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- Gonzalez, Helena, 1971, et al.
(author)
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Percutaneous absorption of the sunscreen benzophenone-3 after repeated whole-body applications, with and without ultraviolet irradiation
- 2006
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In: Br J Dermatol. - : Oxford University Press (OUP). - 0007-0963. ; 154:2, s. 337-40
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Journal article (peer-reviewed)abstract
- BACKGROUND: Benzophenone-3 (BZ-3; 2-hydroxy-4-methoxybenzophenone, oxybenzone) is commonly used to absorb ultraviolet (UV) radiation. BZ-3 penetrates the skin and can be found in the urine. The amount varies between 0.4% and 2%. This seems to be the main metabolic pathway in rats. OBJECTIVES: To investigate the total amount of BZ-3 excreted in the urine after repeated topical whole-body applications of a sunscreen and to see if UV radiation has any effect on the amount excreted. METHODS: Twenty-five volunteers applied a commercially available sunscreen containing 4% BZ-3 morning and night for 5 days. Their urine was measured during those 5 days and during a further 5 days after the last application. They were divided into groups A (unirradiated) and B. Group B received UV radiation according to skin type: UVA between 400 and 707 J cm(-2), and UVB between 0.46 and 2.0 J cm(-2). BZ-3 in urine was analysed with a high-performance liquid chromatography method. RESULTS: The volunteers excreted 1.2-8.7% (mean 3.7%) of the total amount of BZ-3 applied. There was no significant difference between the two groups (P < 0.99, t-test). CONCLUSIONS: We show that a large amount of BZ-3 is absorbed. BZ-3 is accumulated in the body as the volunteers excreted BZ-3 5 days after the last application.
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| 2. |
- Gonzalez, Helena, 1971, et al.
(author)
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Photostability of commercial sunscreens upon sun exposure and irradiation by ultraviolet lamps
- 2007
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In: BMC Dermatol. - 1471-5945. ; 7
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Journal article (peer-reviewed)abstract
- BACKGROUND: Sunscreens are being widely used to reduce exposure to harmful ultraviolet (UV) radiation. The fact that some sunscreens are photounstable has been known for many years. Since the UV-absorbing ingredients of sunscreens may be photounstable, especially in the long wavelength region, it is of great interest to determine their degradation during exposure to UV radiation. Our aim was to investigate the photostability of seven commercial sunscreen products after natural UV exposure (UVnat) and artificial UV exposure (UVart). METHODS: Seven commercial sunscreens were studied with absorption spectroscopy. Sunscreen product, 0.5 mg/cm2, was placed between plates of silica. The area under the curve (AUC) in the spectrum was calculated for UVA (320-400 nm), UVA1 (340-400 nm), UVA2 (320-340 nm) and UVB (290-320 nm) before (AUCbefore) and after (AUCafter) UVart (980 kJ/m2 UVA and 12 kJ/m2 of UVB) and before and after UVnat. If theAUC Index (AUCI), defined as AUCI = AUCafter/AUCbefore, was > 0.80, the sunscreen was considered photostable. RESULTS: Three sunscreens were unstable after 90 min of UVnat; in the UVA range the AUCI was between 0.41 and 0.76. In the UVB range one of these sunscreens was unstable with an AUCI of 0.75 after 90 min. Three sunscreens were photostable after 120 min of UVnat; in the UVA range the AUCI was between 0.85 and 0.99 and in the UVB range between 0.92 and 1.0. One sunscreen showed in the UVA range an AUCI of 0.87 after UVnat but an AUCI of 0.72 after UVart. Five of the sunscreens were stable in the UVB region. CONCLUSION: The present study shows that several sunscreens are photounstable in the UVA range after UVnat and UVart. There is a need for a standardized method to measure photostability, and the photostability should be marked on the sunscreen product.
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| 4. |
- Gonzalez, Helena, 1971
(author)
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Studies of Sunscreens: Percutaneous Absorption of Benzophenone-3 and Photostability
- 2006
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Doctoral thesis (other academic/artistic)abstract
- Studies of Sunscreens: Percutaneous Absorption of Benzophenone-3 and Photostability Helena Gonzalez Department of Dermatology and Venereology Institute of Clinical Sciences The Sahlgrenska Academy at Göteborg University Göteborg, Sweden Abstract Aim: To learn more about percutaneous absorption of the photoactive compound benzophenone-3 (BZ-3) and to study the excretion pattern of BZ-3 and its metabolite dihydroxy benzophenone (DHB). We also got the opportunity to develop a reverse-phase HPLC method to analyze BZ-3 and DHB. The photostability of seven commercial sunscreens was also studied. Material and methods: Paper I: 11 participants applied a sunscreen, 2 mg/cm2, containing 4% BZ-3. They collected urine for 48 hours after the application. Paper II: 26 participants applied a sunscreen, 2 mg/cm2, containing 4% BZ-3 morning and night for five days. Half of the participants were exposed to UV radiation (UVR). They collected urine for the five days the sunscreen was applied and an additional five days after the last application. Paper III: The assay uses: solid-phase extraction with C8 columns; a Genesis C18 column (4.6 mm x 150 mm ); a gradient acetonitrile-water mobile phase; a UV-detector set at 287 nm. Paper IV: Seven commercial sunscreens were studied with absorption spectrophotometry. Sunscreen product, 0.5 mg/cm2, was placed between plates of silica. The area under the curve (AUC) in the spectrum was calculated for the different UV regions. AUC before (AUCbefore) and after (AUCafter) artificial UV exposure and before and after natural UV exposure were calculated. If the AUC Index (AUCI), defined as AUCI=AUCafter/AUCbefore, was > 0.80, the sunscreen was considered photostable. Results: Paper I: The average total amount excreted was 11 mg, median 9.8 mg, which is approximately 0.4% of the applied amount BZ-3. Paper II: The volunteers excreted 1.2-8.7% BZ-3 of the total applied amount. The mean value found was 3.7%. There was no significant difference between the two groups; p<0.99. Paper III: The assay was linear r2 >0.99, with detection limits for BZ-3 and DHB of 0.01 µmol/l and 0.16 µmol/l respectively. Relative standard deviation was less than 10% for BZ-3 and less than 13% for DHB. The excretion pattern varied among the human volunteers, different patterns were discerned among the individuals. Paper IV: Three sunscreens were unstable after 90 min of natural UV, in the UVA range the AUCI was between 0.41 and 0.76. In the UVB range, one of these sunscreens was unstable with an AUCI of 0.75 after 90 min. Three sunscreens were photostable after 120 min of natural UV, in the UVA range the AUCI was between 0.85 and 0.99 and in the UVB range between 0.92 and 1.0. Conclusions: Paper I: BZ-3 is absorbed by the skin and excreted in the urine after one topical application of a sunscreen containing 4% BZ-3. There are individual differences in the amount excreted and in the excretion pattern. Paper II: Repeated topical applications of a sunscreen containing 4% BZ-3 lead to a higher excretion of BZ-3. There was no statistical difference after exposure to UVR. Paper III: The developed reverse-phase HPLC-method was reliable and suitable to handle a large number of samples. BZ-3 and DHB were excreted in a similar pattern. Paper IV: Three of the seven investigated sunscreens were photounstable in the UVA region. The combination ethylhexyl methoxycinnamate and butyl methoxydibenzoylmethane was unstable regardless of which other photoactive compound that was included in the sunscreen. Key words: benzophenone-3, dihydroxy benzophenone, sunscreens, UV radiation, reverse-phase HPLC, photostability
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| 5. |
- Halldin, Christina, 1957, et al.
(author)
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Nerve blocks enable adequate pain relief during topical photodynamic therapy of field cancerization on the forehead and scalp
- 2009
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In: British Journal of Dermatology. - 1365-2133. ; 160:4, s. 795-800
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Journal article (peer-reviewed)abstract
- BACKGROUND: Topical photodynamic therapy (PDT) is an effective method when treating extensive areas of sun-damaged skin with multiple actinic keratoses (AKs) (field cancerization) on areas such as the forehead and scalp, and offers excellent cosmetic outcome. The major side-effect of PDT is the pain experienced during treatment. OBJECTIVES: To investigate whether nerve blocks could provide adequate pain relief during PDT of AKs on the forehead and scalp. METHODS: Ten men with symmetrically distributed and extensive AKs on the forehead and scalp were included in the study. Prior to PDT one side of the forehead and scalp was anaesthetized by nerve blocks while the other side served as control. RESULTS: The mean visual analogue scale (VAS) score on the anaesthetized side was 1 compared with 6.4 on the nonanaesthetized side during PDT. This difference was significant (P<0.0001), implying that nerve blocks reduce VAS scores during PDT. CONCLUSIONS: The results of the study support the use of nerve blocks as pain relief during PDT of field cancerization on the forehead and scalp, although individual considerations must be taken into account to find the most adequate pain-relieving method for each patient.
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