Eye crazie (Exam 3) Flashcards
what are gels?
-semi-solid dosage forms
Gels: consist of a matrix formed between hydrogen bonds between: (4 things **)
- gel base/gel base
- gel base/ active ingredient
- micelle/micelle
- viscosity primarily due to hydrogen bonds not molecular weights
Gels & their organic matrix *
- may temporarily be interrupted by heat (viscosity can change with varying temps)
- may be permanently be destroyed by alcohol
what is the purpose of gels?
- vehicle for topical, transdermal, IM or oral preps
- achieve high viscosity with low molecular weights
Gels must be soluble in body fluids or able to melt at body temp, whats the exception?
hemostatic gelatin: used during surgical procedures, so in order to maintain its strength through the whole procedure - it cant be allowed to either melt at body temp or to dissolve in bodily fluids
Where can i put some gel?
- used internally: Amphokel tablets/capsules: not suspension (aluminum hydroxide)
- used vaginally: metrogel (metronidazole)
some examples of topical gels:
- hemostatic gelatin
- Americaine/hurricaine (benzocaine)
- campho-phenique (camphor/phenol)
- erygel (erythromycin)
some examples of transdermal gels
-clonidine, gabapentin, ketamine, lidocaine, indomethacin, prochlorperazine, scopolamine
gels used topically for local effect
-ketoprofen PLO
gel dosing things *
need:
-specific dose - by volume (mg/ml)
apply 1 ml to chest tid or apply contents of 1 syringe bid
-caregiver should wear gloves!
gel- extemporaneous prep considerations for non-organic based gels
- order of incorporation **v important- diverting from the plan can very easily render the product useless
- topical
gel- extemporaneous prep considerations for organic based gels
- order of incorporation (lipo/hydro phase) = emulsion
- shear forces (help the formation of micelles)
- micelles
- transdermal
administration dead space
-1 extra dose of compound: used to fill dead space of the storage and administration syringes
USP def of ophthalmic preps
-essentially free from foreign particles, suitably compounded & packaged for instillation into the eye
USP 797 def of ophthalmic preps*
basically they need to be sterile preparations
what is the purpose of ophthalmic preparations*
- administration of medication to the eye (ocular tissues)
- lubrication (of the ball and socket joint)
- cleansing
do ophthalmic preparations have local effect?*
yes!
but can have systemic absorption: always UNDESIRED = GI coupling (happens via lacrimal ducts connecting the eye to the back of the throat where tears drain into the GI system)
& epithelial absorption
what is the capacity of the eye?*
- 1 gtt/eye (liquids)
- 50 mg/eye (ointments)
dosage forms of eye drops(4)
- solutions: aqueous, ex: atropine 1% w/v
- ointments: white petrolatum & mineral oil, ex: tetracycline HCL 3% w/w
- suspensions: suspending agents, ex: prednisolone 1%
- gels: a solution which forms a gel upon administration, ex: timolol
special considerations for ophthalmic preps*
- pH: 7.4 (ideal)
- tonicity: ~ 277 millimolar
- sterility? yes bish
- preservation: maybe, most times yes
what are the tolerable ranges of pH for eye drop?
6-5-8.5 , if outside of this range = discomfort/stinging or can lead to corneal/tissue damage
how is a tonicity/concentration measured?
via moles of solute particles per liter of solution
mole = avogadros # = 6.022 x 10^23
**tonicity dictates colligative properties (4)
- osmotic pressure
- freezing point depression
- boiling point elevation
- vapor pressure
- colligative properties depend only upon the number of solute particles in solution, not the SIZE of those particles
what is freezing point?*
the temperature at which a liquid freezes: unites = degrees C (absolute value)
what is freezing point depression? *
-the number of centigrade degrees below the freezing point of water (zero C) at which a liquid freezes, units = C degrees
what is the freezing point depression for water?
-freezing point is depressed 1.86 centigrade degrees for every mole of particles per liter of solution
What 2 reasons could there be for the exception of hyper/hypo tonicity being unavoidable?*
- drug stability issues
- therapeutic dosing concerns
what is the mM tolerable range for eye drops?*
200-600 mM
-outside of that range can cause discomfort, stinging and tissue damage
what are the I values? or what is the pattern at least?*
non-electrolytes = 1.0
2-ion electrolytes = 1.8
-then add .8 to each on to add ions
what is the I value?*
- works for most ionic salts in dilute solutions
- *exceptions: zinc sulfate, I = 1.4
- (moles of solute) X (the I value) = moles of particles in solution
- non-saturation at the indicated concentration is assumed!
SCE method
-pH is not an issue (peep the lectures for that crazy math)
Theorem “A”*
- if you add an isotonic solution (of any volume) to a second isotonic solution (of any volume), the resulting solution will also be isotonic.
- precipitation? drug degradation? reaction? miscible*
V-values*
- the amount of H2O required for the dissolution of 300mg of drug which results in an isotonic solution
- assumptions: contribution of solute to the overall solution volume is negligible
- concentration: 300 mg/V-value
USP method
-pH is not an issue (rest on ya sis)
Sorensen Method
- pH IS an issue - pharmacist has direct control over product pH
- do thee phos and bi phos thing
