Lecture 7: suppositories Flashcards
When are suppositories a reasonable dosage form?
medicated solid, various weights and shapes, intended for insertion into body cavities: rectal, vaginal, urethral use that melts and dissolves at body temperature,
A good alternative for NPO patients avoiding IV access
Why are compounded suppositories often seen as a “last resort”?
- difficult to comopund
- unpredictable absorption
- avoid when narrow therapeutic window (hard to dose)
What are characteristics of an ideal suppository base?
- chemically & phyiscally stable
- nonreactive and stable w/ drugs and auxillary agents
- aesthetically pleasing
- melts and dissolves in the intended body cavity
- nontoxic, nonirittating
- nonbinding w/ drugs
- viscous enough for drug suspension
- thin enough to pour into mold
- shrinks on cooling to easily release from molds
Types of suppository bases (2)
- Oleaginous (fatty)
- Water soluble/miscible
Oleaginous base
MELT
cocao butter
fattibase
Drug absorption affected:
1. oil soluble = slow absorptoin (remains in fattibase)
2. water soluble = rapid absorption
Water miscible base
DISSOLVE
Polyethylene glycol (PEG)
Drug absorption affected:
1. oil soluble = moderate absorptoin
2. water soluble = moderate absorption
Suppository prepration methods (3)
- hand rolling
- compression molding
- fusion molding
hand rolling
less equipment
more skill/practice
fusion molding
melted, poured, cooled
requires density calculations and mold calibrations
Density factor (DF)
Determines how much base will be displaced by drug
ratio of a unit mass of drug powder to the amount of suppository base displaced by the powder
* drug and base specific
* not mold specific
Drug mass: suppository displaced
ex: if 2g of drug = X mL displacement
When is density factor needed to be calculated?
DF only needed when:
1. drug has a quantity dose and used for systemic effect (500mg APAP in 1 suppository, systemic pain)
2. quantity of drug is a relative significant portion of the dosage form (500mg of drug in 2g base)
3. when density difference exists between the base and drug
(density of drug and base not the same)
some can look up, other times calculated
Mold calibration
the average mass of one pure base suppository cast in mold
* mold and base specific
* not drug specific
Cocoa butter weights different amount than PEG made from the same mold
you are JUST working with the base: mold, base specific
What if the drug source for a suppository is a suspension?
- levigation/geometric necessary
- constant stirring during pour
- pour at cool temperature to increase viscosity
Factors to consider for mold lubricating agent
should not be miscible w/ suppository base
1. cocao butter/fattibase –> green soap
2. PEG and glycerin –> mineral oil
Do we ever use water in suppository compounding?
NO, avoid water
1. supports bacterial/fungal growth
2. increases degredation of drugs
3. accelerates oxidiation of fats
4. contributes to brittleness
