Solutions Flashcards
How can mixtures be divided into two main groups?
Homogenous (uniform composition)
Heterogenous (non-uniform composition)
What is the only type of homogenous mixture?
Solutions (particles are small and evenly dispersed)
What are the types of heterogenous mixtures?
Colloid (particles are medium and dispersed, but do not settle)
Suspension (Particle are large and settle out)
What is the definition of a pharmaceutical solution?
A chemicaly and physically homogenous liquid preparations of two or more substances
What are some excipients added to solutions?
Flavouring, sweeteners, colourants, and preservatives are some examples
What solvents are used in pharmaceutical solutions?
Water is most commonly used and desirable, but other solvents are also used
Alcohol (94-96%)
Glycerin
Propylene glycol
Oils
For topical applications, are polar solvents better compared to non-polar solvents?
No, non-polar solvents are more liklely to absorb into the skin (lipid-based)
What is the utility of solutions as a dosage form?
Injectable drugs
Pediatric formulations
Opthalmic preparations
Some lotions
Sprays
Liquid dosage forms are prefered by children and people who have a hard time swallowing other oral dosage forms
What are the advantages of solutions in pharmacy?
Solutions skip disintegration and dissoultion, therefore the absorb the faster compared to solid dosage forms
Can be intended for multiple routes of administration
Flexible dosing, different volumes can be used depending on the circumstances
No shaking needed (solute is completely disolved into the solvent)
What are some disadvantages of solutions in pharmacy?
Increased sensitivity to environmental conditions
Reduced technical accuracy
Solubilty of drug must match excipients
Bulky storage and transport
What is the difference between solubility and dissolution?
Solubility: The quantity of solute to form a saturated solution (constant at a given temperature)
Dissolution: The transfer of molecules and ions from a solid phase into a solution (describes the process)
How can dissolution be enhanced?
Trituration can reduce particle size and decreases solution time
Heat
Vigourous shaking
What physiochemical factors affect solubility?
Molecular weight and volume
Precense of functional groups and their position (structure)
Acids or bases (pH dependent solubility)
Do aqueous solutions have different boiling and freezing points compared to pure water
Solutes increase boiling point and reduce freezing point
What are the different types of solutions?
Gases in Liquids (effervescent tablets)
Liquids in Liquids (elixirs)
Solids in Liquids (drug powders for injectable reconstitution)
Does pressure increase solubilty of gases in liquids?
Yes
Does temperature increase solubility of gases in liquids?
No, increased temperatures reduce the amount of solvent that can be dissolved into the solvent
What happens to gases in liquids when a different solute is added to the solution?
If the solute has a greater affinity for water than the dissolved gas, the solution will bubble of some gas
What is miscibility?
Expresses the mutual solubility of components in a liquid-liquid system (mixes without separating)
Are all liquids miscible with each other?
No, some are only miscible under certain conditons (proportion and temperature), while others are completely immiscible
How does temperature impact solubility?
With endothermic substances, solubility increases with temperature (disolution requires the input of energy)
With exothermic substances, solubility decreases with increases in temperature (dissolution results in the release of energy)
With Normothermic substances, solubility does not change with temperature (energy is neither absorbed or released during dissolution)
What is polarity?
It is the separation of electric charge leading to a molecule or its chemical groups having an electric dipole moment, with a negatively and positively charged ends
What are some non-polar solvents used in pharmceutical preparations?
Fixed oils (non-volatile): ex. vegetable oils
Hydrocarbons: ex. mineral oils
Non-polar solvents are used as a vehicle for injections and for external preparations (topical)
What is the most desirable polar solvent?
Distilled Water