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. Malignant melanoma is the tenth most common cause of cancer death in US Non-melanoma (ie squamous + basal) is THE most common human malignancy

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

ULTRAVIOLET RADIATION SPECTRUM 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

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

SUNSCREEN CLASSIFICATIONS Chemical Formulations containing one or more: PABA, PABA esters benzophenones cinnamates salicylates digalloyl trioleate anthranilates Mechanism: absorbs UV radiation

SUNSCREENS 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 SPF is an artificially derived measure of skin protection. One time exposure may not reflect importance of cumulative sub-erythemal doses

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

SUNCREEN AGENTS PABA (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. Problems with PABA: 1. Contact dermatitis 2. Stains clothing 3. Poor substantivity - poor binding to stratum corneum requiring long contact time

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

SUNCREEN AGENTS 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 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).

TANNING Tan Accelerators Sunless Tanners Tanning Booths 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).

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.

PHOTOSENSITIVITY REACTIONS 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.

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. FDA suggests that there is little benefit from SPF formulations > 30. New research suggests that higher SPF may protect cumulative sub-erythemal doses that may prevent UV damage better. Skin becomes sensitized after initial exposure, and thus takes less UV radiation to cause damage and sunburn.

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

Formulation Homomenthyl salicylate 080 Mineral oil 500 Isopropyl myristate 420

Formulation (cream) Suncreen agent 50 Emulsifyer 75 Cetyl alcohol 10 Isopropyl myristate 150 Liquid paraffin 170 Glycerol 30 Water to 1000