Solutions 1

• What is a solution?

  A mixture forming a single, homogeneous phase

  
• Why should pharmacy students know about solutions?

  Solutions are essential for drug formulation
• What components can be in a solution?

  Solid, liquid, and gas combinations
• What is a solute in pharmacy?

  A solid or liquid dissolved in a solvent

  
• What is the most widely used solvent in pharmacy?

  Water
• What are cosolvents used in aqueous solutions?

  Ethanol, glycerol, propylene glycol
• What are examples of non-aqueous solutions?

  Fixed oils and alcohols
• What types of solutions are used for local applications?

  Lotions, liniments, and mouthwashes
• What are systemic uses of solutions?

  Oral and parenteral solutions
• What are the advantages of solutions in pharmacy?

  • Easier to swallow than solids
  • Rapid absorption
  • Faster onset of action
  • Homogeneous dosage
  • Attractive appearance
• What are the disadvantages of solutions in pharmacy?

  • Bulky to transport
  • Dosage depends on patient ability
  • Possible microbial contamination
  • May require taste-masking
  • Less stable than solids
• What is dissolution?

  Transfer of molecules from solid to solution
• What is solubility?

  Maximum amount of solute that dissolves
• What is the difference between dissolution and solubility?

  Dissolution is a process; solubility is an amount
• What happens during the dissolution process?

  Solute molecules are removed and inserted into solvent
• What forces are involved in the dissolution process?

  Cohesive and adhesive forces
• What does a positive heat of mixing (ΔH) indicate?

  Endothermic reaction that absorbs heat
• What does a negative heat of mixing (ΔH) indicate?

  Exothermic reaction that releases heat
• What is the significance of the Noyes-Whitney equation?

  Describes rate of dissolution of solids
• What do sink conditions refer to in dissolution?

  Absorption faster than dissolution

  
• What happens when concentration (C) exceeds 10% of Cs?

  Non-sink conditions occur
• What is the effect of increasing viscosity on dissolution rate?

  May decrease the dissolution rate
• How does particle size affect dissolution rate?

  Smaller particles increase the dissolution rate
• What is the effect of agitation on dissolution rate?

  Increases the dissolution rate
• What happens to the dissolution rate as concentration (C) increases?

  The dissolution rate decreases
• What are the key variables affecting the Noyes-Whitney equation?

  • Diffusion coefficient (D)
  • Surface area (A)
  • Thickness of diffusion layer (h)
  • Concentration of solute (Cs and C)
• What is the relationship between Cs and C in dissolution?

  Cs is the saturation concentration
• What occurs when C equals Cs?

  The solution is saturated with solute
• What is the significance of boundary layers in dissolution?

  They slow diffusion of solute into solution
• What is the rate-determining step in dissolution?

  Diffusion of solute across boundary layers
• Why is dissolution important for drug absorption?

  Drugs must be in solution to be absorbed

  
• What challenges do drugs with low aqueous solubility present?

  Formulation and bioavailability challenges
• What does the term "rate of solute transfer" refer to?

  Rate of dissolution controlled by diffusion
• What is the effect of temperature on dissolution rate?

  Higher temperatures generally increase the rate
• How does the presence of other ions affect dissolution?

  It can alter the dissolution rate
• What is the role of complexation in dissolution?

  It can enhance or inhibit dissolution
• What is the effect of volume on dissolution rate?

  Increased volume can decrease concentration
• What happens to the dissolution rate as time progresses?

  Rate decreases as concentration increases
• What is the relationship between dissolution and drug formulation?

  Dissolution is crucial for effective drug delivery

  
• What is the significance of the concentration gradient in dissolution?

  It drives the rate of solute transfer