SUNSCREENS Skin damage from radiation is cumulative whether sunburn occurs or not. Annual incidence: n 500,000 cases of basal cell CA occur. n 100,000 cases of squamous cell CA occur. n 20,000 cases of malignant melanoma occur.

ULTRAVIOLET RADIATION SPECTRUM UVA (Longwave Radiation) n Range nm n Erythrogenic activity is weak, however penetrates dermis n Responsible for development of slow natural tan n Most drug-induced photosensitivity rxn occurs n UVA may augment the effects of UVB

UVB (Middlewave Radiation) n Range nm n Erythrogenic activity is the highest n Produces new pigment formation, sunburn, Vit D synthesis n Responsible for inducing skin cancer ULTRAVIOLET RADIATION SPECTRUM

UVC (Shortwave or Germicidal Radiation) n Range nm. n Does not reach the surface of the earth. n Is emitted from artificial ultraviolet sources. ULTRAVIOLET RADIATION SPECTRUM

n 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 n 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

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

n 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

n 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) n Very effective in the UVB range ( nm). n Most effective in conc of 5% in 70% ethanol. n Maximum benefit when applied 60 min prior to exposure (to ensure penetration and binding to stratum corneum). n Does NOT prevent drug/chemical-induced photosensitivity rxn. n Contact dermatitis can develop. n May produce transient drying/stinging from alcohol content (may be alleviated by adding 10-20% glycerol). n May stain clothing.

SUNCREEN AGENTS PABA Esters (Padimate A, Padimate O, Glyceryl PABA) n Also very effective in UVB range ( ) n Most effective in conc % in 65% alcohol n May penetrate less effectively than PABA n Similar application and adverse effect n Less staining

Benzophenones (oxybenzone, dioxybenzone, sulisobensone) n Slightly less effective than PABA. n Absorbs from nm spectrum (ie, UVA & UVB). n Combined with PABA or PABA ester improves penetration and is superior to either agent used alone ( nm wavelength coverage). n Beneficial in preventing photosensitivity rxns. n Contact dermatitis is rare. SUNCREEN AGENTS

Cinnamates and Salicylates n Minimally effective, absorb UVB spectrum. n Generally used in combination with one of the above.

SUNCREEN AGENTS Anthranilates n Minimally effective, absorbs UVA spectrum nm. n Usually combined with UVB agent to broaden spectrum.

USE IN YOUNG CHILDREN n 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). n No reported cases of toxicity. n Recommend clothing (hats, etc).

n Tan Accelerators – Contain tyrosine - necessary for production of melanin, no evidence to support efficacy n Sunless Tanners –Dihydroxyacetone darkens outermost layer –Use at night, sunscreen during day n Tanning Booths – Newer types use light source composed of 95% UVA, < 5% UVB (even 1% may increase incidence of skin cancer). TANNING

PHOTOSENSITIVITY REACTIONS n 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.

n 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 n Can achieve higher SPF by combining two or more agents. n SPF 30 (3%) vs 15 (6%) of radiation penetrating skin.

SUNSCREEN PRODUCTS PABA/EsterOxybenzoneOther Coppertone yes cinnamate PreSun yesyes Bull Frog yes cinnamate Q.T. Quick Tanning cinnamate Formula 405 Solar Lotion cinnamate

OTC BURN THERAPY n Burn Depth –First degreeerythema, no blistering –Second degreeerythema and blisters –Third degreeNo blisters, leathery white, mottled –Fourth degree“Charred”

CLASSIFICATION OF BURNS (American Burn Association) Minor Burns: n Second degree burn n 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 ninesBody Area n Head9% n Arm9% n Leg18% n Anterior Trunk18% n Posterior Trunk18% n Perineum 1%

OTC Treatment of Minor Burns/Sunburns n Ice/cool water n Cleansing - water and nonirritating soap n 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 n Homomenthyl salicylate 080 n Mineral oil 500 n Isopropyl myristate 420

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