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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 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 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 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. 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 – 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. SUNSCREEN PRODUCTS PABA/Ester Oxybenzone Other Coppertone PreSun yes Bull Frog Q.T. Quick Tanning Formula 405 Solar Lotion yes cinnamate yes yes cinnamate cinnamate cinnamate OTC BURN THERAPY Burn Depth – First degree – Second degree – Third degree – Fourth degree erythema, no blistering erythema and blisters No blisters, leathery white, mottled “Charred” CLASSIFICATION OF BURNS (American Burn Association) Minor Burns: Second degree burn < 15% BSA (10% in children) Third degree burn < 2% BSA not involving eyes, ears, face, hands, feet, or perineum). – excludes electrical or inhalation injuries and all poor risk patients. Estimation of Burned Area Rule of nines Head Arm Leg Anterior Trunk Posterior Trunk Perineum Body Area 9% 9% 18% 18% 18% 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 finemesh gauze – Absorbent intermediate layer to draw and store exudate – Supportive outer layer of rolled gauze bandage Formulation Homomenthyl salicylate Mineral oil Isopropyl myristate 080 500 420 Formulation (cream) Suncreen agent Emulsifyer Cetyl alcohol Isopropyl myristate Liquid paraffin Glycerol Water to 50 75 10 150 170 30 1000