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
What is the alcohol used for pharmaceutics?
ethanol
What is useful about using alcohol as a solvent?
for preparing drugs with limited water solubility
what is the alcohol limit for kids under 6 years old? 6-12 years? 12 and over?
under 6: 0.5%
6-12: 5%
over 12: 10%
What is a pro and con about using glycerin as a solvent?
pro: has preservative qualities
con: quite viscous so it’s difficult to work with
What are 4 types of solutions based on dose form?
oral solution
ophthalmic solution
parenteral solution
topical solution
what are typical volumes that are convenient to administer for oral solutions?
drops
5ml (tsp)
15ml (tbsp)
What is an important characteristic of ophthalmic/parenteral solutions?
must be sterile
What are 6 different categories of solutions based on vehicle used?
Elixir Tinctures Aromatic waters Collodions Spirits Syrups
What are elixirs?
Clear, sweetened hydro-alcoholic solutions intended for oral use and are usually flavoured to enhance their palatability
What are some pros and cons of using elixirs?
pros:
alcohol content more effective in maintaining both water-soluble and alcohol-soluble ingredients in solution
flexibility in dosing
con:
less viscous/sweet, bad taste is masked as well
alcohol content may be problematic
How should you store elixirs? why?
Tight light-resistant containers, protected from excessive heat
Because of alcohol and volatile oil content
What is a tincture?
Alcoholic or hydroalcoholic solution which may contain between 15-80% alcohol
Why do tinctures contain a high alcohol content?
Dilution of water usually results in precipitation of the ingredients
What dosage forms can tinctures be used for?
oral use
topical use
What are aromatic waters? what are they used for?
clear aqueous solutions saturated with volatile oils and are used for flavouring or perfuming
What are some examples of aromatic waters?
peppermint water
orange flower water
rose water
dill water
What is a spirit? what are they used for?
Similar to aromatic waters, but contain varying amounts of alcohol and therefore higher concentrations of the volatile substances
used for flavouring agents
What are collodions?
Liquid preparations composed of pyroxylin dissolved in a solvent mixture usually composed of alcohol and diethyl ether
What dosage form are collodions used for? How is this dosage form effective?
topical use
When applied, the solvent rapidly evaporates and leaves a thin film behind which serves to protect the skin and if a med is involved, keep in close contact with the skin
What are syrups? What are they used for?
concentrated aqueous preparations of a sugar or sugar substitute and do not contain medication
used as pleasant tasting vehicles where meds can be added to it
What is the most common sugar used? What are some sugar substitutes that could be used?
sucrose
substitutes: sorbitol, glycerin, propylene glycol
What are some preservatives used to preserve syrups? What does the amount of preservative used depend on?
benzoic acid, sodium benzoate, potassium sorbate, parabens, ethanol
depends on the proportion of water available for growth (free water)
What percent of alcohol preserves free water?
18% alcohol
How do you calculate free water present?
Total volume - (volume occupied by sucrose + volume preserved by the sucrose)
What volume does 1 gram of sucrose occupy?
0.632mL
What volume of water is preserved by 1 gram of sucrose?
0.545mL water
What are some guidelines that must be met when picking a colourant?
Match the flavouring
Be soluble
Non-toxic
Stable for the pH of the final product
What conditions do you prepare a syrup under?
Prepare using heat (only if no volatile or heat-liable ingredients present)
What is an endothermic reaction?
If the heat given off in the hydration process is less than the heat required to break the solute-solute and solvent-solvent bonds
What is an exothermic reaction?
If the heat given off in the hydration process is more than the heat required to break the solute-solute and solvent-solvent bonds
What is the maximum percentage of solids that can be found in purified water?
0.001%
What type of alcohol should never be used for pharmaceutics? Why?
Methanol due to its toxicity
What solvent must never be used to replace propylene glycol and why?
ethylene glycol due to toxicity
What is the max alcohol percentage of elixirs?
30%
What are collodions used for?
delivery of keratolytic medications
What flavours would mask a salty tasting drug?
butterscotch apricot peach vanilla wintergreen mint
What flavours would mask a bitter tasting drug?
cherry
mint
anise
What flavours would mask a sweet tasting drug?
chocolate
vanilla
fruit and berry
what flavours would mask a sour tasting drug?
citrus
raspberry
