Pharmacology Flashcards
Immunologically-mediated skin reactions are dose-dependent. True/False?
False
All or nothing!
Non-immunologically-mediated skin reactions can be dose-dependent. True/False?
True
How do urticarial drug eruptions usually arise?
IgE-mediated hypersensitivity or drug-induced mast cell degranulation
Which drugs tend to cause pustular/bullous drug reactions?
Glucocorticoids
Androgens
Hypertensives
Fixed drug eruptions are well-demarcated and round. Which drugs are commonly associated with this?
Tetracycline antibiotics
Paracetamol
NSAIDs
Carbamazepine (anti-epileptic)
What are the 3 major routes of drug administration through the skin?
Topical
Transdermal
Subcutaenous
What is the single most important barrier to drug administration?
Stratum corneum (made up of corneocytes)
The stratum corneum is made up similar to a “bricks and mortar” model. What are the bricks?
Corneocytes embedded in filaggrin that are held together by corneodesmosomes
The stratum corneum is made up similar to a “bricks and mortar” model. What is the mortar?
Hydrophobic layer made up of intercellular lipids
Is the stratum corneum hydrophilic or lipophilic?
Lipophilic
Absorbs lipid-soluble (hydrophobic drugs)
The principle mechansim of drug penetration of the stratum corneum is transcellular (across the stratum corneum). True/False?
False
Principle mechanism is intercellular (tortuous course between corneocytes)
Drug vehicles are normally used in topical administration of drug (for local effect). What are vehicles?
Pharmacologically inactive substances that “carry” the drug
List some examples of drug vehicles
Ointments Creams Gels Lotions Pastes and powders
Rate of absorption of a topically administered drug = ?
J = Kp x Cv Kp = permeability coefficient Cv = concn of drug in vehicle
A drug must exit its vehicle if it is to penetrate the stratum corneum. True/False?
True
The bigger the Km of a drug, the better it will enter the skin. True//False?
True
Lipophilic drug in a hydrophilic vehicle absorb poorly in skin. True/False?
False
They absorb very well
Lipophilic drug in a lipophilic vehicle absorb very well in skin. True/False?
False
While they will absorb, the drug will want to remain in the lipophilic vehicle at the same time, so absorption is not great
Hydrophilic drug in a lipophilic vehicle don’t absorb very well. Why?
They will make it out of the vehicle but cannot penetrate the stratum corneum because they are hydrophilic
Hydrophilic drug in a hydrophilic vehicle absorb the best of all. True/False?
False
They ain’t going nowhere
What can enhance the absorption of a drug in skin?
Excipients
What are creams?
Semi-solid emulsion of oil and water containing emulsifier and preservative
Creams are cooling and greasy. True/False?
False
They are cooling but not greasy
What is the danger of the preservative in creams?
Allergic reaction
What are ointments?
Semi-solid mix of grease and oil containing soft paraffin
What is the benefit of ointments?
Effective at restricting transepidermal water loss
What is the downside of ointments?
Not cosmetically attractive (very greasy)
What are lotions?
Suspension of medication in water/alcohol/other liquid
What are gels?
Thickened aqueous solutions containing high molecular weight polymers
What is the downside of pastes?
Stiff and difficult to apply
What is the function of emollients?
Enhance hydration of epidermis
For what type of conditions are emollients used?
Dry, scaly conditions
Mainstay for eczema
When are wet wraps frequently used? How are they applied?
For very dry skin
Wrap around previously moisturised skin to lock in moisture
What are the 3 actions of topical steroid upon skin?
Anti-inflammatory
Anti-proliferative
Vasoconstrictive
Name a mild steroid for skin disease
Hydrocortisone
Name a moderate steroid for skin disease
Modrasone
Name a potent steroid for skin disease
Mometasone
Name a very potent steroid for skin disease
Clobetasol
How many grams of steroid are equvalent to 1 fingerprint unit?
0.5g
1 fingertip unit = how many hand areas?
2
What is meant by tachyphylaxis to steroid?
Steroid becomes less effective despite maintained dosage
What conditions is potassium permanganate rinse/soak/bath useful for?
Exudative eczema
Pompholyx
What is pompholyx?
Exudative eczema restricted to hands and feet
Forms watery blisters + severe itch
Name topical antibiotics used for acne
Tetracycline
Clindamycin
Erythromycin
What is the main antibiotic used for rosacea?
Metronidazole
List some antipruritics
Menthol
Capsaicin
Camphor/phenol
Crotamiton
What are keratolytics used for? Name one
Softening keratin (e.g. viral warts, hyperkeratotic disease) Salicylic acid
Emollients can be used for psoraisis along with what other options?
Coal tar
Vitamin D analogues
Keratolytic
Topical steroid
Which cream has been shown to be effective for pre-cancerous and cancerous skin lesions?
Aldara cream
Imiquimod
