Flashcards in methods of formulation 2 Deck (41):
How are insoluble particles dealt with in the lungs?
They are trapped by mucus and swept upwards by the beating cilia to the throat and swallowed
Give 3 drugs given by the lungs for systemic delivery:
- sodium cromoglicate (hay fever)
- isoprenaline (bradycardia)
- ergotamine (migraines)
What is the optimal particle size for aerosols?
>10 = deposited in throat and mouth
<0.5 = exhaled
aerosols are lyophobic colloids, so how are they prepared?
by dispersion or condensation
How are aerosols administered?
by inhalers or nebulisers
What is the difference between an MDI and a DPI?
MDI = generate an aerosol when deployed
DPI = contain capsules/blisters loaded with drug particles
What are nebulisers used for?
treatment of COPD, CF, asthma, antibiotics, opioids
What is local nasal drug delivery used to treat?
nasal congestion, infection, hayfever
What is systemic nasal drug delivery used to treat?
analgesics, erectile dysfunction, vaccines, sympathomimetics (adrenaline, dopamine)
What particle size is good for nasal drug delivery?
Where is the main site of drug absorption for nasal delivery?
epithelium of the nasal turbinates
How do lipophilic drugs cross the epithelium of the nose?
by paracellular diffusion (between cells as oppose to transcellular which is through cells)
What indication does PenFent have that is good?
used to relive breakthrough pain in people already receving opioids on a regular basis
What are the advantages of rectal drug delivery?
- avoids oral route
- taste isn't an issue
- small and large doses can be given
- no protease activity in the rectum
- skilled HCP not needed
What are the disadvantages of rectal drug delivery?
- patient acceptance
- slow and sometimes incomplete drug absorption
- development of proctitis (inflammation) with prolonged use
- problems with leakage and insertion
- short shelf life
- small market size (<1%)
What do the nose, lungs and rectum all have in common?
all have goblet cells which release mucus
What is the pH of the rectum?
around 7.5 (more alkaline in children)
Why can't acidic/alkali drugs not be given via rectum?
As the rectum doesn't have buffering capacity
How does rectal delivery avoid first pass metabolism?
By passing straight to the vena cava
Why is rate and extent of absorption of rectal delivery lower than the oral route?
- limited SA for absorption
- reduced fluid volume, affecting drug dissolution
What is the advantage and disadvantage of using surfactants in rectal drugs?
good because can improve drug delivery and prevent aggregation,
but bad because can cause rectal irritation
depending on the vehicle, a suppository will either...
melt on the mucous layer or dissolve in the rectal fluid
How much do rectal suppositories weigh?
What are the 2 types of bases used in suppositories?
1. water soluble bases (used less)
2. glyceride type fatty acids (natural/synthetic oils such as triglycerides, saturated fatty acids, waxes, fatty alcohols )
Whichever suppository base is used, they should all...?
- have a mtp small enough to be solid after preparation
- melt/dissolve at room temp
- dissolve in the available rectal fluid
- chemically and physically stable during storage
- be non-irritant
- have an appropriate viscosity to minimise leakage
What is the mpt like of PEG bases? And what is a packaging consideration?
high mpt so good for tropical climates but they can oxidise forming peroxides on storage so airtight packaging is needed
Do you want suppositories to be water soluble in a fatty base?
yes - prevents sedimentation, smaller particles means faster dissolution rate
In what 3 ways are suppositories formed?
- hand rolling (small scale)
- compression moulding (semi automated)
- fusion moulding (semi-automated)
What will viscosity enhancers do in suppositories and what are some examples?
slows down drug release (as particles are trapped)
- colloidal silicon oxide, aluminium monostearate
the ideal suppository should weigh... and contain drug particles of ...
3.5g and contain drug particles of 25um
What kind of conditions are lipid based suppositories used to treat?
Why are rectal tablets not used often?
Due to the low amount of water present in the rectum, limiting dissolution of tablets
Rectal tablets which release CO2 can be useful, why?
the gas released, stimulates defecation
Why are enemas good?
- have a large volume enabling drug to reach upper part of rectum and sigmoid colon
What are the local uses of vaginal drug delivery?
anti-fungal - clotrimazole
microbicides - to prevent HIV transmission, chlamydia
What are the systemic uses of vaginal drug delivery?
HRT mainly e.g. oestrogens
(higher bioavailability than oral HRT)
What is the pH of a healthy vagina? why is this?
- due to conversion of glycogen to lactic acid by lactobacillus
Vaginal drug delivery is affected by...?
phase of menstrual cycle
- NOT HPV infection
What type of bases should pessaries be made from?
glycerol-gelatin bases (water soluble to ensure rapid release and miscibility)
What are 'rings' used for?