The Pharmacist Semester 2 Flashcards
Give examples of semi solid preparations.
Ointments
Creams
Gels
Pastes
What is a transdermal formulation?
Absorbed through the skin to work systemically- more commonly as patches than semi solids.
What is a diadermal formulation?
Works in the dermis or lower with a local effect, useful for anti-inflammatories, anti-itching and local anaesthetics.
What is an epidermal formulation?
Works locally at the surface of the skin, useful in things such as lubrication, UV protection, emollients and antimicrobials.
What is a topical formulation?
An umbrella term for formulations used on the skin such as semi solids, eyedrops, rectal, vaginal or intra-nasal drugs- epidermal and endodermal, local effect.
What are the properties of creams?
Emulsions- contain oil Provide cooling effect on the skin Less greasy- patient friendly Less occlusive- good for macerated skin Require preservatives as they are hydrous- less stable
What are the properties of pastes?
Stiff preparation
Ointments with 30-70% of their mass being powder based
Precise localised treatment
Form thick, impermeable layer on the skin
Less spreadable than other semi solids
What are the properties of gels?
Made up of polymer and have high water content
Drug able to diffuse through gel to site of action
Leave little to no residue on skin
Require stabilisers
Explain the benefits of oily vehicles in semi solids.
Allow occlusive layer to form:
Mineral oils- limited penetration into skin
Vegetable oils- good penetration but can turn rancid
Synthetic oils- water repellent and occlusive
What is the benefit of water miscible vehicles in semi solids?
Added cooling effect and act as absorption promoters.
What do emulsifying agents do in semi solids?
Help oil and water to form a stable, uniform mixture and increase drug penetration.
Give examples of emulsifying agents.
Water in oil: bees wax, lanolin
Oil in water: waxes based on cetostearyl alcohol
Polyethylene glycols: macrogols/carbowaxes
Non-ionic surfactants: sorbitan
What is the role of humectants in semi solids?
Reduce the loss of water from creams and gels e.g. glycerol
What is the role of preservatives in semi solids?
Increase the stability of the preparation e.g. parabens and EDTA
What is the role of antioxidants in semi solids?
Preventing decomposition.
What three things most affect semi solid preparations?
Heat
Light
Micro organism growth
What should be considered when making packaging for semi solid preparations?
Assuring photo-stability.
The packaging should not interact with the formulation.
Give advantages and disadvantages of ointments and pastes.
Stable, occlusive, good for dry skin, less need for preservatives.
Greasy, slow absorption, high oil content preps can be flammable, not to be used on macerated skin.
Give advantages and disadvantages of creams and gels.
Non greasy, more patient friendly, rapid absorption, cooling effect, less additives in gels, can be used on macerated skin.
Susceptible to microbial contamination, require preservatives, less stable (short expiry), short duration of action.
What properties do aerosols for topical application have?
Drug is dispersed in solution/suspension.
Requires propellant such as HFAs, CFCs, butane.
To be stored below 25 degrees.
Aerosols must be shaken before use.
When making semi solids extemporaneously, how much excess should be made?
25%
What is trituration?
Method of incorporating liquids or powders into a semi solid base on a ceramic tile.
What is levigation?
Application of pressure to incorporate powder into a semi solid.
How long should extemporaneous records be kept for?
Legal requirement of a minimum of 5 years
What should an extemp record contain?
Formula and source Calculations and ingredients-checked Names and signatures of all involved with process Date prepared and supplied Expiry and batch no Details of patient and doctor Label
What is stability determined by?
Physical appearance Chemical changes Microbial Therapeutic effect Toxicology
What expiry date should be given if unavailable in the monograph?
Stable preparations (solid internals and externals)- 3 months Unstable preparations (liquids/semi solids)- can be 2-4 weeks
What are the most common preservatives used in aqueous liquids?
Chloroform water/spirit
What reasons are there for coating a tablet?
Protecting the drug
Masking taste/appearance
Easier to swallow
Altering release properties
What are the two types of capsule?
Hard gelatin
Soft gelatin
What do diluents/fillers do in solid dosage forms?
Add bulk e.g. lactose, mannitol
What do binders do in solid dosage forms?
Form granules e.g. gelatin, cellulose
What do lubricants do in solid dosage forms?
Improve flow properties e.g. magnesium/calcium stearate
What do colourants do in solid dosage forms?
For identifications/appearance e.g. E numbers
What excipients are present to give effervescent effect?
Reaction between carbonate and weak acid produces CO2 to break up tablet e.g. sodium carbonate and citric acid
What excipients are present specifically in chewable tablets/solids in liquid preparations?
Sweetners and flavouring
What are the three types of modified release tablets?
Delayed- releases after certain time frame
Enteric coated- pH dependent release
Extended- prolonged/suspended
What are the two most common methods for modified release tablets?
Matrix system- can be split
Reservoir/membrane system- cannot be split
What are the advantages of tablets and capsules?
Stable, accurate dosing, convenient for use, low cost, easy to make, taste can be masked, release can be modified, enteric coating available.
What are the disadvantages of tablets and capsules?
Slow onset of action, 1st pass metabolism, systemic action, side effects, often contain gelatine, difficulty swallowing.
What are the advantages of powders and granules?
Very stable, can be reconstituted to liquids, faster onset of action, accurate dosing in sachets, good for larges doses, easier for those with difficulty swallowing, release in granules can be modified.
When made extemporaneously what is the minimum weight of the contents of a capsule?
100mg- if below a diluent must be added.
What are the three methods for filling capsules?
Punch- pressing capsule into mixture
Capsule machines- use trays to hold capsules
Weighed aliquots- fill capsules individually
Define a solution.
A homogeneous picture of two or more components resulting in a one phase system.