Oral Solution Dosage Forms - ALL NOTES Flashcards
How can rate of absorption be limited?
-By precipitation when a solution is overly concentrated so will come out of solution
What is a pharmaceutical solution?
-Liquid preparations in which the therapeutic agent and the various exipients are dissolved in the chosen solvent system
What are advantages of pharmaceutical products as solutions?
-Aids young children and people that struggle;e to swallow
-Can be flavoured
-Drug is already dissolved so quicker uptake
What are disadvantages of pharmaceutical products as solutions?
-Not as stable as a tablet
-bulky to store, ship and carry
-Bottle could break
-Not suitable for drugs that are hydrolised or insoluble
What is an example of a co-solvent?
-Ethanol
-Glycerol
What is an example of an antioxidant ?
-Ascorbic acid
What is an example of an antimicrobial preservative ?
-Benzalkonium chloride
What is an example of a pH adjuster?
-citric acid
What is an example of an isotonic adjuster?
-Sodium chloride
-glucose
What is an example of a viscosity enhancer?
-Hydroxmethylcellulose
What is an example of a chelating agent?
-EDTA
What is an example of a natural sweetener?
-Sucrose
What is an example of an artificial sweetener ?
-Aspartame
What kind of water must be used in parenteral solutions?
-Distilled then further purified to remove pyrogens
What kind of water must be used in non-parenteral solutions?
-Distilled
What is high solubility?
-Readily incorporated into the vehicle and formulated as an oral solution
What is moderate solubility?
-Solubility enhanced using co-solvents or related methods
What is low solubility?
-Formulated as an alternative dosage form eg suspension
What physicochemical factors affect solubility of therapeutic agents?
-Molecular weight
-Particle size
-Number of hydrogen bonds
-Hydrophilic groups
-Amorphous properties
What happens if the pH>pKa of an acid drug?
-Solubility of acidic drug increases
What happens if the pH<pKa of a basic drug?
-Solubility of basic drug increases
Aspirin pKa =3.0
pH stomach = 1.2
Will the weak acid more mainly ionised or unionised?
-Unionised
Aspirin pKa =3.0
pH stomach = 6.8
Will the weak acid more mainly ionised or unionised?
-ionised
Chlorpromzine pKa = 5.0
pH stomach = 1.2
will the weak base more mainly ionised and unionised?
-Ionised
Chlorpromzine pKa = 5.0
pH stomach = 6.8
will the weak base more mainly ionised and unionised?
-unionised
What is the acceptable pH range for oral administration?
-5 to 8
How can pH be optimised?
-use of a buffer
How can you convert a weak acid to a salt?
-If you increase the pH in the diffusion layer the dissolution rate and saturation solubility will increase even though the bulk pH is the same
Why can’t some weak acids be converted to salts to increase solubility?
-May be more prone to hydrolysis, chemical stability, manufacturability
How can co-solvents increase solubility?
-Used as well as water to enhance the solubility by allowing more ionisation
How does micellar solubilisation work?
-Incorporates drugs into or onto micelles
What is cyclodextrin complexation?
-Enzymatically modified starches composed of glucopyranose with a hydrophobic cavity, hydrophilic exterior that holds a hydrophobic drug with poor water solubility
What approaches can help drug solubilisation?
-pH
-Co-solvent
-Complexation
-Change to salt
-Disperse phase
-More amorphous
What is a vehicle ?
-Drugs can put themselves in to be transported
What is pourability?
-How well a solution can be poured, relates to viscosity
What is palability?
-How agreeable the taste of a solution is
What are the purposes of excipients ?
-Facilitate administration
-Protect the formulation from issues regarding physical and chemical stability
What are the purposes of buffers?
-Control pH of the formulated product to maintain solubility and enhance stability
What are the purpose of sweetening agents?
-Increase the palatability of the therapeutic agent
What are the purpose of viscosity-enhancing agents?
-Ensure the accurate measurement of the volume to be dispensed
How is viscosity increased?
-The addition of non-ionic or ionic hydrophilic polymers
What is the purpose antioxidants ?
-Enhance the stability of therapeutic agents that are susceptible to chemical degradation by oxidation
What are chelating agents?
-Form complexes with heavy metal ions involved in oxidative degradation of therapeutic agents
What do preservatives do?
-Control the microbial bioburden of the formation
What are the ideal properties of preservative?
-Broad antimicrobial spectrum
-chemically and physically stable over the shelf life
-low toxicity
