Kruse DSA: Dermatologic Pharmacology Flashcards
Which vehicles are best at stopping evaporation from the surface of the skin?
-pastes, creams, and ointments
In which area of the body is drug penetration highest?
-face, scalp, scrotum, in intertriginous areas, and especially in the perineum
why do children experience a greater systemic dose than adults?
-children have a greater surface area to mass ratio than adults
Bacitracin and gamicidin
- MOA: inhibits cell wall synth (bacitracin); increases permeability of cell wall (gramcidin)
- active against gram + organisms like strept, pneumo, and staph, and most anaerobic occi, neisseria, tetanuc bacilli, and diptheria bacilli
- systemic toxicity limits the use of gramcidin to topical applications, usually in combo with other abx like neomycn, polymysin, bacitracin, and nystatin
Mupirocin (pseudomonic acid A)
- MOA: inhibits ptn synth (binds to isoleucyl-tRNA synthetase)
- effective against most gram + aerobic bacteria, including MRSA
- effective tx for impetigo caused by S aureus and group A strep
Retapamulin
- MOA: binds to ribosomal 50S subunit and inhibits normal bacterial ptn iosynthesis
- effective against group A B hemolytic streptococci and S aureus including MRSA
Polymyxin B sulfate
- MOA: increases permaility of cell wall membrane
- effective against gram - organisms including P aeruginosa, E. coli, enterobacter, klebsiella
- Neosporin maing ingredient
- high levels can cause neruotoxicity and nepthrotoxicity (rare)
Neomycin and gentamicin
- MOA: irreversibly binds 30S subunit and inhibits ptn synthesis
- good for gram - organisms
- excreted primarily in urine; renal failure may cause nephrotoxicity, neurotoxicity, ototoxicity if serum levels become detectable (rare)
Clindamycin
- MOA: inhibits ptn synthesis by reversibly binding to 50S ribosomal subunit
- approved for tx of serious infections due to S. aureus (MRSA)
Erythromycin
- MOA: inhibits ptn synthesis by reverisbly binding to 50 S ribosomal subunit
- complication include development of antibiotic resistance in staph; if this occurs, discontinue topic tx and begin systemic antibiotic therapy
Metronidazole
- MOA: inhibition of nucleic acid synthesis; anti-inflammatory effects
- effective in x of acne rosacea
- not recommended during preggo or nursing due to carcinogenic nature
Sodium sufacetamide
- MOA: inhibits P. acnes by competitive inhibition of p-aminobenzoic acid utilization and inhibits bacterial folic acid synthesis
- contraindicated in pts with sensitivity to sulfonamides
MOA for azoles as topical antifungal preparations
-inhibit synth of ergosterol (an esential component of the fungal cell membrane) by inhibiting fungal cyt p 450s
What are Azoles used for?
-tinea infections
What are the protoypical azoled used for almost all candidiasis infections that can be treated topically?
-Cotimazole and miconazole
Ciclopirox olamine
- broad spectrum antimycotic agent
- MOA: inhibits the uptake of precursors of macromolecular synthesis
- used to treat topical dermatomycosis, candidiasis, and tinea versicolor and mild to moderate onychomycosis of fingernails and toenails at higher topical concentrations
- poor efficacy
Allylamines
- Terbinafine, and naftifine
- MOA: inhibits squalene epoxidase, a key enzyme in ergosterol biosynthesis
- effective for topical tx of tinea corporis, tinea cruris, and tinea pedis
Butenafine
-similar to allylamines in MOA and use
Tolnaftate
- effective in the tx of most cutaneous mycoses but is ineffective against candida
- used for tinea pedis, cruris, and corporis
- exact antifungal MOA unkown
Nystatin and amphotericin B
-MOA: binds to ergosterol in fungal cell membrane and alters membrane permeability, leading to the loss of potassium and other cell constituents (ineffective against dermatophytes)
What is nystatin used for?
-tx of oral candidiasis
What can cause yellowing of the skin if used in a cream vehicle?
- Amphoterecin B
- also causes infusion related toxicity and cumulative organ toxicity, which has given this drug the nickname “ampho-terrible”
Azoles as oral antifungal agents
- Itraconazole and fluconazole are protoypes
- lots of drug-drug interactions by decreasing rate of drug metabolism (statins…. rhabdomyolysis due to CYP inhibition)
Griseofulvin
- MOA: inhibits fungal cell mitosis at metaphase and binds to human keratin, making it resistant to fungal invasion
- treats dermatophyte infections but not candida infections
- serious adverse effects are rare
- induces hepatic CYPs
- Less overall effectiveness in treating onychomycosis compared to itraconazole or terbinafine
Terbinafine
- high first pass metabolism for oral preps; accumulates in skin, nails, and fat
- oral preps effective for tinea corporis, capitis, and onychomycosis (better than griseofulvin)
What are the topical antiviral agents?
- acyclovir, valacyclovir, penciclovir, famciclovir
- synthetic guanine analogs with inhibitory activity against members of the herpesvirus family
MOA of topical antiviral agents?
- converted to pharmacologicaly active triphosphate metabolites and inhibit viral DNA synthesis and viral replication
- oral preps available for herpes labialis
- topical preps for recurrent orolabial HSV infaction in IC patients
- adverse local rxns to topical preps may include pruritus and mild pain with transient stinging or burning
Docosanol
- MOA: inhibits fusion between the plasma membrane and the HSV envelope, thereby preventing viral entry and replication
- when applied within 12 hours of the onset of prodromal symptoms, five times daily, median healing time was shortened by 18 hours compared with placebo in recurrent orolabial herpes
Imiquimod
-tx of external genital and perianal warts in adults, actinic keratoses on the face and scalp, biopsy proven primary BCC’s on the trunk, neck, and extremities
MOA of Imiquimod
-unknown,
adverse effects of Imiquimod
-local inflammation, pruritus, erythema, superficial erosion (percutaneous absorption is minimal)
Tacrolimus
- macrolide immunosuppressant benefical in the tx of atopic dermatitis
- traditionally used to prevent heart, liver, and kidney allograft rejection due to potent immunosuppressive activity
MOA of Tacrolimus
-inhibit T- lymphocyte activation and prevent release of inflammatory cytokines and mediators from mast cells
adverse effects of tacrolimus
-transient erythema, burning, and pruritus
Pimecrolimus
-similar MOA and adverse effects as tacrolimus
Tretinoin
-acid form of Vit A
-unknown MOA
-metabolized by liver and excreted in bile and urine
inital therapy may aggravate acne but continual tx increases the likelihood of optimal clinical improvement
Common adverse effects of tretinoin
- erythema, mild peeling, and dryness
- pts advised to avoid or minimize sun exposure
Adapalene
- photochemically more stable and less irritating than tretinoin
- used to tx mild to moderate acne vulgaris
Tazarotene
-approved for psoriasis, photoaging, acne
Are topical preps of retinoids good for preggo?
- no
- women should receive contraceptive counseling before use because of teratogenic effects
The one oral drug for acne
- Isotretinoin
- only for severe cystic acne
MOA for isotretinoin
- reduces sebaceous gland size and reduces sebum production
- hepatic metabolism… highly prn bound