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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)
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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)
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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)
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Range 100-290 nm.
Does not reach the surface of the earth.
Is emitted from artificial ultraviolet
sources.
ULTRAVIOLET RADIATION
SPECTRUM
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Long-term hazards of skin damage
from radiation:
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Malignancy:
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Squamous cell epithelioma
Actinic keratosis
Basal cell carcinoma
Premature aging
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nevus, seborrheic keratosis, solar lentigo
wrinkles, lines, etc
SUNSCREEN CLASSIFICATIONS
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Physical
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Opaque formulations containing:
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titanium dioxide
talc, kaolin
zinc oxide
ferric chloride
icthyol, red petrolatum
Mechanism: scatters or reflects UV
radiation due to large particle size
SUNSCREEN CLASSIFICATIONS
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Chemical
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Formulations containing one or more:
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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
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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.
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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)
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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).
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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,
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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
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Minimally effective, absorb UVB spectrum.
Generally used in combination with one of the
above.
SUNCREEN AGENTS
Anthranilates
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Minimally effective, absorbs UVA spectrum
250-322 nm.
Usually combined with UVB agent to broaden
spectrum.
USE IN YOUNG CHILDREN
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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).
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No reported cases of toxicity.
Recommend clothing (hats, etc).
TANNING
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Tan Accelerators
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Contain tyrosine - necessary for production
of melanin, no evidence to support efficacy
Sunless Tanners
– Dihydroxyacetone darkens outermost layer
– Use at night, sunscreen during day
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Tanning Booths
–
Newer types use light source composed of
95% UVA, < 5% UVB (even 1% may
increase incidence of skin cancer).
PHOTOSENSITIVITY REACTIONS
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Photoallergic Reactions
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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
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Phototoxic Reactions
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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
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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:
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Second degree burn
< 15% BSA
(10% in children)
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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
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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
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Homomenthyl salicylate
Mineral oil
Isopropyl myristate
080
500
420
Formulation (cream)
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Suncreen agent
Emulsifyer
Cetyl alcohol
Isopropyl myristate
Liquid paraffin
Glycerol
Water to
50
75
10
150
170
30
1000