Solution Dose Forms Flashcards
What is a solution?
A thermodynamically stable, one-phase system composed of two or more components, one of which is completely dissolved in the other
What is a solute?
a component present in the smaller amount
what is a solvent?
a component present in the larger, liquid amount
What is the most common solvent used?
water
What are typical pharmaceutical solutes?
active drug components
colouring/flavouring agents
preservatives
stabilizers for buffering salts
What are characteristics of an appropriate solvent?
must completely dissolve the drug/other solid ingredients
nontoxic and safe for ingestion/topical application
aesthetically acceptable in terms of appearance, aroma, texture, and/or taste
What are 5 advantages to solution dose forms?
1) completely homogenous doses
2) immediate availability for absorption into the body
3) flexible in terms of dose adjustment
4) may be used by any route of administration
5) can be administered to patients who cannot swallow tablets/capsules
What are 5 disadvantages to solution dose forms?
1) less stable than dry solid form
2) some drugs are not soluble in solvents that are acceptable for pharmaceutical use
3) need to use taste masking for drugs with bad taste
4) heavier and bulkier than solids → more difficult to handle, package, transport, and store
5) they require measurement by the patient or caregiver
What are 3 ways to classify pharmaceutical solutions?
route of administration
solvent
concentration
What are three ways to increase the rate of dissolution?
temperature
stirring
reduction of particle size
What are two conditions that must be met for rate of dissolution to increase with heat?
solvent must be non-volatile
solute stable to heat
When should you filter your solution? When should you never filtrate?
Filter: get rid of small particulates (packaging materials, small amounts of degradation products)
Never filter to remove undissolved solute
What is solubility?
the maximum concentration to which a solution may be prepared with an agent and a solvent
What phenomenon is responsible for the physical state of a substance? Which is the most important?
intermolecular forces
H-bonding
What occurs when a solute dissolves?
intermolecular forces are overcome by forces of attraction between solute and solvent molecules
breaking of solvent-solvent and solute-solute bonds
establishment of solvent-solute bonds
Why does an increase in temperature increase solubility?
solids absorb heat when they are dissolving
they have a positive heat of solution, so there is an increase in solubility with increasing temperature
are volumes of solution components additive? Why or why not?
no
the molecules experience different intermolecular forces than in pure substances
difference in molecule size and shape so the mixed molecules are going to fit together differently than molecules of a pure substance
Does the volume of a solvent increase or decrease when salt is added? What do you do to fix this?
decrease
add precise amount of salt water to a precise amount of water
transfer to a graduated cylinder and qs ad with water to desired volume
What is displacement volume?
the volume occupied by the powder when a suitable diluent is added during reconstitution
What are 3 important generalization about solubility?
Like dissolves like
halogens decrease solubility
monovalent cations have greater water solubility than divalent cations
What does “like dissolve like” mean?
a solvent having a chemical structure similar to the solute will likely dissolve it
ex) similar polar functional groups
why do halogens decrease solubility?
they increase the molecular weight but not the polarity
How do the following parameters of the Noyes-Whitney equation affect the rate of dissolution? D, A, delta(S), cs, c
D = negative A = positive delta(S) = positive cs = positive or negative c = positive
What are 4 typical pharmaceutical solvents?
Purified water
Alcohol
Propylene glycol
glycerin
How do you obtain purified water?
Distillation
Ion exchange
Reverse osmosis