Dermatologic Pharm Flashcards
4 major variables affecting cutaneous absorption
Regional — e.g., axilla more permeable than forearm
Concentration gradient — increased concentration —> drug mass/unit time
Dosing schedule — long local t1/2 of skin reservoir may permit QD dosing
Vehicles/occlusion — both can maximize drug penetration
Difference in composition of creams vs. ointments
Creams = mixture of ~half water/half oil with emulsifier (e.g., cetyl alcohol), water evaporates. Spread easily (good for large areas), are well absorbed, and wash off with water
Ointments = mixture of ~20% water in ~80% oil (oil component is made from hydrocarbons such as mineral oil or petroleum jelly). Feel greasy and are “occlusive”, meaning they stay on the surface of skin and are NOT well absorbed
Cream or ointment?: packaged in tub or tube, beter for oozing/“wet” skin conditions
Cream
Cream or ointment?: best used on dry skin since they trap moisture, provide more complete absorption of active ingredient or medication
Ointment
Cream or ointment?: Less likely to cause an allergic reaction
Ointments, because creams contain preservatives
T/F: Hands should be washed for 15-30 seconds using plain soap, although this does not reliably prevent microbial transmission
True
Alcohol-based hand disinfection is easier and faster than soap and water, and is rapidly effective against gram-positive, gram-negative, and viral pathogens. However, it is not effective against _______ so you must use soap and water to protect against transmission of that
C.difficile
Component of moisturizer that forms an oily layer on top of skin that traps water in the skin
Emollient
[common emolllients: petrolatum, lanolin, mineral oil, dimethicone]
Component of moisturizer that draws water into the outer layer of the skin
Humectants
[common humectants: glycerin, lecithin, and propylene glycol]
Component of moisturizer that loosens the bond between the top layer of cells to help dead skin cells fall off, helps the skin retain water, and gives it a smoother softer feel
Horny substance (keratin) softeners
[common agents: urea, alpha hydroxy acids (e.g., lactic, citric, glycolic), allantoin]
3 compounds found in sunscreens and their utility
p-aminobenzoic acid (PABA) and its esters — active in UVB range
Benzophenones — wider 250-360 nm range but less effective than PABA
Dibenzoylmethanes — active in UVA range, particularly useful for conditions such as drug-induced photosensitivity and cutaneous lupus erythematosus
Sunshades are opaque materials that reflect light, the classic example is _____ ______
Titanium dioxide
Broad-spectrum antimicrobial agent widely used in homes and hospitals due to general efficacy on skin (including oral mucosa) and low irritability; low concentrations affect cytoplasmic (inner) cell membrane integrity while high concentrations cause congealing of cytoplasm
Chlorhexidine
Utility of chlorhexidine against bacterial spores
Not sporicidal but prevents development of spores; inhibits spore outgrowth but not germination
Chlorhexidine action against mycobacteria
Mycobacteriostatic (mechanism unknown) but not mycobacteriocidal
Action of chlorhexidine against nonsporulating bacteria
Membrane-active agent, causing protoplast and spheroplast lysis
High concentrations cause precipitation of proteins and nucleic acids
Action of chlorhexidine against yeasts
Membrane-active agent, causing protoplast lysis and intracellular leakage, high concentrations cause intracellular coagulation
Action of chlorhexidine against viruses
Low activity against many viruses; lipid enveloped viruses more sensitive than nonenveloped; effect possibly on viral envelope (e.g., lipid moieties)
Effects of chlorhexidine on protozoa
Has activity against trophozoites, less toward cysts
Protozoan that causes diarrhea in humans, especially in HIV+ pts; oocysts are especially resistant to antiseptics and disinfectants
Coccidia (Cryptosporidium)
Organism considered to be the most resistant to antiseptic and disinfectants, after a chimp developed CJD when neurosurgical tools had been treated with 70% alcohol and formaldehyde vapor and stored for 2 years
Prions (CJD, BSE)
Organism(s) highly resistant to antiseptics and disinfectants that have increased in incidence in hospitalized pts, with CDC recommending using bleach or other EPA-approved agent with sporocidal claims
Spores (Bacillus, C.diff)
The top 3 organisms resistant to antiseptics and disinfectants are prions, coccidia, and spores. What are some others that are considered resistant?
Mycobacteria
Cysts (giardia)
Small non-enveloped viruses (polio)
Trophozoites (acanthamoeba)
Gram-negative non-sporulating bacteria (pseudomonas, providencia)
Fungi (candida, aspergillus)
Large non-enveloped viruses (enterovirus, adenovirus)
Gram positive bacteria (s.aureus, enterococcus)
Lipid enveloped viruses (HIV, HBV)
2 ways in which biofilms affect the utility of disinfectants and/or hand hygiene practices
Limited penetration of disinfectants
Antibiotic neutralization