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