D3. Polymers and oral liquid dosage forms Flashcards
what are macromolecules?
Macromolecules are molecules composed of a large number of atoms
What are polymers?
Polymers are substances of a high molecular weight consisting of repeating monomer units
what are defoaming agents?
Defoaming agents are used to relieve trapped wind / bloating
Lower the surface tension of gas bubbles
Example on ONE NOTE
Describe Simeticone
-Polydimethylsiloxane (PDMS)
-Homopolymer: all of the monomeric units are the same
-Linear
-defoaming agent
what active ingredients are in raft forming agent, Gaviscon (Double Action)
Sodium alginate
Sodium bicarbonate
Calcium carbonate
Describe the mode of action for raft forming agents
-Alkali metal salts of alginates, e.g. Na alginate, are water soluble
-If pH drops below 3.5 (the pKa of alginic acid) – alginic acid precipitates as a gel
-The precipitate swells and can absorb up to 100 times its own mass in water
-Many alginate-based medicines also contain bicarbonate or carbonate
Many alginate-based medicines also contain bicarbonate or carbonate. What does this do?
-The bicarbonate or carbonate produces carbon dioxide
-The precipitate/gel traps the carbon dioxide gas, which produces a low density raft that can float on the stomach contents and prevent stomach contents from refluxing into the oesophagus
Gaviscon cool liquid contains?
one note
NOTE THE EXCIPIENTS USED
Describe carbomer excipient
-Variety of uses: emulsifying agent, bioadhesive polymer, suspending agent, viscosity-increasing material
-Inclusion increases the viscosity of the formulation
-Enhanced physical stability of medicine
-Synthetic high molecular weight homopolymers of acrylic acid
-Crosslinked
-pH = 2.5 – 4.0 for a 0.2% w/v aqueous dispersion
Describe parahydroxybenzoates (parabens) excipient
-Antimicrobial preservatives – a mixture of different parabens often employed as this enhances activity
-Less active at higher pH values when thephenolate ion is more likely to form
-Methyl- derivative has a higher aqueous solubility than the propyl- and butyl- esters
-The longer chain esters have a greaterantimicrobial activity
Describe sodium saccharin excipient
-The sodium salt has a greater aqueous solubility than saccharin
-300 – 600 times sweeter than sugar
-Extensively used food and beverages as well as pharmaceuticals
-Suitable for diabetic patients
-Much debate over the safety of saccharin but it is now generally regarded as safe (GRAS) by the US FDA
-Metallic /bitter aftertaste reportedly noted by 1 in 4
Describe flavourings used in gaviscon
-Mint flavour no. 4
-Mint flavour no. 5
-Mint flavourings are traditionally used for indigestion and heartburn remedies
-Peppermint oil is used to relieve irritable bowel syndrome
Describe sodium hydroxide excipient
Included to adjust the pH
At low pH values (below the pKa of alginic acid) the alginate may precipitate; also maximum viscosity at pH 5 – 9
Acidic carbomer will reduce the pH of the formulation so NaOH is required to raise the pH
Competing requirements: aqueous parabens solutions are unstable at pH > 8
Ester hydrolysis
Describe pure water excipient
The ideal vehicle
Describe peptac peppermint liquid
Gaviscon is the branded (innovator) product and peptac is the generic alternative.
What are the similarities between Gaviscon and Peptac peppermint liquid?
Active ingredients are the same
What are the differences between Gaviscon and Peptac peppermint liquid?
Many excipients are the same but there are some different
ONE NOTE
Describe peppermint oil excipient
-Ph. Eur. 7: It is obtained by steam distillation from the fresh overground parts of the flowering plant of MenthaXpiperita
-It is a colourless, pale yellow, or pale greenish-yellow liquid with a characteristic odour and taste followed by a sensation of cold. Miscible with alcohol and with dichloromethane
Describe Isopropyl alcohol excipient
-Isopropyl alcohol probably required as a cosolvent
-Addition of isopropyl alcohol will make the formulation slightly more lipophilic
Describe Ethyl parahydroxybenzoate and Butyl parahydroxybenzoate excipients
-Methyl parahydroxybenzoate replaced with the more lipophilic ethyl- derivative
-Butyl parahydroxybenzoate (more lipophilic that the other parabens) is therefore included
Describe stability of peptac peppermint liquid
ONE NOTE
Describe the different materials to package peptac peppermint liquid?
-Glass:
Non-reactive and totally impermeable
BP; Appendix XIX B. Glass Containers for Pharmaceutical Use
-High-density polyethylene (HDPE):
Not impermeable to vapours
There have been concerns about the compatibility of plastics and parabens for years
Methyl parahydroxybenzoate probably acceptable with HDPE containers
-Polyethylene terephthalate (PET):
Less permeable to oxygen than HDPE
Parabens absorption has caused concerns
What are the two main types of glass used in pharmaceutical packaging?
-Neutral glass (Type I) is a borosilicate glass containing significant amounts of boric oxide, aluminium oxide alkali and/or alkaline earth oxides
-Soda-lime-silica glass (Type II or III) is a silica glass containing alkali metal oxides, mainly sodium oxide and alkaline earth oxides, mainly calcium oxide.
-Alkali components may leach from glass causing chemical instability
Describe the stability of peptac peppermint liquid
Do not store above 25 degrees as:
-Microbial growth
-Preservative hydrolysis
> 60 C alginate depolymerisation
Do not refrigerate or freeze as:
-Na alginate solubility issues
-Freezing causes caking
