Test 1- Semisolid dosage forms 1 Flashcards
What is the outermost layer of the skin?
Epidermis
What cells are actively dividing in the epidermis?
keratinocytes
Accumulate at the skin surface to form keratinized horny layer of skin (stratum corneum
What is the stratum corneum composed up?
Keratins
Lipids
What links the 15-25 layers of the stratum corneum?
Intercellular bridges
What does the intercellular space of the stratum corneum comprise of?
Lipophilic matrices alternating with hydrophilic layers
What covers the stratum corneum?
An acidic film made up of emulsified lipids
What does the skin do for the body?
Protect
regulate heat and water loss from the body
The stratum corneum is _____ meaning it swells to 3 or 5 times its original thickness when absorbing water
Hygroscopic
What are the 4 general effects of drugs applied to the skin?
An effect on the skin surface
An effect within the stratum corneum
A more deep seated effect requiring penetration into the epidermis and dermis
A systemic effect by delivery to the vasculature
What are the skin surface effects?
Protective agent (forming film) (deminishing loss)
An action against surface microrganism (anti infectives agent)
A cleansing effect (soap)
What drug effects can happen on the stratum corneum?
Increased moisture of the skin and resulting softening of the skin
What agents increase skin moisturization?
Occlusive agents
How does skin become moistened?
Hydration of dry outer cells (surface films)
Integration of water in the lipid rich intercellular laminae
What agent should be used for someone with psoriasis?
Keratolytic agents
What do keratolytic agents do?
Act to cause a breakup or sloughing of stratum corneum cell aggregates
How does the stratum corneum serve as a reservoir?
Topically applied drugs accumulate due to partitioning into or binding with skin components
What can the reservoir effect do?
Limit the migration of the drug away from the stratum corneum unless the capacity of the corneum is exceeded by providing excessive drug
What are some examples of drugs that exhibit significant skin interaction?
Corticosteroids, extrogens, benzocain, and scoplamine
What is p-aminobenzoic acid?
Sun screening agent that both penetrates and is substantive to stratum corneum cells
In psoriasis vulgaries, _____ play an important role since they are responsible for hyperkeratotic lesions
keratinocytes
What is a principal driving force for diffusion across the skin?
Thermodynamic activity of the permeant in the donor vehicle
What routes for permeation are important through skin?
Transcellular and intercellular
What are the physiochemical properties affecting drug permeation through the skin
Low molecular weight
Increased but balanced log P value
Solubility
How can a formulation alter the properties of the skin?
Enhance or retard permeation of a drug by increasing or decreasing its diffusivity and or solubilitywithin the stratum corneum
What is percutaneous absorption influenced by?
Physical and chemical properties of the active ingredient
Concentration
Vehicle
Variations in type of skin
When does cutaneous penetration of an active ingredient become enhanced?
Low molecular weight
Lipid soluble
Nonpolar
What are semisolid dosage forms intended for?
Topical application
When medicated what kind of effects do semisolid dosage forms give?
Local and systemic effects
When un medicated, what are semisolds used for?
Their physical effects as protectants or lubricants
What does occlusion usually mean?
The skin is covered directly or indirectly by impermeable films or substances. (these usually contain fats or polymer oils)
TF: Occlusion increases permeability and decreases the mean residence time
true
What are ointments?
Semisolid preparations intended for external application to the skin or mucous membranes
What are ointment bases?
Vehicles or diluents for drugs designed to facilitate drug transfer into the skin
What are the 4 groups of ointment bases?
Oleaginous bases
Absorption bases
Water removable bases
Water soluble bases
What effect does oleaginous/hydrocarbon bases have?
Have emollient/smoothing effect
Skin softening and moisturization effect
How do oleaginous bases give a moisture effect?
Act as humectants by preventing moisture from escaping
Effective as occlusive dressing
Remain on skin for a long time without drying out
Why are oleaginous ointments difficult to wash off?
They are immiscible with water
What are levigating agents?
Mineral oil for oleaginous bases and glycerin for aqueous baes
Used to incorporate powdered substances into hydrocarbon bases
What are some examples of hydrocarbon ointment bases?
Petrolatum
Yellow ointment
White petrolatum
White ointment
What is petrolatum?
Purified mixture of semisolid hydrocarbons obtained from petroleum
What are other names of petrolatum?
Yellow petrolatum or petroleum jelly
hat is a commercial product of petrolatum?
Vaseline
What is the color variation of petrolatum?
Yellowish to light amber
What is another name for white petrolatum?
White petroleum jelly
What is a commercial product of white petrolatum?
White vaseline
What color is white petrolatum?
It doesnt have one it is completely decolorized petroleum
What is the purpose of Petrolatum?
Used as an ointment base
What is another name for yellow and white ointment?
Simple ointment
What is simple ointment?
Purified wax of the honeycomb bee (bleached if white)
What are the parts of simple ointment?
5 parts yellow or white wax
95 parts petrolatum
What is the purpose of simple ointment compared to petrolatum?
It has a slightly greater viscosity than plain petrolatum
What are the two types of absorption bases?
Those oleaginous bases that contain water in oil emulsifying agent, permitting aqueous solution incorporations
Those that are water in oil emulsion naturally permitting incorporation of additional quantities aqueous solution
What are absorption bases used for?
Emollients/soothing agents
Absorption bases do not provide _____
Occlusion
Absorption bases absorb water up to ____ times their weight to incorporate a ____ soluble drug
2-3
water
Why are absorption bases used as pharmaceutical adjuncts?
To incorporate small volumes of aqueous solutions into hydrocarbon bases (nonpolar)
First incorporate it into absorption base then into hydrocarbon base
What are the contents of hydrophilic petrolatum
Cholesterol
Stearul alcohol
White wax
White petroleum
What is lanolin obtained from?
Wool of sheep
What is lanolin?
A purified wax-like substance, deodorized and decolorized
Lanolin contains no more than ____% water?
0.25
How is additional water incorporated into lanolin?
Mixing
What is modified lanolin?
Processed to reduce free lanolin alcohols and any detergent and pesticide residues
What are water-removable bases?
Oil in water emulsion
What is another name for water-removable bases?
Water washable ointment bases
Easily washed
What is the external phase of the water removable base emulsion?
aqueous
What can water-removable bases be diluted with?
Water or aqueous solution
What does hydrophilic ointment contain?
It is a water removable ointment base that has stearyl alcohol and white petrolatum
Purified water
Sodium lauryl sulfate
Propylene glycol, methyl paraben propylparaben
What phase is purfied water in hydrophilic ointment?
Aqueous
What phase is stearyl alcohol and white petrolatum in hydrophilic ointment?
Oleaginous phase
What is sodium lauryl sulfate in hydrophilic ointment?
Emulsifying agent
What is propylene glycol and parabens in hydrophilic ointment?
Antimicrobial preservative
What do water soluble bases NOT contain?
Oleaginous components
Water soluble bases are _____ water washable
Completely
Why are water soluble bases completely water washable?
Because they soften greatly with the additionof water
What are water soluble bases used for?
The incorporation of solid substances
What is PEG?
Polyethylene glycol ointment
A polymer of ethylene oxide and water
What do PEGs with molecular weight below 600 look like?
Clear colorless liquids
What do PEGs with molecular weight above 1000 look like?
Wax like white material
What do PEGs between 600-1000 MW look like?
Semi solids
What are the factors considered in choice of ointment base?
Site of application (dry wet)
Required rate of drug release
Chemical stability of the drug
Effect of the drug on viscosity of the product
Why are drugs prone to hydrolysis not incorporated into water based ointments
To avoid degredation
