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SUNSCREENS
Skin damage from radiation is cumulative whether sunburn occurs or not.
Annual incidence: 500,000 cases of basal cell CA occur. 100,000 cases of squamous cell CA occur. 20,000 cases of malignant melanoma
occur.
ULTRAVIOLET RADIATION SPECTRUM
UVA (Longwave Radiation) Range 320-400 nm Erythrogenic activity is weak, however
penetrates dermis Responsible for development of slow natural
tan Most drug-induced photosensitivity rxn occurs UVA may augment the effects of UVB
UVB (Middlewave Radiation) Range 290-320 nm Erythrogenic activity is the highest Produces new pigment formation, sunburn,
Vit D synthesis Responsible for inducing skin cancer
ULTRAVIOLET RADIATION SPECTRUM
UVC (Shortwave or Germicidal Radiation) Range 100-290 nm. Does not reach the surface of the earth. Is emitted from artificial ultraviolet
sources.
ULTRAVIOLET RADIATION SPECTRUM
Long-term hazards of skin damage from radiation:
– Malignancy: • Squamous cell epithelioma• Actinic keratosis• Basal cell carcinoma
– Premature aging• nevus, seborrheic keratosis, solar lentigo• wrinkles, lines, etc
ULTRAVIOLET RADIATION SPECTRUM
SUNSCREEN CLASSIFICATIONS
Physical – Opaque formulations containing:
• titanium dioxide• talc, kaolin• zinc oxide• ferric chloride • icthyol, red petrolatum
– Mechanism: scatters or reflects UV radiation due to large particle size
Chemical– Formulations containing one or more:
• PABA, PABA esters• benzophenones• cinnamates• salicylates• digalloyl trioleate• anthranilates
– Mechanism: absorbs UV radiation
SUNSCREEN CLASSIFICATIONS
Sun Protection Factor (SPF) =
MED of Photoprotected Skin
MED of Unprotected Skin– MED is minimum dose of radiation which
produces erythema – SPFs are determined indoors using xenon
lamps which approximate the spectral quality of UV radiation
SUNSCREENS
SUNSCREENS
Factors which influence effectiveness of SPFs– Difference in skin types.– Thickness of the applied sunscreen.– Time of day.– Altitude: each 1,000 ft increase adds 4% to the intensity of
erythema producing UV radiation; thus intensity is about 20% greater in Pocatello than at sea level.
– Environment: snow/white surfaces reflect 70-90%, and when directly overhead water reflects nearly 100% of UVR.
– Vehicle: determines skin penetration of sunscreen.
SUNSCREENS
Category Skin Type SPF
I Always burns, never tans 15 >
II Burns easily 15
III Burns moderately, (avg caucasian) 10-15
IV Burns minimally, tans well (olive skin”) 6-10
V Rarely burns, tans profusely (brown skin) 4-6
VI Never burns (black skin) none
SUNCREEN AGENTSPABA (Para-aminobenzoic acid) Very effective in the UVB range (200-320 nm).
Most effective in conc of 5% in 70% ethanol. Maximum benefit when applied 60 min prior to exposure
(to ensure penetration and binding to stratum corneum).
Does NOT prevent drug/chemical-induced photosensitivity rxn.
Contact dermatitis can develop. May produce transient drying/stinging from alcohol
content (may be alleviated by adding 10-20% glycerol).
May stain clothing.
SUNCREEN AGENTS
PABA Esters (Padimate A, Padimate O, Glyceryl PABA)
Also very effective in UVB range (280-320) Most effective in conc. 2.5-8% in 65% alcohol May penetrate less effectively than PABA Similar application and adverse effect Less staining
Benzophenones (oxybenzone, dioxybenzone, sulisobensone)
Slightly less effective than PABA. Absorbs from 250-400 nm spectrum (ie, UVA & UVB). Combined with PABA or PABA ester improves
penetration and is superior to either agent used alone (200-400 nm wavelength coverage).
Beneficial in preventing photosensitivity rxns. Contact dermatitis is rare.
SUNCREEN AGENTS
SUNCREEN AGENTS
Cinnamates and Salicylates Minimally effective, absorb UVB spectrum. Generally used in combination with one of the
above.
SUNCREEN AGENTS
Anthranilates Minimally effective, absorbs UVA spectrum
250-322 nm. Usually combined with UVB agent to broaden
spectrum.
USE IN YOUNG CHILDREN
Not recommended in children < 6 mos (due to theoretical concern that percutaneous absorption may be greater and excretory functions may not be mature enough to handle).
No reported cases of toxicity. Recommend clothing (hats, etc).
Tan Accelerators– Contain tyrosine - necessary for production
of melanin, no evidence to support efficacy Sunless Tanners
– Dihydroxyacetone darkens outermost layer– Use at night, sunscreen during day
Tanning Booths– Newer types use light source composed of
95% UVA, < 5% UVB (even 1% may increase incidence of skin cancer).
TANNING
PHOTOSENSITIVITY REACTIONS
Photoallergic Reactions– Radiation alters drug, becomes antigenic or acts
as hapten.– Requires previous exposure.– Not dose related.– Induced by chemically related agents.– Eruption may present as urticarial, eczematous,
bullous, or sunburn-like reactions.– Usually caused by topical agents.
Phototoxic Reactions– Radiation alters drug to toxic form, causes
tissue damage.– Does not require previous exposure.– Dose related.– No cross-sensitivity.– Within several hours of exposure - appears
as exaggerated sunburn.
PHOTOSENSITIVITY REACTIONS
CHOOSING SPF RATING
HIGH SPF SUNSCREENS Can achieve higher SPF by combining
two or more agents. SPF 30 (3%) vs 15 (6%) of radiation
penetrating skin.
SUNSCREEN PRODUCTS
PABA/Ester Oxybenzone Other
Coppertone yes cinnamate
PreSun yes yes
Bull Frog yes cinnamate
Q.T. Quick Tanning cinnamate
Formula 405 Solar Lotion cinnamate
OTC BURN THERAPY
Burn Depth– First degree erythema, no
blistering– Second degree erythema and blisters– Third degree No blisters, leathery
white, mottled– Fourth degree “Charred”
CLASSIFICATION OF BURNS (American Burn Association)
Minor Burns: Second degree burn
Third degree burn
– excludes electrical or inhalation injuries and all poor risk patients.
< 15% BSA
(10% in children)
< 2% BSA not involving eyes, ears, face, hands, feet, or perineum).
Estimation of Burned Area
Rule of nines Body Area Head 9% Arm 9% Leg 18% Anterior Trunk 18% Posterior Trunk 18% Perineum 1%
OTC Treatment of Minor Burns/Sunburns
Ice/cool water Cleansing - water and nonirritating soap Dressings (usually only for second degree burns)
– Nonadherent primary layer of sterile fine-mesh gauze
– Absorbent intermediate layer to draw and store exudate
– Supportive outer layer of rolled gauze bandage
OTC Rx of Minor Burns/SunburnsLocal Anesthetics - short-term relief of pain Benzocaine 5-20% (eg, Americaine®) sensitivity rxn; no
systemic effects Lidocaine 0.5-4% (eg, Bactine®)
– Very low incidence of sensitivity rxn, but systemic toxicity may occur if applied to damaged skin or over large areas
Dibucaine 0.25-1% (eg, Nupercainal® Cream) Tetracaine 1-2% (eg, Pontocaine®) Pramoxine 1% (eg, Tronothane®) Topical Antibiotic (Bacitracin, Polymixin-B Oint.) Protectant (Sterile Petrolatum) - protects against
mechanical irritation and aids rehydration of stratum corneum. ASA for sunburns may help minimize inflammatory response.
POISON IVY/OAK/SUMAC Allergen:
– Urushiol is common to all of these plants– Transmission:
• Contact with resin causes sensitization; – may require as little as 1 mcg.
• Direct contact with plant is NOT necessary.– Plant must be injured/bruised to expose resin;
however requires very little friction to damage plant.
• Contact with resin may occur from shoes, family pet, firewood, etc
– weeks or months after initial exposure.
POISON IVY/OAK/SUMAC
Prevention:– Washing within 5-10 minutes may abort
reaction except in highly sensitive individuals.
– Resin penetrates skin rapidly and binds to skin proteins after which washing is useless
1 mcg may initiate rash in sensitive individual
POISON IVY/OAK/SUMAC
Symptoms:– Lesions are asymmetric and localized to
areas of contact– Itching, followed by erythema, edema,
papules (blisters)• (serum is not contagious)
– Onset usually within 24-48 hrs– Healing may take 2-3 weeks
POISON IVY/OAK/SUMAC
Treatment:– Weeping Lesions:
• Aluminum Acetate (Burow's Soaks) applied 15-30 min BID-QID and/or
• Aveeno bath (colloidal oatmeal) 2-3 times daily for 30 min
• po antihistamines for severe pruritus– AVOID topical: antihistamines, anesthetics, zirconium
– After lesions have dried:• Hydrocortisone CR 0.5% applied 4-6 times daily