semisolids (week10) Flashcards
skin pH
5.5
main layers
epidermis
dermis
subcutaneous
layers of epidermis
stratum corneum
stratum lucidum
stratum spinosum
stratum germinativum/basale
epidermis cell types/what prod
keratinocytes - produce insol keratin protein and lipids
melanocytes
dendritic (langerhans) cells
Dermis
-matrix of CT
-
-matrix of CT: 75% collagen 4% elastin
- contains BVs and nerves and appendages (sweat glands, sebaceous glands, hair follicles)
-contains fibroblasts, mast cells, histocytes
-SITE OF DRUG METABOLISM
maintians “sink conditinon” due to vasculature
Epidermis
epidermis cells = viable portion of epidermis
stratum corneum dead cells
+forms impermeabble layer
+rss permeation of external cpds
SERVES AS RATE LIMITING factor in absorbtion of drugs
Targets for drmatologicla treatment ()
skin surface startum corneum skin apendages viable epidermis and dermis systemic treatment bia percutaneous absorption
targets for dermatological treatment: skin surface
- camoflauge or cosmetic preparations
-protective films - barriers, sunscreans, antifungal and antibacterial preps (polysporin)
-
targets for dermatological preparations: stratum corneum
emolients and moisurizers
+increase water content
keratolytics (remove dead cells)
skin appendges
antiperspirants (seat glands) - aluminum salts
exfoliants (in acne) - salicylic acid, tretinoin, benzoyl peroxide
depilatories - thioglycolates
antibiotics - clindamycin, tetracyclin, erythromycin
antifungals - clotrimazole, miconazole
targets for dermatological treatement: viable dermis and epidermis
topical steroidal/nonsteroidal antiinflammatory agents
local anesthetic agents
antihistamines/antipruritic
anticancer drugs
target regions for dermatological treatment: systemic treatment by percutaneous absorption
motion sickness - scopolamine
angina - nitraglycerine
hypertension - clonidine
smoking cessation - nicotine
selection of vehicle for optimum bioavailability
- Skin disease or condition
- Rate of the release of the drug from the vehicle (drug favors skin over vehicle)
- Promotion of percutaneous absorption
- Requirement for occlusion
- Short and long term stability of the drug in the ointment base
- Influence of the drug on the consistency of the base
pH above what is irritating to skin
above 8
criteria for dermatological formulations
1) physiochemical criteria
2) cosmetic (aesthetic) criteria
physiochmeical criteria Iderm form)
- 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
criteria for dermatoologic formulations: cosmetic
- Pharmaceutical elegance ——> non-compliance
• Easy transfer from container
• Spreads readily and smoothly
• Leaves no residue
• Adheres to treated area without being tacky or difficult to remove
Dermatologic vehicles (ointments) (5)
hydrocarbon bases absorbing bases emulsifying bases water soluble bases silicone bases
dermatologic vehicles: creams and lotions (2)
O/W emulsitons
W/O emusionts
Dermatologic vehicles powders
dusting powders
dermatological vehicles: liquids
linments
soaks
tinctures
dermatological vehicles: what are they (7)
ointments emmulsions pastels gels aerosols powders liquids
ointments
semisolid preps
hydrophillic or greasy
usually anhydrous
may contain dissolbed or dispersed medicaitons
creams
semisolid preparations, both oil and water
non water washable bases (4)
oleaginous/hydrocarbon
absorption bases
W/O emulsion bases
silicon bases
water washable vehicles (4)
O/W emulsions
gels
hydrophillic bases
emulsifying bases
normal water content of stratum corneum
10-20%
permeability of intact vs diseased skin
intact = good barrier diseased = more permeable
shunt rule
durgs can permeate into the skin by absorption through the appendages
Acid mantle
pH 5.5
dermatological formulations with pH 5.5 are most compatible with skin
bacteriocidal and fungocidal secretions from eccrine and sweat glanes (short chain FAs)
effects of UV light on the skin
UVB - 290-320nm - burns skin
UVA - 300-400nm - less damaging
effect of hot and cold exposure percutaneous abs
hot
- vasodilation, red skin
- more percutaneous abs
cold
- vasoconstriction
- percutaneous abs dec
sink conditions
blood flow through BVs takes drugs that are percutaneously absorbed with it thus maintaining the concentration gradient needed for percutaenous absoption between the formulation and the skin
Pastes
- semisolid preparation
- large portion of solids (20-50%) finely dispersed in a fatty vehicle for external application on the skin
Very stiff - localize materials to defined regions of skin
thick impermeable layer on skin - protective
Lotion
emulsion liquid dosage form
gel
semisolid
-gelling agent provides stiffness
-solution or colloidal dispersion for ext app
gel may contain suspended particals
Properties
- dissolve in water
- good for hairy areas
- water soluble drugs easily encorporated (dissolved in aq phase or dispersed in gel)
occlusion
formation of impermeable layer on skin to prevent evaporation of water
-may be accompagnied by plastic wrap over generally greasy ointments
inc hydration by preventing evaporation of water
enhance percutaneous abs
soften skin (emolient action)
oleaginous/hydrocarbon bases
occlusive
Properties
- greasy
- hydrophobic
- non- water washable
- emolient
advantages
- very stable
- non irritating
- non-sensitizing
- high compatibility with drugs
excipients non water washable bases
1) fats and fized oils
+oils tend to decomp on exposure to air light high T = become rancid
2)Waxes
-esters of FA and fatty alcohols
-Fatty substances with high MP (60-80)
-used as stiffening agents in ointments and creams
emollient properties
non-water washable bases: vehicles
petrolatum (yellow soft parrafin, yellow petrolatum)
white petrolatum (colour bleached)
yellow ointment USP
white ointment USP
zinc ozide ointment USP
Plastibase (polyethylene and mineral oil)
plastibase
gelled mineral oil by addition of polyethylene
unctuous base (stains, difficult to remove)
consistency dosent change over wide T range
useful working T 15-60
excessive heat over 90 destroys
DRUGS RELEASED FASTER BY PLASTIBASE THAN PETROLACTUM
Absorption bases
types: anhydrous lanolin (wool fat) lanolin (hydrous wool fat) lanolin alcohols, liquid lanolin (lanolin oil) hydrophilic petrolatum USP aquabase ointment wool alcohols ointment BP
properties
- hydrophobic
- greasy
- anhydrous (hydrophillic cpnts provide water abs properties)
- add water forms W/O emulsions
absorption bases: anhydrous lanolin (wool fat)
- mix of sterols and lanolin alcohols which impart ability to abs water
- sticky yellow unctuous mass from sheep wool
- can be sensitizing
- -MP 36-42
- water content 0.25%
- can take up to 2x weight in water
- acts as W/O emulsifier
unctuous
stains, difficult to remove
Lanolin (hydrous wool fat)
25-30% water
W/O emulsion - not always used as absoption base
-still take up lim amnts water
Absorption bases: Lanolin alcohols, liquid lanolin (lanolin oil)
purified fractions of wool fat
less tacky than wool fat
what part of wool fat enables the emulsifying properties
wool fat = anhydrous lanolin
its cholesterols and lanolin alcohols impart its ability to absorb water
W/O emulstions
more greasy than O/W
good at removing oil soluble substances from surface of skin
emolient and cleanisng action
ex. cold creams and emolient creams
cold creams
use beeswax-borax in situ emulsifier
OR
cetyl wax of white wax`
Non-water washables bases: pastes
PASTES
pointments containing up to 50% poweder dispersed in fatty base
very stiff and locatlize materials in specific location on skin
thick impermeable layer on skin - protective action
NON WATER WASHABLE BASES: SILICON BASES
FLUID POLYMER WITH SIMILAR PROPERTIES TO HYDROCARBON BASE
HYDROPHOBIC
BARRIER TO PROTECT SKIN (DIAPER RASH, BED SORES)
10-30% CONC IN OINTEMNTS
