Lecture 4: solutions and emulsions Flashcards
Emulsions
two phase system consisting of at least 2 immiscible liquids
heterogenous
thermodynamically unstable
Lipid phase & Aqueous phase + emulsifier = emulsion
When is an emulsion used?
when two immiscible liquids must be dispersed in the same preparation
External phase
continuous phase
flavoring added to this phase
Internal phase
Dispersed, discontinuous phase
Emulsion usage: topical
most often topical use
-O/W = creams, apply to weeping lesions, drying effect
-W/O = lotions, lubricating effect
Emulsions usage: oral
can mask poor taste
improve absorption of some drugs
Emulsions usage - IV
Used to administer calories
Emulsification
addition of energy through trituration or homogenization, creating small droplets of one liquid phase within another and static charge around those droplets
Emulsification Methods
- English (wet gum)
- Continental (dry gum)
- Bottle (shaking)
- Beaker (heating)
Emulsion complexities
- preservatives –> aqueous phase in the free, unbound, unadorbed, unionized state
- antioxidants –> prevent lipid rancidification
- Flavoring –> external phase (continuous)
Solutions
liquid preps that contain one or more chemical solutes dissolved in a suitable solvent or mixture of mutually miscible solvents
- homogenous
solute
present in smaller amount
may include:
- active drug
- flavoring/coloring
- preservatives
- stabilizers
- buffering salts
Solvent
present in larger amount, liquid
- water
- ethanol
- glycerin
- propylene glycol
- isopropyl alcohol
saturated solution
contains the max amount of solute that the solvent can accommodate
Supersaturated solution
larger amount of solute than the solvent can normally accommodate
typically prepared at a higher temperature
Types of solutions
- aqueous solutions
- non-aqueous solutions
Aqueous solutions
drug dissolved in water
most common form of oral solution
can add any flavorings/preservatives/buffering salts
DI or purified water must be used
Ex: syrups, aromatic waters, mucilage, aqueous acids
nonaqueous solutions
contains solvent other than water
+/- water
most commonly alcohol
ex: elidirs, spirits, tincutres
Cautioned use of nonaqeuous solution in which population?
pediatrics
due to alcohol content
Solution administration routes
nonsterile: oral, topical, otic
Sterile: nassal, inhalations, irrigations, injections
Advnatages of solutions
completely homogenous
drug disperse immediately available for absorption (already dissolved)
Solution disadvantages
drug less stable in solution than dry solid form
not all drugs soluble in accepted pharmaceutical solvents
Units of measure of solutions
- Concentration
- molarity
- percent
- ratio strength
Concentration
mg/mL, g/mL
Percent
%w/v (g/100mL)
%v/w (ml/100g)
mg% = mg/100mL
etc
Ratio Strength
X:Y
X grams of solute for every Y mL solution
Solution compounding
- weigh out active ingredient, transfer to beaker
- dissolve drug in minimal amount of distilled water. swirl to mix until completely dissolved
- quantitatively transfer dissolved drug to a 250 mL graduated cylinder, using repeated washings of syrup
- QS the graduate to 118.3 mL with cherry syrup and mix by pouring between the dispensing container and the graduated cylinder
- transfer solution to a 4 oz dispensing container and cap securely
- label product and dispense w/ appropriate measuring device
1 oz to mL
29.57 mL
1 oz to grams
28.35 g
10% solution contains how many grams of drug?
10g per 100 mL
