Lec 2 Extemporaneous compounding Flashcards
What is extemporaneous compounding?
Medicines made from scratch, individual ingredients mixed together in the exact strength and dosage from required by the patient
-> allows compounding pharmacist to work with the patient and the prescriber to customize a medication to meet the patient’s specific needs
What is mixing by triturations?
- Incorporating FINELY DIVIDED insoluble powders or liquids into a base
- performed on a glass slab or tile
- liquid incorporated by making a ‘well’ into the centre of base, with small amounts of liquid poured into well and mixed in
- avoid air pockets
What is mixing by levigations?
- Incorporation of insoluble COURSE powders into a base- can be called ‘wet grinding’
- the powder is rubbed down with either a molten base or a semi-solid base
- Shearing force with the flat blade of the spatual against the slab needs to be applied to avoid a gritty product
What is the ‘doubling-up’ technique?
- Mixing powder to powder, powder to semi-solid or semi-solid to semi-solid, especially when one amount is much smaller than the other
- Can be done in a motar (powder to powder) or on the slab
- Start with small amount of each, mix thoroughly, then double the volume each time as you continue to add to equal what has been mixed
How to add solids and liquids to a semi-solid base?`
- Place weighed semi-solid base on glass slab
- Place all weighed solids in motar and mix or place on glass slab and mix
- Use doubling up technique to incorporate solids into base using a spatula
- When mixed well in centre, carefully put in small amounts of liquid and mix within the well or score to mix
- Continue until all liquid well mixed in
What is an emulsion?
- A thermodynamically unstable system consisting of at least 2 immiscible liquid phases
- one phase is dispersed as globules (dispersed phase) in the other liquid (continuous phase) stabilised by an emulsifying agent
How do you make an emulsion?
- Using a motar and pestle to mix oil, water and emulsifying agent to make a primary emulsion using dry and wet methods
What gum is used to make oral emulsions?
Acacia Primary emulsion: Oil: Water: Gum - Fixed oils = 4: 2: 1 - Mineral oils= 3: 2: 1 - Volatile Oils= 2: 2: 1
What is the dry gum method?
- Use a clean, DRY motar with a flat bottom
- Drain oil (measure carefully)
- Disperse acacial over oil and mix gently
4, Add water all at once and stir briskly in one direction –> Clicking sound = primary emulsion formed- white in colour - Gradually dilute primary emulsion with vehicle and dissolved ingredients
- Transfer to pre-calibrated bottle and label
What is the wet gum method?
- Add water to acacia gum and mix gentaly to make a mucilage
- Add oil in small maounts to mucilage
- Triturating thoroughly after each addition until a thick primary emulsion is formed
- Stabilise by mixing for several minutes then add other ingredients as for dry gum method
What are some problems when compounding an emulsion?
- Phase inversion
- Incorrect quantities of oil or water used
- Cross contamination of water/oil
- Wet motar used
- Motar too small and curved, head of pestle too rounded- insufficient shear force
- Excessive mixing at first stage with dry gum method and oil
- Diluting primary emulsion too soon and too rapidly
- Poor quality acacia
What is a suspension?
A disperse system in which one substance in the disperse phase is distributed in particulate form throughout another (the continuous phase)
- Suspended solids slowly seperate on standing, and can usuallly be redispersed with shaking but this may be difficult if they form a compacted sefiment
How to make a suspension base?
- Use motar and pestle to grind tablets
2. Mix with glycerol, syrup or mucilage
How do you dispense powders?
- Use motar and pestle to mix active ingredient with filler using double up method
- Wrap powders and fill capsules
What are capsules?
- solid preparations for oral administration (hard or soft and medicaments enclosed within the shell)
- Soft capsules are formed, filled and sealed in one process and requires specialised equipment
- Give accurate dose and improved stability
- Used for powders, non aq liquids, solutions, emulsions, suspensions or pastes
