Drug Dissolution Processes

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Questions and Answers

Which technique is specifically designed for testing the dissolution of low solubility drugs?

Beaker method

Flow-through-cell method (correct)

Rotating basket method

Paddle method

What is a common technique that utilizes a rotating motion to facilitate drug dissolution?

Rotating basket method (correct)

Beaker method

Flask stirrer method

Paddle method

Which of the following methods can be used in a beaker for dissolution testing?

Flow-through-cell method

Rotating basket method

Paddle method

Flask stirrer method (correct)

In dissolution testing, what condition is required to ensure effective measurement?

Sink conditions Signup and view all the answers

Which method is NOT a standard technique for performing drug dissolution testing?

Tap method Signup and view all the answers

What does the dissolution process involve?

A solid drug substance becoming dissolved in a solvent. Signup and view all the answers

Which of the following statements about melting point is true?

Heat of fusion is the amount of heat absorbed or released during melting. Signup and view all the answers

What is the primary importance of drug dissolution in pharmacology?

It facilitates the absorption of drugs into the body fluids. Signup and view all the answers

In the context of the Noyes-Whitney equation, what does 'dC/dt' represent?

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

Which factor does NOT affect the dissolution rate of a drug?

Color of the drug. Signup and view all the answers

What would likely happen to the dissolution rate if the viscosity of the solution increases?

The dissolution rate would decrease. Signup and view all the answers

Which of the following components is part of the Noyes-Whitney equation?

Dissolution rate constant. Signup and view all the answers

Which term best describes the mass of a solute that dissolves in a specific mass of solvent?

Solubility Signup and view all the answers

What type of process can accompany the dissolution of a solid in a solvent?

An exothermic process. Signup and view all the answers

What effect does increasing the surface area of a drug particle have on its dissolution rate?

It increases the dissolution rate. Signup and view all the answers

Study Notes

Preformulation- Dissolution

This topic concerns the dissolution of drugs.
Drug dissolution is vital for the absorption of most drugs.
Drugs in capsules and tablets need to dissolve in gastrointestinal fluids.
Dissolution is a dynamic process, unlike solubility which is static.
Drug dissolution can be measured using techniques like beaker method, flask stirrer method, rotating basket method, paddle method, and flow-through-cell.
Factors affecting drug dissolution include agitation, viscosity, particle size, wettability, porosity, crystalline form, saturation solubility, volume of solution, and excipients.

Drug Dissolution

Matter exists as solid, liquid, and gas.
Melting changes a solid to a liquid using heat.
Solubility is the mass of solute dissolving in a specific mass or volume of solvent at a given temperature.
Dissolution is the process where a solid drug substance becomes dissolved in a solvent.

Melting

Melting point (m.p.) is the temperature at which a solid transforms into a liquid.
Melting necessitates heat.
Heat of fusion (ΔH) is the heat absorbed or released when a system changes its thermodynamic state.
Aspirin has a melting point of 135°C and a heat of fusion of 45.52 cal/g.
Palmitic acid has a melting point of 63°C and a heat of fusion of 39.18 cal/g.

Importance of Drug Dissolution

Most drugs need to dissolve in bodily fluids before absorption.
Drugs in solid dosage forms (like capsules and tablets) must undergo dissolution in the gastrointestinal tract.

Dissolution Process

During dissolution, the starting solid drug disintegrates and deaggregates into individual drug particles.
ΔH (enthalpy change) accompanies solid dissolution in a solvent. ΔH = ΔH₁ + ΔH₂ + ΔH₃ where ΔH₁ is the separation of solute particles, ΔH₂ is the separation of solvent particles, and ΔH₃ is the interaction between the solute and solvent.
Dissolution involves steps on the molecular level, including separating solute, separating solvent, and solute-solvent interaction.
Exothermic process: -2U_sL > U_ss+U_Ll
Endothermic process: -2U_sL < U_ss+U_Ll

Dissolution Methods, Noyes-Whitney Equation, and Dissolution Testing

Drug dissolution rate is often described using the Noyes-Whitney equation: dC/dt = k • A(CS - CB) where
dC/dt = rate of drug dissolution
k = dissolution rate constant (D/h)
A = surface area
CS = saturation solubility of the drug
CB = concentration of the drug in the bulk solution
D = diffusion coefficient
h = thickness of diffusion layer.
Different methods (beaker, flask stirrer, rotating basket, paddle, flow-through-cell) are used for dissolution testing.

Sink Conditions

Sink conditions refer to situations where CB (concentration of drug in the bulk solution) is significantly much smaller than CS (saturation solubility of the drug in the dissolution medium).
Non-sink conditions involve a drug concentration near or exceeding its saturation solubility.

Factors Affecting Drug Dissolution

Factors like particle size, agitation, viscosity, and excipients influence drug dissolution rates.

Polymorphism

Polymorphism can impact drug solubility.
Metastable polymorphs demonstrate faster dissolution rates compared with stable polymorphs.

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Description

This quiz explores the fundamental concepts of drug dissolution and its significance in pharmacology. Covering the dynamic nature of dissolution and various methods for measurement, this quiz will help reinforce critical knowledge related to how drugs dissolve and factors influencing this process. Ideal for students studying pharmacology and drug formulation.