Solutions Flashcards
What are some advantages of the solution dosage form
- Provide homogenous doses
- Doses are easily adjusted
- Immediately available for absorption
- Can be used by any route of administration
- Can be used for patients unable to swallow
What are some disadvantages of the solution dosage form
- Lower stability
- Drug may be insoluble in required solvent
- Microorganism growth - requires preservatives
- Problems with handling, transport, storage
- Requirement of additives (to mask taste)
- Less accurate dosing
Explain the concept of solubility of gases in liquid
Henry’s Law:
- At constant temp, the solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid
Differentiate between dissolution and dissolution rate
Dissolution: transfer of molecules from solid state to solution
Dissolution rate: How fast this process occurs
What are the 2 stages of the dissolution process
- Interfacial reaction: Transfer of solute from solid to liquid (melting)
- Migration of solute from surface of solute through the boundary (stagnant layer) into the bulk solution (rate-limiting step)
What are 2 ways to enhance solubility using the Noyes Whitney equation
- Increase surface area by decreasing particle size
- Reduce diffusion layer thickness (reduces drug concentration in diffusion layer) by mechanical stirring
What is the purpose of in vitro dissolution testing
- to assess the quality of solid drug products
- As a prognostic tool for the performance of solid drug products in the gastrointestinal tract
(main goal is to measure the rate at which the drug releases from the dosage form to the intestine)
What is the partition coefficient equation
organic phase/aqueous phase
Can purified water be used in parenteral solutions
no
What are the conditions for water for injection and what is it used for
-must be pyrogen free
- Does not need to be sterile
used for parenteral solutions
What are advantages of alcohol as a solvent (2)
- higher solubility of many organic solutes
- increased stability (decrease in hydrolysis, decrease in bacterial growth)
List the 7 factors affecting solubility
- Temperature
- Structure of drug
- Solvents
- Solubilizing agents
- Complex formation
- Other solutes
- pH
What is the delta H usually in dissolution processes? How does it affect solubility
usually ENDOthermic, increase in temp. results INCREASE in solubility
If exothermic, increase in temp results DECREASE in solubility
Define salting-in and salting out
Salting- in: adding salt INCREASES solubility
Salting-out: adding salt DECREASES solubility
What is the common ion effect
Adding salt that contains an ion the same as the electrolyte will decrease the solubility of the electrolyte
How does complex formation increase the solubility of a compound
The addition of an electrolyte that reacts with a solute to form an inorganic complex ion can
increase or decrease the solubility of a compound depending upon the solubility of the complex ion that is formed.
What is the purpose of a solubilizing agent?
Describe the 2 classes
Surfactants (form micelles to dissolve hydrophobic drugs)
- are amphiphilic compounds that aggregate into micelles which shield the hydrophobic groups from water contact and provide a hydrophobic phase that hydrophobic drugs can be solubilized in
Complexing agents
- Form a complex with drug to increase solubility (either through stacking interactions or inclusion complex)
What is the MAIN difference between elixir and syrup
Elixir: hydroalcoholic solution
- MUST contain alcohol
Syrup: no alcohol necessary
What are aromatic waters and spirits generally used for?
They are hydrolacooholics (water and alcohol) and are used as flavouring agents
What are common things added to collodion (topical)
Nitrated cellulose or pyroxylin which forms the tough flexible film layer on the skin
What are some substances contained in evacuation enemas
Sodium chloride
Sodium bicarbonate
Sodium phosphates
What are the chemical types associated with Sweet, Sour, Bitter, and Salty tastes?
Sweet: low molecular weight compounds (sucrose, sorbitol, mannitol)
Sour: a result of a lot of H+ ions (acidity)
Bitter: occurs when an ion in a salt has a high molecular weight or the compound is a base (caffeine, codeine)
Salty: ionic compounds (NaCl, Na salicylate)
Contrast between an antioxidant and a chelating agent
Antioxidant:
- disrupts the free radical chain by reacting with free radicals.
- Common: Sodium thiosulfate, sodium bisulfite (sulfur salts)
Chelating agent:
- complexes trace metal ion contaminants in solutions by eliminating their ability to cause the free radical reactions
- Common: EDTA
What are the main classes of preservatives?
Alcohols: ethanol, propylene glycol
Acids: benzoic acid, sodium benzoate
Esters: Paraben - esters of p-hydroxybenzoic acid
