Gels Flashcards
ointments are ____% water and ____% oil
less than 20% water and greater than 50% oil
true or false
ointments may be medicated or nonmedicated
TRUE
3 functions of unmedicated ointments
protectants
emollients
lubricants
creams are _____% water and _____% oil
greater than 20% water and less than 50% oil
the term “creams” has recently been restricted to _____ emulsions, or aqueous microcrystalline dispersions of long fatty acid chains or alcohols that are ________ and more cosmetically and aesthetically acceptable
O/W emulsions
water washable
what is vanishing cream
o/w emulsion with lot of water and stearic acid
after applying, the water evaporates and leaves behind a thin residue of stearic acid (or other oleaginous component) on the skin
true or false
creams are more stiff than ointments
FALSE - less stiff
**rank the following from most to least stiff
ointment
paste
cream
most stiff = paste
ointment
least stiff = cream
pastes contain a larger proportion of ______ than ointments
what does this do
solid material
thus, pastes remain in place after applying and are good at absorbing serous secretions
name 2 types of gels
-suspensions made of small, inorganic particles
-larger organic molecules, interpenetrated by a liquid
gels are also called ______
jellies
_____ have higher water content than ____ and _____
gels have higher water content then creams and ointments
advantage of ge;s
can be used for several routes of administration
gels can be ____ or ____ systems
single phase or two phase systems
explain what single phase gels are
large organic molecules uniformly distributed throughout a liquid so that NO APPARENT BOUNDARIES exist between the dispersed molecules and the liquid
explain how gels are thick and viscous
the macromolecules contain a “fishnet” and the water molecules get trapped there
the macromolecules in single phase gels can be characteriized as what 3 things and give ex
-natural polymers (tragacanth)
-semisynthetic cellulose derivatoves (MC)
synthetic polymers (carbomer polymers)
___macromolecules tend to form clumps of particles when dispersed haphazardly in the solvent
hydrophilic
to ensure good dispersion, hydrophilic macromolecules should be…..
added slowly with sprinkling and continuous dipserion
if the gel contains __________, it is called a 2 phase system
small, discrete particles
true or false
2 phase systems are thixotropic
true
ie - they are semisolid when sitting for a while but liquefy when shaken
if the particle size in a 2 phase system is LARGE, what is the gel referred to as?
A MAGMA
**give example of a 2 phase gel system and a 1 phase gel system
2 phase - magma
1 phase - hand sanitizer
***4 examples of gelling agents that can be consumed orally
carbopol934P
MC
HPMC
Na CMC
“carbomers” are the generic name for a family of polymers known as ________
carbopol
*****carbomers form ______ aqueous solutions (around what pH??) and thicken at what pH?
form aqueous SOLUTION (~3pH) and thicken at higher pH (~6) to form a gel
(add neutralizing agent to raise the pH and thus form a gel)
_____are crosslinked polymers
carbomers
the ability of carbomers to hydrate is reduced by the addition of what?
salts (salting out)
explain the salting out effect of carbomers when you apply the gel
when we apply on the skin, the carbomer will get runnier due to high temperature.
we have salty skin. thus, the water will release out (salting out) of the carbomer (gel) where it was trapped and wont be a gel anymore – becomes runny and thin
gelation = hydration
______ derivatives are common gelling agents***
cellulose
all of the cellulose derivatives except _______ maintain their viscosity over what pH range?
except cmc
WIDE PH RANGE
3-11
** which cellulose derivative gelling agent has better solubility in cold water and which is better in hot?
what is the concern with how we handle them when preparing gels?***
methylcellulose more soluble in COLD WATER, sodium cmc more soluble in HOT WATER
thus, when methylcellulose is being used as a gelling agent, sprinkle in HOT WATER 1ST!!! (80-90 degrees C) – insoluble vehicle to disperse the gelling agent nicely – and then cool it down with cold water with moderate stirring to gain viscosity to become a gel
opposite for CMC/sodium CMC – dispersed in cold water 1st to hydrate ans swell, and then heating to 60 degrees C
CMC obtains maximal gelling in how long?
1-2 hours
___________ are copolymers of polyethylene and polyoxypropylene
pluronics (poloxamer gels
**poloxamer gels will form ____ gels
what does this mean?
thermoreversible!!!!!
they are liquids at cool temps (fridge) and gels at room or body temp – if you put back in fridge - becomes liquid
how can poloxamer gels/pluronics be used for IM injections
THERMOREVERSIBLE
when you inject, everything should be COLD (bc will be liquid)
when you inject - will become a gel bc body temp – forms a depot for slow release
explain how PLO gels are made
combining Pluronic F-127 gel (hydrophilic) and a lecithin/isopropyl palmitate solution (lipophilic)
WATER SOLUBLE DRUGS are dissolved in the Pluronic gel (in 1 syringe) and the other syringe will have lecithin/isopropyl
(if the drug was lipophilic you would put with lecitihin)
push the plunger of the 2 syringes back and forth to add shearing stress. this will increase the temp and the pluronic will slowly become a GEL
once all is hard, push to 1 side of the syringe
true or false
Pluronic is a lipophilic component of PLO gel
FALSE
component of PLO gel, but it’s hydrophilic
true or false
when making a PLO gel, lipophilic drugs are dissolved in the syringe with lecithin/isopropyl
TRUE
what is syneresis of gels
SHRINKING
occurs when a gel stands for a while - shrinks naturally and some of the liquid gets pressed out
what is bleeding of gels
liberation of oil or water from gels
bc of deficient gel structure - NOT from the contraction involved with syneresis/shrinking
what is the oppposite of syneresis?
SWELLING
what is inhibition of gels
when gels take up a certain volume of liquid, but NO measurable increase in volume
same as swelling, but volume of the gel does not change
*name 2 gelling agents that have better solubility in cold water
methylcellulose and poloxamers
methylcellulose hydrates and swells in ______ water**
HOT
after methylcellulose is added to hot water, it is cooled to ____ for around ____***
0-10 degrees C for 1 hour
TO COMPLETE GELLATION
CMC is dispersed in ____ water to hydrate and swell, followed by heating to _____, with maximum gelling in how long?**
COLD
60 degrees C
1-2 hours
some gelling agents require a neutralizer (pH adjuster) to create the gel after the gelling agent has been wetted in the dispersing medium
name this gelling agent***
carbomer
*most gelling agents require how long to COMPLETELY HYDRATE and reach max viscosity and clarity
1-2 days (24-48hrs)
adding ____ to some gels decreases their viscosity and clarity
alcohol
VERY IMPORTANT - to be GELS
must have hydration!!!!!! lot of water and swelling
*****WHAT GELLING AGENT IS MOST SOLUBLE IN HOT WATER
sodium CMC
**WHAT GELLING AGENTS NEEDS NEUTRALIZER OR PH ADJUSTER ADDED
CARBOMER
**WHEN GELLING AGENT IS USEFUL TO PREPARE THERMOREVERSIBLE GELS
POLOXAMER
*****BUD FOR COMPOUNDED TOPICAL GELS WITHOUT ALCOHOL/PRESERVATIVES
14 days!
aqueous preparation
*****TRUE OR FALSE
carbomer is the generic name of the family of polymers called pluronics
FALSE
carbomers are generic name for CARBOPOL
pluronics is brand for POLOXAMERS
