28 - 183 - PRINCIPLES OF TOPICAL THERAPY Flashcards
Defined as the uptake of compounds by the cutaneous microvasculature
a. Resorption
b. Absorption
c. Skin metabolism
d. Diffusion
A
Occlusion increases drug delivery by __x
a. 10
b. 15
c. 20
d. 25
A
Solutions with added powder, zinc oxide, talc, calamine, glycerol, alcohol and water
a. Shake lotions
b. Suspension
c. Solutions
d. Gels
A
Optimum size of the particles for penetration into hair follicles is between
a. 300-600 nm
b. 300-400 nm
c. 400-500 nm
d. 500-600 nm
A
Percutaneous absorption process occurring in the epidermis, except
a. Diffusion
b. Metabolism
c. Binding
d. Reservoir function
D
three key steps of topical therapy
- topical application
- percutaneous absorption
- binding of the active molecule to its target site
defined as the decrease in drug response over time, is often a result of nonadherence rather than loss of corticosteroid receptor function
Tachyphylaxis
plays the most significant role in determining the diffusion of compounds into the body
Stratum corneum
Parameters That Affect Drug Amounts in Skin Compartments
Defined as the amount of an active ingredient that is still in contact with the nonvolatile constituents of its formulation after the latter had been massaged into the skin surface
Reservoir
Optimum size of the particles for penetration into hair follicles is
300 and 600 nm
analysis of the reservoir of the hair follicles showed that the highest reservoir is on the
Scalp followed by the forehead and the calf
What are the three penetration pathways
(1) intercellular penetration, inside the lipid layers around the corneocytes;
(2) follicular penetration;
(3) intracellular penetration
defined as the uptake of compounds by the cutaneous microvasculature
Resorption
It directly related to the surface area of the exchanging capillaries as well as their blood flow.
Stratum corneum, the rate-limiting barrier to percutaneous drug delivery, is composed of
ceramides, free fatty acids, and cholesterol in a 1:1:1 molar ratio.
By weight, the stratum corneum consists of 50% ceramides (acylceramides being the most abundant), 35% cholesterol, and 15% free fatty acids.
Area with the highest Relative percutaneous absorption of hydrocortisone
Scrotum
considered the most important route for cutaneous drug delivery
intercellular pathway
two main routes for permeation through the stratum corneum
(1) transepidermal and
(2) transappendageal pathways
simple hydration of the stratum corneum enhances the absorption of topically applied steroids by how many times
4 - 5x
amount of topical dispensed from a 5-mm-diameter nozzle onto the tip of the palmar aspect of the index finger to the distal interphalangeal joint skin crease
finger-tip unit (FTU)
One FTU is equivalent to how many mg of topical agent
500 mg
One FTU can cover how many % BSA
2 %
inactive part of a topical preparation that brings a drug into contact with the skin
Vehicle
absorb moisture and decrease friction. Because they adhere poorly to skin, their use is mainly limited to cosmetic and hygienic purposes
Powders
also referred to as a cataplasm, is a wet solid mass of particles, sometimes heated, that is applied to diseased skin
POULTICE
The modern poultice often consists of porous beads of dextranomer. Poultices are used as wound cleansers and absorptive agents in exudative lesions such as decubiti and leg ulcers
semisolid preparations that spread easily, are petrolatum-based vehicles capable of providing occlusion, hydration, and lubrication
OINTMENT
Ointment bases used in dermatology can be classified into five categories:
(1) hydrocarbon bases,
(2) absorption bases,
(3) emulsions of water-in-oil,
(4) emulsions of oil-in-water
(5) water-soluble bases
In pharmaceutical terms, all of these preparations are ointments and are specifically indicated for conditions affecting the glabrous skin (palms and soles) and lichenified areas
Dermatologists commonly refer to the hydrocarbon bases and absorption bases a
Ointments
Dermatologists commonly refer to the water-in-oil and oil-in-water emulsion bases as
Creams
In pharmaceutical terms, all of these preparations are ointments and are specifically indicated for conditions affecting the
glabrous skin (palms and soles) and lichenified areas
Also called oleaginous bases, hydrocarbon bases are often referred to as
Emollients
they prevent the evaporation of moisture from skin, are composed of a mixture of hydrocarbons of varying molecular weights, with petrolatum being the most commonly used (white petrolatum, except for being bleached, is identical to yellow petrolatum).
contain hydrophilic substances that allow for the absorption of water-soluble drugs
ABSORPTION BASES
These ointments are lubricating and hydrophilic, and they can form emulsions.
They function well as emollients and protectants.
They are greasy to apply but are easier to remove than hydrocarbon bases. They do not contain water.
Examples include anhydrous lanolin and hydrophilic petrolatum
A waterin-oil emulsion, by definition, contains how many percent of water
less than 25% water, with oil being the dispersion medium
An oil-in-water emulsion contains how many percent water
greater than 31% water
This type of formulation is most commonly chosen to deliver a dermatologic drug.
OIL-IN-WATER EMULSIONS
contain a humectant (an agent that draws moisture into the skin), such as glycerin, propylene glycol, or polyethylene glycol (PEG), to prevent the cream from drying out.
Oil-in-water emulsions
These formulations are water soluble, do not decompose, and do not support mold growth and therefore require no preservative additives
WATER-SOLUBLE BASES
topical antifungal drugs and topical antibiotics (eg, mupirocin) are formulated in this base.
WATER-SOLUBLE BASES
suitable for facial or hairy areas because after application, little residue remains
Gels
incorporation of high concentrations of powders (up to 50%) into an ointment such as a hydrocarbon base or a water-in-oil emulsion
Paste
The powder must be insoluble in the ointment
dissolution of two or more substances into homogenous clarity
SOLUTIONS
hydroalcoholic solution with a concentration of alcohol of approximately 50%
tincture
nonaqueous solution of pyroxylin in a mixture with ether and ethanol and is applied to the skin with a soft brush
Collodion
nonaqueous solutions of drugs in oil or alcoholic solutions of soap
Liniments
two-phase system consisting of a finely divided, insoluble drug dispersed into a liquid in a concentration of up to 20%
SUSPENSIONS (LOTIONS)
lotions to which a powder is added to increase the surface area of evaporation
Shake lotions
triphasic liquids composed of oil, organic solvents, and water, kept under pressure in aluminum cans
Foam
type of nonadherence that is driven by the patient’s perception of the need for treatment weighed against their concern for toxicities and other costs
Intentional nonadherence
type of nonadherence that results from forgetfulness or lack of knowledge on prescribed regimens
Unintentional nonadherence
refers to when patients do not fill their prescription or initiate treatment
Primary nonadherence
occurs when patients initiate treatment but use the medication poorly
Secondary nonadherence
Secondary nonadherence includes both poor execution (using the medication intermittently) and early discontinuation of treatment.
area with highest barrier function
arm and abdomen
barrier function can be ranked as arm ∼ abdomen > postauricular > forehead
popular skincolored powder composed of 98% zinc oxide and 1% ferric oxide and acts as an astringent to relieve pruritus
Calamine
- they prevent the evaporation of moisture from skin, are composed of a mixture of hydrocarbons of varying molecular weights, with petrolatum being the most commonly used (white petrolatum, except for being bleached, is identical to yellow petrolatum)
hydrocarbon base/ oleaginous bases/ emollients
involve formulating the drug in a solution within a pure propellant
Aerosols
microscopic spheres consisting of a bilayer that encloses an inner aqueous core
Liposomes
a compound that is able to promote drug transport through skin
penetration enhancer
increase the viscosity of products or suspend ingredients in a formulation
Thickening agents
Examples include beeswax and carbomers
