Pharmaceutical solutions Flashcards
Solution?
a system in which molecules of a solute are dissolved in a solvent vehicle.
Solute?
the substance dissolved within a solution
Solvent?
a substance (generally liquid) capable of dissolving other materials (solutes)
Concentration?
the strength of a solution; the number of molecules of solute dissolved in a solvent
Solubility?
the quantity of a given substance that can dissolve in a given solvent under certain conditions
Dissolution?
the process in which a material enters into a solution to become a solute
Dissolution rate?
the rate at which dissolution proceeds
Saturated solution?
a solution in which the solute is dissolved in the solvent at the limit of its solubility (under certain conditions)
Examples of solution formulations
- Parenteral liquids
- Eye drops
- Mouthwashes/gargles
- Ear drops
- Topical lotions
Parenteral liquids need to be?
- Must be sterile
- Small or large volume injections or infusions
- Large volumes need to be isotonic and pH controlled
Eye drops must be?
• Small volume formulations applied onto eyeball for local
effect
• Need to be sterile, isotonic and pH controlled
Mouthwashes must be?
- non-sterile
* wide pH range acceptable
Potential issues with solution formulations?
- Solubility of the drug
- Vehicle acceptability
- pH
- Sterility (and anti- microbial preservatives)
- Chemical stability (and stability enhancers)
- Tonicity
- Viscosity and density
- Aesthetic considerations
- Reproducibility of dosing
- Patient acceptability
- Ease of use
- Ease of manufacture
- Cost
Importance of solubility and
dissolution to pharmacy?
- Drugs must be in solution to be absorbed into the blood
* Drugs can be given as solutions (IV injections and oral solutions
what is vapour pressure?
It is the pressure of this vapour in an closed system in equilibrium whereby some of the more energetic molecules have enough energy to overcome the intermolecular attractions and escape from the surface to form a vapour