Phototoxicity and photoallergy
Photosensitivity may be phototoxic or photoallergic. Phototoxicity is much more common. There are 2 types of phototoxicity: photodynamic, which requires oxygen, and nonphotodynamic, which does not. Reactions induced by porphyrin molecules, coal tar derivatives, and many drugs are photodynamic. The reaction induced by psoralens, for the most part, is nonphotodynamic. Acute phototoxic reactions are characterized by erythema and edema followed by hyperpigmentation. Long-term ultraviolet phototoxicity results in chronic sun damage and skin cancer formation. Also, certain chemicals such as psoralen molecules and coal tar are photocarcinogenic. Phototoxic reactions to certain drugs produce unusual clinical patterns, that is lichenoid eruptions, dyschromia, photo-onycholysis, and pseudoporphyria. Photoallergy is an uncommon acquired altered reactivity dependent on an immediate antibody or a delayed cell mediated reaction. Solar urticaria is an example of the former, whereas photoallergy to exogenous chemicals is an example of the latter. Photoallergy to systemic drugs does occur but is difficult to characterize. The action spectrum for photoreactions to exogenous agents usually at least includes the ultraviolet A rays for both phototoxicity and photoallergy.
Available from: Eric Duell
- "Particular medications that are described as " photosensitizing, " including those with known ability to induce either a phototoxic or photoallergic reaction upon UV exposure, increase the vulnerability of the skin to UVinduced damage that can lead to the development of NMSC (Stern, 1998). Such medications belong to a variety of pharmacological classes by composition and are used for an array of diverse conditions ranging from treatment of acute bacterial infections to long-term hypertension control (Gould et al., 1995; Bellaney et al., 1996; Stern 1998; Epstein 1999). "
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ABSTRACT: It is well-known that ultraviolet (UV) light exposure and a sun sensitive phenotype are risk factors for the development of non-melanoma skin cancer (NMSC), including basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). In this New Hampshire population-based case-control study, we collected data from 5,072 individuals, including histologically-confirmed cases of BCC and SCC, and controls via a personal interview to investigate possible associations between photosensitizing medication use and NMSC. After adjustment for potentially confounding factors (e.g. lifetime number of painful sunburns), we found a modest increase in risk of SCC (OR=1.2, 95% CI=1.0-1.4) and BCC (OR=1.2, 95% CI=0.9-1.5), in particular early-onset BCC, (≤ 50 years of age) (OR=1.5, 95% CI=1.1-2.1) associated with photosensitizing medication use. For SCC the association was strongest amongst those with tendency to sunburn rather than tan. We also specifically found associations with BCC, and especially early-onset BCC, and photosensitizing antimicrobials. In conclusion, certain commonly prescribed photosensitizing medications may enhance the risk of developing SCC, especially in individuals with a sun sensitive phenotype, and may increase the risk of developing BCC and incidence of BCC at a younger age.Journal of Investigative Dermatology accepted article preview online, 23 January 2013; doi:10.1038/jid.2013.33.
Available from: Christof Schäfer
- "Photosensitivity occurs both as a phototoxic, non-immunologic phenomenon and as a photoallergic, immune-dependent reaction. The much more common phototoxicity can be subdivided into a photodynamic type, which requires oxygen, and a nonphotodynamic, which does not . The majority of photosensitising drugs have an action spectrum within UVA. "
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ABSTRACT: Modern radiotherapy (RT) reduces the side effects at organ at risk. However, skin toxicity is still a major problem in many entities, especially head and neck cancer. Some substances like chemotherapy provide a risk of increased side effects or can induce a "recall phenomenon" imitating acute RT-reactions months after RT. Moreover, some phototoxic drugs seem to enhance side effects of radiotherapy while others do not. We report a case of "radiation recall dermatitis" (RRD) one year after RT as a result of taking hypericin (St. John's wort).
A 65 year old man with completely resected squamous cell carcinoma of the epiglottis received an adjuvant locoregional RT up to a dose of 64.8 Gy. The patient took hypericin during and months after RT without informing the physician. During radiotherapy the patient developed unusual intensive skin reactions. Five months after RT the skin was completely bland at the first follow up. However, half a year later the patient presented erythema, but only within the area of previously irradiated skin. After local application of a steroid cream the symptoms diminished but returned after the end of steroid therapy. The anamnesis disclosed that the patient took hypericin because of depressive mood. We recommended to discontinue hypericin and the symptoms disappeared afterward.
Several drugs are able to enhance skin toxicity of RT. Furthermore, the effect of RRD is well known especially for chemotherapy agents such as taxans. However, the underlying mechanisms are not known in detail so far. Moreover, it is unknown whether photosensitising drugs can also be considered to increase radiation sensitivity and whether a recall phenomenon is possible. The first report of a hypericin induced RRD and review of the literature are presented. In clinical practise many interactions between drugs and radiotherapy were not noticed and if registered not published. We recommend to ask especially for complementary or alternative drugs because patients tend to conceal such medication as harmless.
Available from: Elisabete Pereira dos Santos
- "A fotosensibilidade pode gerar reações fotoalérgicas e fototóxicas. Estas últimas ocorrem geralmente quando uma substância fotoreativa é exposta à radiação solar e a radiações de comprimento de onda de 200 a 400 nm, que são as principais responsáveis por esta resposta cutânea (Epstein, 1999). Os principais efeitos destas reações são eritemas, edemas, esfoliações e hiperpigmentação. "
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ABSTRACT: A utilização de extratos vegetais em produtos farmacêuticos e cosméticos tem mostrado ser uma tendência mundial e cresceu substancialmente nas duas últimas décadas. No entanto, há ainda poucos relatos na literatura com relação à atividade mutagênica ou fototóxica de extratos vegetais. No presente trabalho foi avaliada a atividade fototóxica e o “screening” mutagênico de extratos fluidos e secos de própolis, Aloe spp. e Hamamelis virginiana. Na investigação de fototoxicidade foram realizados ensaios microbiológicos, utilizando cepas de Candida albicans e Saccharomyces cerevisiae, bem como ensaios biológicos com cobaias albinos. Extratos etanólicos de Ruta graveolens e Citrus spp., além de 8-metoxipsoraleno (fármaco sintético padrão), foram usados como controles positivos em ambos os testes. A atividade mutagênica foi avaliada qualitativamente segundo o “spot test” descrito por Maron & Ames, com cepas de Salmonella typhimurium TA97, TA98, TA100 e TA102, empregando como controle positivo o óxido de 4-nitroquinolina. Não foi observada atividade fototóxica, em ambos os ensaios realizados, para qualquer dos extratos. O ensaio microbiológico demonstrou uma atividade fungistática ou fungicida nos extratos secos de hamamélis. Os resultados obtidos nos ensaios microbiológicos com a levedura S. cerevisiae indicam que este microrganismo apresentou eficiência no procedimento de “screening” de atividade fototóxica comparável à obtida com C. albicans. Os extratos vegetais não apresentaram atividade mutagênica nos ensaios preliminares realizados. Palavras-chave: Aloe spp., Hamamelis virginiana, própolis, fototoxicidade, mutagenicidade.
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