Chapter 183- Principles of Topical Therapy Flashcards
Efficacy of topically applied drug depends on 3 things:
- Whether drug was applied
- Delivery of active molecule by its vehicle
- Inherent potency of active molecule
Factors that affect penetration of drug: (4)
- Soluble drug concentration
- Regional variations in skin barrier properties
- Frequency of application
- Effects of vehicle on barrier function
Primary barrier that limits percutaneous absorption of compounds is
Stratum corneum
Topical therapy involves 3 key steps:
- Topical application
- Percutaneous absorption
- Binding of active molecule to target site
Nonadherence to prescribed medicines in chronic conditions is between ___%
30 to 50%
Low absorption does not necessarily translate into low efficacy.
True or False
True
3 compartment model of skin
- Skin surface
- Stratum corneum
- Viable tissue
Most significant role in determining diffusion of compunds into body
Stratum corneum
When a patient applies a dermatologic preparation, the layer of formulation is ___ .
0.5 to 2 mg/cm2
Matching type
- Diffusion
- Reservoir
- Thermodynamic activity
- Binding
- Resorption
- Evaporation
A. Vehicle
B. Stratum corneum
C. Epidermis
D. Dermis
- B>A
- B
- A
- C> B
- C
- A
Amount of active ingredient that is still in contact with nonvolatile constituents of formulation after latter has been massaged into skin surface
Reservoir
Optimum size of particles for penetration into hair follicles is between ___ nm to a depth of 100 to 500 um
300-600 nm
Several paramaters to consider when selecting a formulation (5)
- Thermodynamic activity of the active ingredient
- Amount of compund that can be incorporated into the formulation
- Stability of formulation
- Partition coefficient of active ingredient between the vehicle and the stratum corneum
- Enhancer activity
Percutaneous absorption is proportional to ___
Thermodynamic activity of the compound
Stratum corneum measures __um
10 - 20 um
Arrange the ff reservoir from highest to lowest
Scalp
Forehead
Calf
Scalp» forehead»_space; calf
Three pentration oathways
Intracellular
Intercellular
Follicular
Nanoparticles are stored ___ times longer in hair follicles than in the stratum corneum
10
Accurate and reproducible measurement of skin barrier activity is
Transepidermal water loss
Transepidermal water loss varies __% by site; __% by day of measurement; and __% amongst individuals
8%
21%
35 to 48%
Barrier function ranked from highest to lowest Forehead Postauricular Arm Abdomen
Arm= abdomen»_space; postauricular»_space; forehead
Metabolic processing of ___ is involved in the presentation of allergens to the immune system
Langerhans cells
Metabolic activity is found in (5)
Skin surface microorganisms Appendages Stratum corneum Viable epidermis Dermis
Extent of metabolism in the skin is normally modest only __%
2 to 5%
Uptake of compounds by cutaneous microvasculature, directly related to surface area of exchanging calillaries as well as their blood flow
Resorption
Under resting conditions, only __% of blood flow passes via exchanging capillaries capable of acting as a sink for absorbed compounds
40%
Resorption does not change the rate of diffusion to central compartment after topical application.
True or False
True
For compunds with rapid diffusion across the stratum corneum, resorption limits maximum rate of absorption.
True or False
True
Stratum corneum is composed of __ in a 1:1:1 ratio
Ceramides
Free fatty acids
Cholesterol
By weight, stratum corneum consists of __% ceramides, __% fatty acids, and __% cholesterol
50%
15%
35%
2 main routes for permeation through stratum corneum
Transepidermal
Transappendageal
Most important route for cutaneous drug delivery
Intercellular pathway
Simple hydration of the stratum corneum enhances the absorption of topically applied steroids by ___x
4 to 5
Occlusion increases drug delivery by ___ times the amount of drug delivery when not occluded
10
Occlusion may promote the ff side effects (3)
Infection
Folliculitis
Miliaria
In rare cases, lidocaine toxicity can result to __; prilocaine toxicity can result to ___
Cardiac complications
Methemoglobinemia
Measurement that allows healthcare providers and patients to easily communicate about treatment application
Fingertip unit
1 FTU = ___ of topical agent = ___ BSA
500mg; 2%
Inactive part of a topical preparation that brings a drug into contact with the skin
Vehicle
Examples of emulsfying agents (4)
Cholesterol
Emulsifying wax
Sodium laureth sulfate
Polysorbates
Auxiliary emulsifying agents or emulsion stabilizers: (3)
Cetearyl alcohol
Glycerin monostearate
Polyethylene glycol
Examples of stabilizers/preservatives (5)
Benzyl alcohol Citric acid EDTA Parabens Sorbic acid
Examples of solvents
Alcohol
Water
Examples of thickening agents
Beeswax
Xanthan gum
Petrolatum
Examples of auxiliary agents and emollients
Cetyl alcohol
Stearyl alcohol
Lanolin
Examples of Humectants
Glycerin
Propylene glycol
Sorbitol solution
Glycerin and propylene glycol have the same functions except A. Stabilizer B. Humectant C. Solvent D. Emollients
D. Emollients, only glycerin
Most powders contain __ for antiseptic and covering properties, ___ for lubricating and drying, and __ for improved adherence to skin
Zinc oxide
Talc / magnesium silicate
Stearate
Calamine consists of
98% zinc oxide
1% ferric oxide
Wet solid mass of particles, sometimes heated, that is applied to diseased skin
Poultice or cataplasm
Used as wound cleansers and absorptive agents in exudative lesions such as decubiti and leg ulcers
Poultices
