M8. Semisolids Flashcards
what dermatological treatments target the
skin surface
- camouflage or cosmetic preparations
- protective films -> barriers, sunscreens
- antifungal and antibacterial preparations: Polysporin® (polymyxin B/gramicidin or bacitracin), Neosporin® (polymyxin B/neomycin)
what dermatological treatments target the
Stratum Corneum
emollients and moisturizers ( water content)
keratolytics (to remove dead cells)
what dermatological treatments target the
skin appendages
antiperspirants (sweat glands) -> aluminum salts
exfoliants (in acne) -> salicylic acid, tretinoin, benzoyl peroxide
depilatories -> thioglycolates
antibiotics -> clindamycin, tetracycline,
erythromycin
antifungals -> clotrimazole, miconazole
**treating hair follicles or sebacious glands
what dermatological treatments target the
viable epidermis and dermis
topical steroidal and non-steroidal anti- inflammatory agents
local anesthetic agents
antihistamines/antipruritic
anticancer drugs
what dermatological treatments target the
systemic treatment via percutaneous absorption
motion sickness -> scopolamine
angina -> nitroglycerin
hypertension -> clonidine
smoking cessation -> nicotine
*usually incorporated into transdermal patch
preformulation considerations for dermal delivery systems
- Physicochemical properties of drug and vehicle
Dermatological and cosmetic requirements of the topical vehicle
Stability of drug into topical vehicle
Skin safety
what factors need to be considered for optimal bioavailability
- skin disease or condition
- rate of the release of the drug from the vehicle
- promotion of percutaneous absorption
- reuqirement for occulsion (if yes select a vehicle with occlusive properties)
- short and long term stability of teh drug in the ointment base
- influence of drug on consistency of base
physiochemcial criteria for dermatologic formulations
Stability of the active ingredient
Stability of adjuvants
Rheological properties (consistency, extrudability)
Prevention of loss of water or volatile compounds
Phase changes – homogeneity, phase separation, bleeding)
Particle size, particle distribution of the dispersed phase
Apparent pH
Particulate contamination
cosmetic criteria for dermatologic formulations
Pharmaceutical elegance -> poor product may lead to non-compliance
Easy transfer from container
Spreads readily and smoothly
Leaves no residue
Adheres to treated area without being tacky or difficult to remove
vehicles for dermatolgoical preparations
- Ointments: hydrocarbon, absorption, emulsifying, water soluble, silicone bases
Creams/lotions: oil in water or water in oil emulsions
- pasts, gels, aerosoles, powders
- liquids (liniments, soaks, tinctures)
how many phases are in ointments? creams?
ointments: single pahse behicle
creams: two phase system
what dermatological behicles are washable? Which are not?
- Non water washable: oleaginous/hydrocarbon bases, absorption, W/O, silicone bases
Water washable: O/W emulsions, gels, hydrophilic bases, emulsifying base
ointemtn definition
A suspension or emulsion of semisolid dosage form that contains
<20% water and volatiles
>50% of hydrocarbons, waxes, or polyethylene glycols as the vehicle
for external application to the skin
cream definition
- an emulsion semisold dosage form that contains >20% water and volatiles
<50% of hydrocarbons, waxes, or polyethylene glycols as the vehicle
for external application to the skin
definition of a paste
semisolid dosage form
contains a large proportion (i.e. 20-50%) of solids finely dispersed in a fatty vehicle for external application to the skin
definition of dermatological vehicle
An emulsion liquid dosage form for external application to the skin
definition of a Gel
A semisolid dosage form
contains a gelling agent to provide stiffness to a solution or colloidal dispersion
external application to the skin
gel may contain suspended particles
topical syspension
liquid dosage form that consists of a solid suspended in a liquid vehicle in a two- phase system for external application on the skin
describe a topical solution
A clear homogeneous liquid dosage form for external application to the skin
what are the properties of non water washable base
Hydrophobic
Greasy
Non-water washable
Occlusive
Emollient
what are the advantages and disadvantages of non water washable bases
- Advantages
- very stable vehicles
- non irritating
- non sensitizing
- high compatibiltiy with drugs
- Disadvantages
- greasiness
- stain clothing
- difficult to remove
- low patient acceptance (<< emulsion bases)
what are the effects of non water washable bases
- Increased hydration (by preventing evaporation of water from the skin)
- Enhanced percutaneous absorption
- Softening of the skin (emollient action)
what is occlusion and how is it accomplushed
- formation of an impermeable layer on the skin to prevent evaporation of water
- can be accomplished by plastic wrap over generally greasy ointments
excipeints used in non water washable bases
(greasy thigns you add)
- Fats and fixed oils
- mono, di and tri glycerides
- oils tend to decompose on exposure to air, light and high temp
- become rancid
- ex: veg oils (peanut, sesame seed, olive, cottonseed, almond, corn
- )
- Waxes
- Esters of fatty acids and fatty alcohols
- fatty substances with high melting points
- used as stiffening agents in ointments and creams to inc viscosity
- ex: spermaceti, cetyl esters wax, white wax, yellow wax, hard paraffin
base (vehicles) for non water washable bases
*petrolatum and white prteolatum)
- Yellow ointment
- yellow wax and petrolatum
- White ointment
- white wax and white petrolatum
- Zinc oxide ointment
- zinc oxide, mineral oil and white ointemnt
Plastibase
aka oleo gel
- oleaginous/hydrocanbon base -> non water washable
- made of polyethylene and minteral oil tha tyou melt together
- can be used to get drugs to be released faster
what are properties of asorption bases
- non water washable
- hydrophobic, greasy
- anhydrous; hydrophilic components provide water adsorbing properties
- upon water addition form W/O emulsions
examples of absoroption bases
- Anhydrous lanolin (wool fat)
- mix of steriols ( cholesterol, lanosterol, dihydrocholesterol) and lanoin alcohols (give ability to absorb water)
- can be sensitizing
- LOW WATER CONTENT 0.25%
- can take up to 2x weight in water
- W/O emulsifier
- Lanolin
- 25-30% water
- W/O emulsion -> not always used as absorption base
- can still take up limited amounts of water
- other ex: wool alcohols ointment, aquabase, hydrophilic petrolatum, lanolin alc
W/O emulsions as non water wahsable bases
more greasy then O/W emulsions
emollient cleaning action
capable of absoring oil soluble compounds from skin (ex make up removers)
ex: cold creams (waxes with borate form in situi emulsifiers)
ex: emollient creams like rose water ointment (waxes and borate)
pastes as non water washable bases
*hydrocarbon base with alrge amount of solid that is insolble in paste -> levigation to prepare
- ointments containing up to 50% powder dispersed in fatty base
- very stiff consistency -> localize amterials to defines areas of the skin
- form a thick ipmermeable layer on the skin -> protective action
ex: zinc oxide paste and lassars paste (zinc oxide, starch (powders) and petrolatum
silicon bases as non water washable bases
- fluid polymers with porperties simialr to hydrocarbon bases
- hydrophobic
- used as barreir to protect the skin (diaper rash, bed sores)
- concentration in ointments 10-30%
ex: Dimethicones (polydimethylsiloxanes)
*water repellant properties and good lubricant
O/W emulsions as water washable abses
- water washable
- soft
- non occlusive
moisturizing (inc water content -> restores skin hydration)
penetration enhancement of drug compounds
ex: hydrophilic ointment, vanishing cream, cleansing cream
hydrophilic ointment
O/W emulsion
- sodium laurylsulfate = surfactant
- preservatives: methyl (hydrophilic) and propyl (lipophilic) parabens
- stearyl alc and white petrolatum as oil
- propylene glycol as aq phase
vanishing cream
water washable base
- steric acid + KOH = in situ emulsifyer
- smooth easy to apply -> leaves no residue
cleansing cream
O/W emulsion for water washable base
- stearic acid and triethanolamine -> in situ emulsion
- stearic acid, mineral oil and anhydrous lanoiln contribute to oil phase
Gels as water washable bases
- liquid rich, two component semi- solid colloidal systems
- antural or synthetic polyers form a 3D matric through hydrophilic liq
- dissolve in water and good for hairy areas
- Water-soluble drugs are easily incorporated either dissolved in the aqueous phase or dispersed in gel
ex of gel forming materials
Natural gums: tragacanth, agar, pectin, alginates
Semi-synthetic or synthetic polymers: methylcellulose, hydroxymethylcellulose, hydroxypropylcellulose,
Synthetic polymers: carbopol
Clays: bentonite
water washabe gel bases examples
- Hydroxypropylcellulose (HPC) gel
- HPC + water =-> prepare by hot or cold method
- Zinc oxide gel
- carbomer 934P
- sodium hydroxide (10% solution)
- zinc oxide
- water
what are hydrophilic bases? What are their properties
- water soluble baess usually made by condensation of polymers of ethylene oxide
- ointment like(soften or melt on skin)
Non-occlusive, mix with skin exudates
Do not stain clothes (greaseless)
Non-irritant
Chemically stable: do not hydrolyze, deteriorate, do not support mold growth
Cannot take up more than 8% water (loose consistency)
advantages and inompatabilities of hydrophilic bases
- Advantages
- anhydrous -> useful for drugs that hydroluze
- fod patient compliance -> non staining, non occulsive
- Incompatibilities
- phenoles, iodine, KI, tannic acid, ailver, Mercury and bismuth salts
- reudce antimicrobial activity of quaternary ammonium compounds and parabens
- inactivate bacitracin and penicillin
ex of hydrophilic bases
- Polyethylene glycol ointment USP
- low an dhigh MW polyethylene glycols
- if 200-700 0> liquid
- if MW > 1000 increasingly solid (flaky)
- low an dhigh MW polyethylene glycols
emulsifying bases (ointment) as water washable bases
- anhydrous bases containing O/W emulsifying agents
- cream like
- miscible with water
- self emulsifying
types: anionic, cationic or non ionic agetns
ex of emulsifying bases
- emulsifying pointment BP
- liq paraffin, emulsifying wax and white petrolatum
