3 - Sunscreens Flashcards
Drug photosensitisation and photoinduced/photoaggravated dermatoses can be avoided or reduced with sunscreen use
True
UV radiation reaching the Earth’s surface can be divided into:
(1) UVB = 290-320 nm
(2) UVA = 320-400 nm
True
UVA can be further subdivided into:
(1) near UVA or UVA II = 320-340 nm
(2) far UVA or UVA I = 340-400 nm
The UVB blockers include:
(1) Octinoxate (octyl methoxycinnamate)
(2) Octisalate (octyl salicylate)
(3) Octocrylene
(4) Ensulizole (phenylbenzimidazole sulfonic acid)
True
The UVA blockers include:
(1) Oxybenzone (a type of benzophenone)
(2) Meradimate (methyl anthranilate)
(3) Avobenzone (butylmethoxydibenzoylmethane)
(4) Ecamzule (tetraphthalydine dicamphor sulfonic acid)
True
The physical blockers include:
(1) Titanium dioxide
(2) Zinc oxide
True
The Sun Protection Factor (SPF) is defined as the UV radiation required to produce 1 Minimal Erythema Dose (MED) on protected skin after application of 2mg/cm2 of sunscreen / the UV radiation to produce 1 MED on unprotected skin
True
Minimal erythema dose (MED) =
Broad spectrum sunscreen protection is defined as providing protection through the entire spectrum of both UVB and UVA wavelengths
True
UVB = 290-320 nm
UVA = 320-400 nm
Water resistant sunscreen products need to maintain the SPF level after 40 or 80 mins of water immersion
True
Sunscreens have traditionally been divided into:
(1) chemical absorbers
(2) physical blockers
based on their mechanism of action
True
Chemical sunscreens are generally aromatic compounds conjugated with a carbonyl group
True
Chemical sunscreens absorb high intensity UV rays, producing excitation to a high energy state; and upon return to ground state, the result is conversion of the absorbed UV energy into longer lower-energy wavelengths such as infrared radiation (heat)
True
Physical blockers reflect or scatter UV radiation, however microsized forms of physical blockers (also designated as inorganic particulates) also function in part by absorption
True
Para-aminobenzoic acid (PABA) was one of the first UVB chemical sunscreens to be widely available, though historically several problems limited the use of PABA
True
Several problems limited the use of Para-aminobenzoic acid (PABA) as it required an alcoholic vehicle
True (also stained clothing, associated with a subjective stinging and allergic contact dermatitis)
Several problems limited the use of Para-aminobenzoic acid (PABA) as it stained clothing
True (also required an alcoholic vehicle, caused subjective stinging and allergic contact dermatitis)
Several problems limited the use of Para-aminobenzoic acid (PABA) as it caused subjective stinging
True (also required an alcoholic vehicle, stained clothing and caused allergic contact dermatitis)
Several problems limited the use of Para-aminobenzoic acid (PABA) as it caused allergic contact dermatitis
True (also required an alcoholic vehicle, stained clothing and caused subjective stinging)
Padimate O (octyl dimethyl PABA) replaced the original para-aminobenzoic acid (PABA) as it had greater compatibility in a variety of cosmetic vehicles and had a lower potential for staining or other adverse reactions
True (UVB chemical sunscreen)
Despite being a potent UVB absorber, problems with PABA formulations in general have limited their use
True (both PABA and Padimate O, even though Padimate O is the most potent FDA approved UVB absorber)
Padimate O (octyl dimethyl PABA) is the most potent FDA approved UVB absorber
True (although the decline in PABA formulations due to allergic contact dermatitis, along with the demand for higher SPF products led to the incorporation of multiple active ingredients in a single product to achieve the desired SPF) - The cinnamates such as Octinoxate (octyl methoxycinnamate) largely replaced PABA derivatives such as Padimate O as the next most potent UVB absorber
The cinnamates such as Octinoxate (octyl methoxycinnamate) largely replaced PABA derivatives such as Padimate O as the next most potent UVB absorber
True
Octinoxate (octyl methoxycinnamate) is the most frequently used sunscreen ingredient
True (UVB absorber)
Octisalate (Octyl salicylate) is used to augment the UVB protection in a sunscreen as salicylates are weak UVB absorbers and are generally used in combination with other UV sunscreens
True
Octocrylene is a UVB absorber used in combination with other UV absorbers to achieve higher SPF formulations
True
Ensulizole (phenylbenzimidazole sulfonic acid) is a water soluble UVB absorber and is used in products formulated to feel lighter and less oily, such as in daily-use cosmetic moisturisers
True (most chemical sunscreen ingredients are oils soluble in the oil phase of emulsion systems which account for the heavy, greasy properties of many of these products)
Although benzophenones are primarily UVB absorbers, it’s derivative Oxybenzone also absorbs well through the near UVA/UVA II spectrum (320-340 nm), therefore benzophenones significantly augment the UVB protection of a sunscreen product while expanding into UVA coverage when used in a given formulation
True
Meradimate (methyl anthranilate) is a weak UVB filter that absorbs mainly in the near UVA II (320-340 nm) portion of the spectrum
True (it is a less effective sunscreen ingredient and is less widely used)
Avobenzone (butylmethoxydibenzoylmethane) provides superior protection through a large portion of the UVA spectrum including majority of the far UVA/UVA I spectrum (340-400 nm)
True (although photostability is a problem with Avobenzone, and it also has the potential to degrade other sunscreen ingredients in products such as the potent UVB cinnamate absorber octinoxate)
The photoinstability of Avobenzone can be offset by combining it with Octocrylene (used for photostability)
True
Octocrylene is a UVB absorber used in combination with other UV absorbers to achieve photostability
True (classically combined with the UVA absorber Avobenzone to offset Avobenzone’s photoinstability)
Ecamsule (tetraphthalydine dicamphor sulfonic acid) is a UVA filter with broad absorption profile from 290-390 nm (UVB 290-320 nm, near UVA 320-340 nm and far UVA 340-400 nm) with peak absorption at 345 nm (far UVA wavelength)
True
Poor cosmetic acceptance limited the widespread use of the physical blockers titanium dioxide and zinc oxide, until microsized forms became available
True
The physical blockers titanium dioxide and zinc oxide are inorganic particulate sunscreens which are reactive and poorly soluble and do not show significant skin penetration
True
The ideal sunscreen agent would be:
(1) chemically inert
(2) safe
(3) reflect through the full UV spectrum
True (the physical blockers titanium dioxide and zinc oxide)
By reducing the particle size of titanium dioxide to make it more aesthetically acceptable, titanium dioxide functions more by absorption and not simply by blocking (reflecting and scattering) UV radiation, therefore making titanium dioxide less effective in the UVA range than an opaque physical blocker
True (although this microsized ingredient can still be classified as a broad-spectrum agent)
Titanium dioxide causes a whitening effect on the skin secondary to pigment residue
True (the net effect might be that the user is inclined to apply the product less heavily, thus effectively lowering the SPF) - hybrid products using a combination of chemical UV absorbers with inorganic particulate blockers may represent a practical compromise
Zinc oxide is a physical blocker which offers the same advantages and disadvantages as titanium dioxide, although zinc oxide has more superior far UVA/UVA I protection (specifically 340-380 mm spectrum) than for titanium dioxide, thereby providing more full spectrum protection
True