answers

Which two products have significantly different oral availability due to particle size variation?

Griseofulvin ultramicrosize and griseofulvin microsize. Signup and view all the answers

What is the main advantage of using ultramicronized formulations?

Enhanced absorption and bioavailability. Signup and view all the answers

What role does particle size play in the dissolution rates of drug substances?

Smaller particles typically have higher dissolution rates. Signup and view all the answers

In the context of preformulation, how does particle size reduction influence stability?

It tends to increase the exposure to moisture. Signup and view all the answers

Which of the following statements is true regarding the relationship between particle size and flow properties?

Smaller particles can lead to poor flow and increased sedimentation. Signup and view all the answers

Which vitamin is commercially available in liquid capsule form?

Vitamin A Signup and view all the answers

What is the primary function of amyl nitrite?

Vasodilation Signup and view all the answers

What property does color intensity of a drug relate to?

Conjugated unsaturation Signup and view all the answers

Which process is used to suppress the taste of a drug considered to be unpalatable?

Using flavors and excipients Signup and view all the answers

What type of formulation can scopolamine hydrobromide be easily pressed into?

Tablets Signup and view all the answers

Which of the following does NOT affect the flavor of a preparation or food product?

Color of the product Signup and view all the answers

What kind of chemical form is propylhexedrine classified as?

Solid ester Signup and view all the answers

In terms of drug formulation, what is an important physical description to consider?

Color and taste Signup and view all the answers

What factor primarily controls the overall absorption of a drug substance?

The dissolution rate of the drug Signup and view all the answers

In the context of drug dissolution, what does the variable 'h' represent in the Noyes-Whitney equation?

The thickness of the boundary layer Signup and view all the answers

Which of the following best explains the purpose of using a highly water-soluble salt of a drug?

To enhance the dissolution rate of the drug Signup and view all the answers

According to the Diffusion layer model, what primarily affects the rate of drug dissolution?

The migration through the boundary layer Signup and view all the answers

What is the significance of the term '∆C' in the equation dC/dt = K ∆C?

It represents the concentration difference at the solid and bulk solutions Signup and view all the answers

What characteristic is NOT a benefit of using fine particles in solid drug forms?

Reduced rate of erosion in the gastrointestinal tract Signup and view all the answers

Which of the following statements is true regarding weak acid salts in an acidic solution?

They precipitate as the free acid in bulk phase Signup and view all the answers

What does the variable 'D' in the Noyes-Whitney equation signify?

The diffusion coefficient of the solute Signup and view all the answers

Study Notes

Preformulation

Preformulation focuses on the physical and chemical properties of a drug substance that are important for its development into a safe and effective dosage form.
A phase diagram can be used to illustrate the different phases of a two-component mixture and identify the eutectic point, where the minimum melting point occurs.

Particle Size

Particle size can affect solubility, bioavailability, stability, flow, and dissolution rate.
Smaller particles have a larger surface area, which can increase solubility and dissolution rate, improving bioavailability.
Examples of drugs affected by particle size reduction include griseofulvin, nitrofurantoin, spironolactone, and procaine penicillin.

Polymorphism

Polymorphism is the existence of a solid chemical compound in more than one crystalline form.
Different polymorphs have different physical and chemical properties, including solubility and stability.
Polymorphs can be characterized using techniques like DSC, hot stage microscopy, X-ray diffraction, and infrared spectroscopy.

Solubility

A drug must have some aqueous solubility for therapeutic efficacy.
Solubility can be improved by converting the drug into a salt or ester form.
Solubility is influenced by particle size, with smaller particles having higher solubility.
The Noyes–Whitney equation describes the rate of drug dissolution from a tablet, taking into account the diffusion coefficient, surface area, and boundary layer thickness.

Dissolution Mechanism

The rate of dissolution is determined by the slowest step in the process, which can be migration through the boundary layer.
The diffusion layer model states that the rate of dissolution is proportional to the concentration difference between the solid surface and the bulk solution.

Organoleptic Properties

Organoleptic properties (color, odor, taste) are important for patient acceptability and can impact the choice of formulation.
The color of a drug substance reflects its chemical structure and level of unsaturation.
Odor can significantly affect the flavor of a preparation.
Unpalatable taste can be masked using flavors, excipients, or coatings.

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Description

Explore the essentials of preformulation, particle size effects, and polymorphism in drug development. Understand how these factors impact solubility, bioavailability, and stability of drug substances. This quiz will enhance your comprehension of critical pharmaceutical principles.