Section 7: Suppositories Flashcards
What are suppositories?
Solid dose forms for insertion into body orifices where they melt, soften, or dissolve releasing drug for local or systemic effect
What are suppositories commonly used for?
Rectal or vaginal insertion
What is special about the size and shape of suppositories?
Easy to insert and remain in place after insertion
What is usually the shape of a rectal suppository for adults?
Bullet-shaped
What is usually the weight of a rectal suppository for adults?
2 g
What is usually the shape of a rectal suppository for children?
Small and more cylindrical
What is usually the shape of a vaginal suppository?
Ovoid/egg shape
What is usually the weight of a vaginal suppository?
5 g
What happens to a suppository after it is inserted?
It melts, softens, or dissolves and medication is released to surrounding tissues
What are rectal suppositories for local effect used to treat?
Pain, inflammation, and itchiness associated with hemorrhoids or other anal-rectal conditions
What do rectal suppositories for local effect usually contain?
Local anesthetics, vasoconstrictors, astringents, analgesics, emollients, and protective agents
Why are emollients often found in rectal suppositories?
Make things softer
What is found in rectal suppositories that treat constipation and why?
Glycerin because it has a local irritating effect and lubricates
True or false: some suppositories contain laxative agents
True
What are vaginal suppositories usually used for?
Local effect, often for an infection
What are less common use of vaginal suppositories?
Contraceptive effects, antiseptics for hygiene, or local delivery of agent to treat infection due to yeast
What are some common systemic conditions that can be treated with suppositories?
- Nausea and vomiting
- Migraines
- Analgesics
- Tranquilizers
What are 3 advantages for suppository systemic use?
1) Bypasses GI tract and first-pass metabolism
2) Drugs irritating to stomach can be given this way
3) Used for patients unable to use oral route
What is a disadvantage to suppository use?
Absorption is erratic with inter-patient variability
What are 2 factors that affect drug absorption for suppositories?
1) Physiological
2) Physicochemical
How long is the adult rectum and what does it contain?
- 20 cm long
- Contains 2-3 mL of inert mucous fluid
Why is absorption efficient in the rectum?
Large surface area and extensive blood and lymphatic vascularization
What conditions can affect absorption in the rectum?
Inflammation, diarrhea, tissue dehydration, and presence of tumours or polyps
What picks up drugs that have been absorbed by the rectum?
Blood and lymphatic vessels
What is the pH of an empty colon?
Neutral, with little buffer capacity
True or false: the ionic form of the drug will be affected when it is administered via a suppository
False, the ionic form will not be affected
What physicochemical properties affect absorption of suppositories?
- Solubility
- Partition coefficient
- Particle size
What properties of the base of a suppository affect absorption?
- If it melts or dissolves
- If it is hydrophilic/hydrophobic
What MUST a suppository base to?
Must remain solid at room temperature but soften, melt, or dissolve at body temperature
What is the best suppository base for fat-soluble drugs and why?
Cocoa butter because it melts readily at body temperature but is immiscible with colonic fluid
What is the best suppository base for lipid-soluble drugs?
Water soluble polyethylene glycol
What are the 2 types of suppository bases?
1) Oleaginous and water soluble
2) Miscible
What is generally used in oleaginous bases?
Cocoa butter
At what temperature range does triglyceride melt?
30-36 C
What happens when cocoa butter is heated?
It forms polymorphs
What happens when cocoa butter is heated beyond its melting point?
It forms alpha polymorphs, which is liquid at room temperature
What material can be added to cocoa butter to lower its melting point?
Phenol
What is an advantage to using semi-synthetic oleaginous bases?
Do not form low temperature melting polymorphs
What are 2 examples of semi-synthetic oleaginous bases and what are they made of?
1) Fattibase – triglycerides from palm and coconut oil
2) Witepsol – triglycerides of C12-C18 saturated fatty acids
What type of oleaginous bases are good for rectal irritation and why?
Semi-synthetic because it had soothing emollient properties
What are 2 examples of water soluble and miscible bases?
1) Polyethylene glycols
2) Glycerinated gelatin
What is unique about polyethylene glycol?
Comes in a variety of molecular weights, ranging from 200-8000, with lower values being liquid
What does a higher value PEG correspond with?
Higher melting point
Normally, is one PEG used or is a combination used and why?
A combination is used so they can fuse and incorporate the medication
How does a PEG mixture release medication?
Slowly dissolving
PEG is hydroscopic. What does this mean?
It needs to be protected from moisture; but must be moistened just prior to use otherwise a stinging sensation will ocur
What type of base is usually used for vaginal inserts?
Glycerinated gelatin
What does glycerinated gelatin consist of?
20% gelatin, 70% glycerin, and 10% water
How does glycerinated gelatin release medication?
Slow, and through softening and dissolution
True or false: glycerinated gelatin is not miscible with vaginal secretions
False, the two are miscible
What is glycerin base composed of?
85% glycerin, 9.5% sodium stearate, 5.5% water
What are the 3 ways to prepare a suppository?
1) Molding
2) Compression
3) Hand rolling and shaping
What is the most common method of suppository preparation?
Molding
True or false: when preparing a suppository, the least possible amount of heat is used
True
True or false: when preparing a suppository, it is best to melt the base right on the hot plate
False, it is best to melt in a water bath
How are medicinal substances incorporated when preparing a suppository?
- Mix with some molten base using spatulation
- Stir into molten base and remove from heat
When making a suppository, what ingredients are the last to be added?
Labile or volatile ingredients
What are 2 tips to use when pouring suppository mixture into molds?
1) Stir while pouring just above congealing temperature to prevent material from settling in tip
2) Pour small excess to allow for contraction
_____ molds should be lubricated prior to use
Metal
When should excess material be scraped away when preparing suppositories?
After completely cooled, but before opening the mold
Why should excess mixture be prepared when making suppositories?
To allow for losses
What are the 2 types of suppository molds?
1) Metal
2) Plastic
How should suppositories containing glycerin be stored?
- In glass or otherwise protected from moisture
- May need refrigeration
How should suppositories containing PEG be stored?
Keep away from moisture
How should suppositories containing cocoa butter be stored?
Individually wrapped to prevent adhesion
What should the patient be counselled on when using suppositories (4 points)?
1) Ensure all wrapping is removed prior to use
2) Tip inserted first
3) If half suppository prescribed, cu length-wise
4) Dip PEG or glycerin based products in water prior to use to avoid burning sensation
What are 3 common calculations that need to be done when preparing suppositories?
1) Calibrations
2) Base displaced by medication
3) Amount of base and medication needed
What is an important note about base displaced by medication calculations?
Suppositories with a mass of 2 g and a drug load less than 100 mg, the mass of base being displaced is generally insignificant and doesn’t need to be considered
Can tablets be used as the drug source for suppositories?
Yes, but must take into account the weight of excipients
What is density factor usually for?
Cocoa butter
What does density factor allow for?
Calculation of how much base will be displaced by drug
What is the formula for density factor?
df = weight of drug / weight of base displaced
