D3-D4 Powder-based medicines Flashcards
what are bulk powders?
several doses packed in a container suitable for the route of administration
give some examples of bulk powders
- a plastic bottle containing bulk laxative powder
- canister containing an anti fungal dusting powder for athlete’s foot
- nasal spray with a tip that can be inserted into the nose to squirt 1 dose of the medicine up a nostril
how can oral bulk powders be packed? how can they then be taken?
- in a jar or vial
- spoonfuls of powder dispersed in water, milk or sprinkled onto food
- reconstituted water before dispensing (eg. antibiotics for children)
why is it a good idea to reconstitute powders in water before taking? in terms of stability
- liquid can’t be stored for a long time as it’s sensitive to water and hydrolysis
- stored as dry powder then water added before dispensing (can then be stored for 1-2 weeks)
describe what wrapped powders and sachets are
- one single dose of powder mixture packed in a sealed small bag made of paper, foil or plastic
what are the advantages of wrapped powders / sachets?
- more accurate dosing and more convenient (no need to measure with a spoon)
- better protection against moisture by sachet packet
what are the benefits of powder medicines?
- easier for patients who have difficulty swallowing tablets / capsules
- more stable than liquid medicines (less chemical degradation and low risk of microbial growth)
- good way to give large doses of drug by mouth
- fast dissolution and fast action
state 3 issues with powders
- moisture
- flow
- mixing and separation
explain the issue of moisture with powders
- powders adsorb water (hygroscopic)
- can dissolve during processing and storage (deliquescent)
- can stick together (caking) - forms lumps
- must be protected against moisture by suitable packaging and storage in dry condition
explain the issue of flow with powders
- poor flow will lead to inaccurate / inconsistent packing
state the 4 factors that affect ‘flowability’ of powders
- size
- shape
- moisture
- surface charge
explain how size affects flow in powders
- large particles flow better than small
- small have higher SA:V ratio so more contact points between them and the machinery
explain how shape affects flow in powders
round particles can roll more easily so flow better
explain how surface charge affects flow in powders
charge should be avoided otherwise electrostatic attraction could occur between particles and equipment and prevent efficient flow
explain the issues of mixing and separation in powders
- poor mixing will lead to inaccurate / inconsistent dosing
- powder mixes can unmixed during movement (eg. transport, mixing, pouring)
- small particles can fall through gaps made by larger particles so if drug is a small particle, the concentration will be higher at the bottom than the top
how can mixing and separation issues in powders be solved?
- equalise particles sizes (by grinding and sieving)
- mix equal amounts of powders (geometric mixing, mix the same amount of powders and mix sequentially)
- granulation
what is granulation? what can be done with granules?
- powders are bound together to form larger particles, usually spherical
- contain drug and excipients
- packed into bulk containers, sachets etc.
- filled into capsules
- compressed into tablets
what is the differences between dry and wet granulation?
- dry: dry powders compressed by metal rollers
- wet: powder mixture is wetted with a solution of polymer ‘binder’
describe the role of bulking agents in bulk and wrapped powders giving their function and some examples
- add bulk as the drug may only be a few mg
- patients can’t take a tiny amount of powder
eg.
glucose
lactose
sorbitol
starch
cellulose
talc
describe the role of granulating agents in bulk and wrapped powders giving their function and some examples
- bind powders into granules
eg.
water soluble polymers such as PVP
pre gelled starch
describe the role of effervescent mixtures in bulk and wrapped powders giving their function and some examples
- produce CO2 for faster dissolution
eg.
citric or other fruit acids with carbonates or bicarbonates